Merge pull request #905 from ispyisail/harden/crash-reporter

Harden the crash reporter: keep every dump, and say what crashed

CMakeLists.txt

@@ -101,6 +101,21 @@ else()
     message(STATUS "Qt Qml module not available: JavaScript scripting (--run) disabled")
 endif()
 
+# The crash handler writes a backtrace into the dump. Detecting this with
+# __has_include(<execinfo.h>) is not enough: the header is present on FreeBSD
+# too, but backtrace() lives in a separate libexecinfo there, so the compile
+# succeeds and the link fails. FindBacktrace resolves both the header and
+# whichever library actually provides the symbol, so gate on it instead - see
+# the QET_CRASH_BACKTRACE guard in sources/logging/crashhandler.cpp.
+find_package(Backtrace QUIET)
+if(Backtrace_FOUND)
+    list(APPEND QET_PRIVATE_LIBRARIES ${Backtrace_LIBRARIES})
+    include_directories(${Backtrace_INCLUDE_DIRS})
+    add_compile_definitions(QET_CRASH_BACKTRACE)
+else()
+    message(STATUS "backtrace() not available: crash dumps will carry the log ring without a backtrace")
+endif()
+
 find_package(SQLite3 REQUIRED)
 
 # CMake < 4.3 only creates the SQLite::SQLite3 target (no SQLite3::SQLite3

sources/editor/ui/qetelementeditor.cpp

@@ -23,6 +23,7 @@
 #include "../elementview.h"
 #include "../../qetmessagebox.h"
 #include "../../qetapp.h"
+#include "../../qetmainwindow.h"
 #include "../../recentfiles.h"
 #include "../graphicspart/customelementpart.h"
 #include "../elementitemeditor.h"
@@ -905,6 +906,13 @@ void QETElementEditor::openElement(const QString &filepath)
  */
 void QETElementEditor::closeEvent(QCloseEvent *qce)
 {
+		//This editor is a plain QMainWindow, not a QETMainWindow, so the
+		//guard QETMainWindow::event() applies to the other editors is
+		//applied here instead -- before canClose(), which itself opens a
+		//modal dialog.
+	if (QETMainWindow::refuseCloseWhileModal(qce)) {
+		return;
+	}
 	if (canClose()) {
 		writeSettings();
 		setAttribute(Qt::WA_DeleteOnClose);

sources/logging/crashhandler.cpp

@@ -36,6 +36,13 @@
 #include <csignal>
 #include <fcntl.h>
 #include <unistd.h>
+	// QET_CRASH_BACKTRACE is defined by CMake, via find_package(Backtrace),
+	// not by probing for the header here. <execinfo.h> exists on FreeBSD as
+	// well, but backtrace() is in a separate libexecinfo there, so a header
+	// probe compiles and then fails to link.
+#ifdef QET_CRASH_BACKTRACE
+#include <execinfo.h>
+#endif
 #endif
 
 namespace {
@@ -64,6 +71,14 @@ char g_altstack[65536];
 
 const int kHandledSignals[] = {SIGSEGV, SIGABRT, SIGBUS, SIGFPE, SIGILL};
 
+#ifdef QET_CRASH_BACKTRACE
+// Preallocated here for the same reason as everything else in this block:
+// backtrace() fills a caller-supplied array, so it needs no heap of its
+// own, and backtrace_symbols_fd() writes straight to the fd (unlike
+// backtrace_symbols(), which mallocs and is therefore unusable here).
+void *g_backtrace_frames[64];
+#endif
+
 void restoreDefaultAndReraise(int sig)
 {
 	struct sigaction sa {};
@@ -85,16 +100,63 @@ void signalHandler(int sig)
 		return;
 	}
 
-	// open/write/close are all on the POSIX async-signal-safe function
-	// list; nothing else is called here.
+	// open/write/close, and backtrace_symbols_fd, are all on the POSIX
+	// async-signal-safe function list; nothing else is called here.
+	//
+	// Async-signal-safe is not the same as lock-free, which is why the
+	// order below matters. backtrace() unwinds through libgcc, which calls
+	// dl_iterate_phdr and takes the loader lock. Warming it in install()
+	// removes the allocation, not the lock -- so a crash that happens
+	// inside dlopen() (Qt plugin loading), or on a corrupted heap or
+	// stack, can leave this handler deadlocked or faulting a second time
+	// at the backtrace. Everything cheaper and more valuable is therefore
+	// written and flushed first: header, signal, then the log ring. If the
+	// backtrace never completes, the dump is still there and still useful.
 	const int fd = ::open(g_dump_path, O_WRONLY | O_CREAT | O_TRUNC, 0600);
 	if (fd >= 0) {
 		if (g_header_len > 0) {
 			::write(fd, g_header, static_cast<size_t>(g_header_len));
 		}
+
+		// Which signal killed it. The header is built once at install()
+		// and is therefore identical for every crash, so without this the
+		// dump never said what actually happened -- SIGSEGV and SIGABRT
+		// point at very different bugs.
+		char line[64];
+		int len = 0;
+		const char kSignalLabel[] = "Signal: ";
+		for (unsigned i = 0 ; i < sizeof(kSignalLabel) - 1 ; ++i) {
+			line[len++] = kSignalLabel[i];
+		}
+		len += CrashHandler::formatInt(line + len, static_cast<int>(sizeof(line)) - len - 1, sig);
+		line[len++] = '\n';
+		::write(fd, line, static_cast<size_t>(len));
+
+		// The ring first: it is the part that says what the program was
+		// doing, it costs one write, and it takes no lock.
+		const char kRingLabel[] = "--- log ---\n";
+		::write(fd, kRingLabel, sizeof(kRingLabel) - 1);
 		if (g_ring) {
 			g_ring->dumpToFd(fd);
 		}
+
+#ifdef QET_CRASH_BACKTRACE
+		// Then where it was when it died. Last, deliberately: see the
+		// note above about the loader lock. backtrace() is warmed in
+		// install() so its first-call lazy resolution cannot allocate
+		// here, and backtrace_symbols_fd() writes to the fd without
+		// allocating -- unlike backtrace_symbols(), which mallocs and
+		// must not be used.
+		const char kBacktraceLabel[] = "--- backtrace ---\n";
+		::write(fd, kBacktraceLabel, sizeof(kBacktraceLabel) - 1);
+		const int frames = ::backtrace(g_backtrace_frames,
+					       static_cast<int>(sizeof(g_backtrace_frames)
+								/ sizeof(g_backtrace_frames[0])));
+		if (frames > 0) {
+			::backtrace_symbols_fd(g_backtrace_frames, frames, fd);
+		}
+#endif
+
 		::close(fd);
 	}
 
@@ -134,6 +196,34 @@ LONG WINAPI windowsExceptionFilter(EXCEPTION_POINTERS *)
 
 } // namespace
 
+// Async-signal-safe decimal formatting: write() takes a buffer, and there
+// is no snprintf on the POSIX async-signal-safe list. Writes into a
+// caller-owned buffer (stack, not heap) and returns the length used.
+//
+// Defined as CrashHandler::formatInt rather than a file-local helper only
+// so tst_crashhandler can reach it; it is not called anywhere else.
+int CrashHandler::formatInt(char *buffer, int size, int value)
+{
+	if (size <= 0) return 0;
+	if (value == 0) {
+		buffer[0] = '0';
+		return 1;
+	}
+	char scratch[16];
+	int n = 0;
+	bool negative = value < 0;
+	unsigned int v = negative ? static_cast<unsigned int>(-(value + 1)) + 1u
+				  : static_cast<unsigned int>(value);
+	while (v > 0 && n < static_cast<int>(sizeof(scratch))) {
+		scratch[n++] = static_cast<char>('0' + (v % 10));
+		v /= 10;
+	}
+	int len = 0;
+	if (negative && len < size) buffer[len++] = '-';
+	while (n > 0 && len < size) buffer[len++] = scratch[--n];
+	return len;
+}
+
 void CrashHandler::install(const LogRing *ring, const QString &dump_path)
 {
 	g_ring = ring;
@@ -159,6 +249,15 @@ void CrashHandler::install(const LogRing *ring, const QString &dump_path)
 	ss.ss_flags = 0;
 	sigaltstack(&ss, nullptr);
 
+#ifdef QET_CRASH_BACKTRACE
+	// Warm the unwinder. backtrace()'s *first* call resolves dynamic
+	// linker state and may allocate; every call after that does not. Doing
+	// it here, in normal context, is what lets the handler call it without
+	// breaking invariant 2. The result is deliberately discarded.
+	void *warmup[4];
+	(void) ::backtrace(warmup, 4);
+#endif
+
 	struct sigaction sa {};
 	sa.sa_handler = signalHandler;
 	sigemptyset(&sa.sa_mask);

sources/logging/crashhandler.h

@@ -33,11 +33,15 @@ class LogRing;
 	discussion's own words: "lands last, behind its own switch"), so its
 	invariants are worth restating plainly:
 
-	1. The handler must never block. It takes no locks -- LogRing itself
-	   is lock-free for exactly this reason (see logring.h). A handler
-	   that can hang is worse than no handler: it turns a clean crash
-	   (which at least produces a core dump) into a hung process that has
-	   to be force-killed, producing neither a core dump nor a ring dump.
+	1. The handler must never block. It takes no locks of its own --
+	   LogRing is lock-free for exactly this reason (see logring.h). A
+	   handler that can hang is worse than no handler: it turns a clean
+	   crash (which at least produces a core dump) into a hung process
+	   that has to be force-killed, producing neither a core dump nor a
+	   ring dump. The one exception is deliberate and comes last:
+	   backtrace() unwinds through libgcc, which takes the loader lock,
+	   so it is written after the ring rather than before it. A crash
+	   inside dlopen() then costs the backtrace, not the whole dump.
 	2. The handler must never allocate. Under heap corruption -- a
 	   plausible *cause* of the very crash being handled -- malloc may
 	   itself deadlock or fault. Every buffer this code touches at crash
@@ -78,6 +82,19 @@ class CrashHandler
 		/// touches QString.
 		static void install(const LogRing *ring, const QString &dump_path);
 
+			/// Writes `value` as decimal into `buffer`, at most `size`
+			/// bytes, and returns how many were written. The handler
+			/// needs this because write() takes a buffer and snprintf()
+			/// is not on the async-signal-safe list; `buffer` is caller-
+			/// owned (the handler's stack), so nothing is allocated.
+			/// Truncates rather than overflowing when `size` is too
+			/// small, and writes nothing for `size <= 0`.
+			///
+			/// Public only so tests can reach it -- see
+			/// tests/qttest/tst_crashhandler.cpp. Nothing else in the
+			/// application calls it.
+		static int formatInt(char *buffer, int size, int value);
+
 	private:
 		CrashHandler() = delete;
 };

sources/logging/qetlogger.cpp

@@ -21,10 +21,12 @@
 #include "../qetapp.h"
 #include "../qetversion.h"
 
+#include <QCoreApplication>
 #include <QDateTime>
 #include <QDir>
 #include <QFileInfo>
 #include <QSysInfo>
+#include <cctype>
 #include <cstdio>
 
 namespace {
@@ -104,12 +106,166 @@ void QetLogger::installCrashHandler()
 	if (m_disabled) {
 		return;
 	}
-	CrashHandler::install(&m_ring, crashDumpPath());
+		//Both run here, in normal startup context, before this run's own
+		//dump path is fixed: a dump left by a pre-#905 version is moved
+		//in so it can still be offered, and any backlog is trimmed.
+	migrateLegacyCrashDump();
+	pruneCrashDumps();
+
+		//Fixed for the life of the process: the handler copies it into a
+		//preallocated buffer, and pendingCrashDumpFiles() needs to know
+		//which file is this run's own so it doesn't offer it back.
+	m_crash_dump_path = buildCrashDumpPath();
+	CrashHandler::install(&m_ring, m_crash_dump_path);
 }
 
-QString QetLogger::crashDumpPath() const
+/**
+	@brief QetLogger::crashDumpDir
+	@return the directory holding crash dumps.
+
+	A directory rather than a single file, because dumps are per-run and
+	several can be waiting at once. Creates nothing: a getter that made a
+	directory as a side effect surprised a reviewer on #905, and the
+	readers here (listing, pruning) have no business creating it.
+*/
+QString QetLogger::crashDumpDir() const
 {
-	return m_log_dir % QStringLiteral("/crash_dump.log");
+	return m_log_dir % QStringLiteral("/crashes");
+}
+
+/**
+	@brief QetLogger::ensureCrashDumpDir
+	@return crashDumpDir(), created if missing.
+
+	For the callers that are about to write into it.
+*/
+QString QetLogger::ensureCrashDumpDir() const
+{
+	const QString dir = crashDumpDir();
+	QDir().mkpath(dir);
+	return dir;
+}
+
+/**
+	@brief QetLogger::migrateLegacyCrashDump
+
+	Before #905 the handler wrote to a single m_log_dir/crash_dump.log.
+	After upgrading, nothing looks at that path any more: the dump of the
+	crash that quite possibly prompted the upgrade would sit there unseen
+	and undeleted forever. Move it into crashes/ under a name the
+	crash_*.log filter matches, so it is offered exactly once like any
+	other. Named from its own mtime, so it sorts by when it was written
+	rather than when it was moved.
+*/
+void QetLogger::migrateLegacyCrashDump() const
+{
+	const QFileInfo legacy(m_log_dir % QStringLiteral("/crash_dump.log"));
+	if (!legacy.exists() || !legacy.isFile() || legacy.size() <= 0) {
+		return;
+	}
+
+	const QString target = ensureCrashDumpDir()
+		% QStringLiteral("/crash_")
+		% legacy.lastModified().toString(QStringLiteral("yyyyMMdd-hhmmss"))
+		% QStringLiteral("_legacy.log");
+
+	if (QFile::exists(target)) {
+			//Migrated already by an earlier run of this version.
+		QFile::remove(legacy.absoluteFilePath());
+		return;
+	}
+	QFile::rename(legacy.absoluteFilePath(), target);
+}
+
+/**
+	@brief QetLogger::pruneCrashDumps
+
+	A crash that repeats on startup would otherwise write one dump per
+	attempt without limit, since nothing is deleted until a dialog is
+	actually shown and answered. Keep the newest kMaxPendingCrashDumps --
+	enough to see a pattern, bounded however long the loop runs.
+*/
+void QetLogger::pruneCrashDumps() const
+{
+	QDir dir(crashDumpDir());
+	if (!dir.exists()) {
+		return;
+	}
+	dir.setNameFilters({QStringLiteral("crash_*.log")});
+	dir.setFilter(QDir::Files);
+	dir.setSorting(QDir::Time);
+
+	const QFileInfoList entries = dir.entryInfoList();
+	for (int i = kMaxPendingCrashDumps ; i < entries.size() ; ++i) {
+		QFile::remove(entries.at(i).absoluteFilePath());
+	}
+}
+
+/**
+	@brief QetLogger::buildCrashDumpPath
+	@return where this run would write a crash dump.
+
+	One file per run, rather than a single fixed crash_dump.log. That old
+	scheme opened one path with O_TRUNC, so a second crash overwrote the
+	first: someone who crashed ten times still ended up with exactly one
+	dump, the most recent. Reported on #898 -- "the report appeared only
+	once despite there being 10 or more crashes" -- where losing the
+	earlier dumps mattered as much as never being shown them.
+
+	Built here in normal context and handed to CrashHandler::install(),
+	which copies it into a preallocated buffer, so the handler still
+	writes to one fixed path and its no-allocation invariant is untouched.
+*/
+QString QetLogger::buildCrashDumpPath() const
+{
+	return ensureCrashDumpDir()
+		% QStringLiteral("/crash_")
+		% QDateTime::currentDateTime().toString(QStringLiteral("yyyyMMdd-hhmmss"))
+		% QStringLiteral("_")
+		% QString::number(QCoreApplication::applicationPid())
+		% QStringLiteral(".log");
+}
+
+/**
+	@brief QetLogger::pendingCrashDumpFiles
+	@return dumps left by previous runs, newest first, at most
+	kMaxPendingCrashDumps of them.
+
+	This run's own path is excluded: it does not exist yet unless this run
+	is itself crashing, and a handler mid-crash is in no position to be
+	offered a dialog.
+
+	Callers take this list once and pass it on to
+	pendingCrashDumpContents() and clearPendingCrashDump(), rather than
+	each of those re-reading the directory. See clearPendingCrashDump().
+*/
+QStringList QetLogger::pendingCrashDumpFiles() const
+{
+	QDir dir(crashDumpDir());
+	if (!dir.exists()) {
+		return QStringList();
+	}
+	dir.setNameFilters({QStringLiteral("crash_*.log")});
+	dir.setFilter(QDir::Files);
+	dir.setSorting(QDir::Time);
+
+	QStringList files;
+	const QFileInfoList entries = dir.entryInfoList();
+	for (const QFileInfo &info : entries)
+	{
+		if (info.size() <= 0) {
+			continue;
+		}
+		if (!m_crash_dump_path.isEmpty()
+				&& info.absoluteFilePath() == QFileInfo(m_crash_dump_path).absoluteFilePath()) {
+			continue;
+		}
+		files << info.absoluteFilePath();
+		if (files.size() >= kMaxPendingCrashDumps) {
+			break;
+		}
+	}
+	return files;
 }
 
 QString QetLogger::currentLogFilePath() const
@@ -362,22 +518,67 @@ bool QetLogger::hasPendingCrashDump() const
 	if (m_disabled) {
 		return false;
 	}
-	const QFileInfo info(crashDumpPath());
-	return info.exists() && info.isFile() && info.size() > 0;
+	return !pendingCrashDumpFiles().isEmpty();
 }
 
-QByteArray QetLogger::pendingCrashDumpContents() const
+/**
+	@brief QetLogger::pendingCrashDumpContents
+	@param files the list from pendingCrashDumpFiles()
+	@return those dumps, in the order given, concatenated.
+
+	All of them rather than only the latest: a crash that repeats is the
+	case where the earlier dumps are most worth having, since the
+	difference between them is the evidence. They are separated by a
+	banner so a reader can tell where one ends and the next begins, and
+	the whole thing is redacted as a single pass.
+*/
+QByteArray QetLogger::pendingCrashDumpContents(const QStringList &files) const
 {
-	QFile file(crashDumpPath());
-	if (!file.open(QIODevice::ReadOnly)) {
+	if (files.isEmpty()) {
 		return QByteArray();
 	}
-	return redact(file.readAll());
+
+	QByteArray all;
+	if (files.size() > 1) {
+		all += QByteArray("QET: ") + QByteArray::number(files.size())
+			+ " crash dumps pending, newest first.\n\n";
+	}
+
+	for (const QString &path : files)
+	{
+		QFile file(path);
+		if (!file.open(QIODevice::ReadOnly)) {
+			continue;
+		}
+		all += "===== " + QFileInfo(path).fileName().toUtf8() + " =====\n";
+		all += file.readAll();
+		if (!all.endsWith('\n')) {
+			all += '\n';
+		}
+		all += '\n';
+	}
+
+	return redact(all);
 }
 
-void QetLogger::clearPendingCrashDump()
+/**
+	@brief QetLogger::clearPendingCrashDump
+	@param files exactly the dumps that were offered
+
+	Deletes the list it is given rather than re-reading the directory.
+	The offer sits inside a modal dialog that can stay open for as long
+	as the user cares to read it, and dumps are per-run: a second
+	QElectroTech -- SingleApplication keys its socket on the binary path,
+	so a different build is a separate instance -- can crash and write a
+	new dump while that dialog is up. Re-listing at this point would
+	delete that fresh dump without anyone ever having seen it, which is
+	the failure this whole change is about.
+*/
+void QetLogger::clearPendingCrashDump(const QStringList &files)
 {
-	QFile::remove(crashDumpPath());
+	for (const QString &path : files) {
+		QFile::remove(path);
+	}
 }
 
 QByteArray QetLogger::buildDiagnosticsReport() const
@@ -421,11 +622,30 @@ QByteArray QetLogger::buildDiagnosticsReport() const
 */
 QByteArray QetLogger::redact(const QByteArray &input)
 {
-	const QByteArray home = QDir::homePath().toUtf8();
-	if (home.isEmpty()) {
-		return input;
-	}
 	QByteArray out = input;
-	out.replace(home, QByteArrayLiteral("~"));
+
+	const QByteArray home = QDir::homePath().toUtf8();
+	if (!home.isEmpty()) {
+		out.replace(home, QByteArrayLiteral("~"));
+	}
+
+		//backtrace_symbols_fd() writes the absolute path of each module,
+		//which for an AppImage is the per-run mount point
+		///tmp/.mount_QElectXXXXXX. Not identifying on its own, but it is
+		//noise in a bug report and it is a path the user never typed, so
+		//fold it to a stable name. Done after the home replacement above
+		//because the mount point is not under $HOME.
+	const QByteArray mount_prefix("/tmp/.mount_");
+	int at = out.indexOf(mount_prefix);
+	while (at >= 0)
+	{
+		int end = at + mount_prefix.size();
+		while (end < out.size() && out.at(end) != '/' && !isspace(static_cast<unsigned char>(out.at(end)))) {
+			++end;
+		}
+		out.replace(at, end - at, QByteArrayLiteral("<appimage>"));
+		at = out.indexOf(mount_prefix, at + 10);
+	}
+
 	return out;
 }

sources/logging/qetlogger.h

@@ -76,6 +76,7 @@ class QetLogger
 		static constexpr qint64 kMaxFileBytes = 2 * 1024 * 1024; // 2 MiB per file
 		static constexpr int kRotationKeep = 4;                  // .1.log .. .4.log
 		static constexpr int kMaxMessageBytes = 4096;             // per-message truncation
+		static constexpr int kMaxPendingCrashDumps = 10;          // newest kept, rest pruned
 
 		static QetLogger &instance();
 
@@ -106,15 +107,24 @@ class QetLogger
 		/// dump behind.
 		bool hasPendingCrashDump() const;
 
-		/// Raw contents of the pending crash dump, or an empty array if
-		/// there isn't one. Does not delete it -- call
-		/// clearPendingCrashDump() once it has been offered to the user.
-		QByteArray pendingCrashDumpContents() const;
+		/// Dumps left by previous runs, newest first, capped at
+		/// kMaxPendingCrashDumps. This run's own dump path is never
+		/// included. Take this list once and pass the same list to
+		/// pendingCrashDumpContents() and clearPendingCrashDump(): that
+		/// is what makes "only what was offered gets deleted" true,
+		/// rather than re-reading the directory at each step and
+		/// deleting a dump that arrived in between unseen.
+		QStringList pendingCrashDumpFiles() const;
 
-		/// Deletes the pending crash dump file. Call after the user has
-		/// been offered it (whether they chose to save it or not) so it
-		/// is never offered a second time.
-		void clearPendingCrashDump();
+		/// Raw contents of `files`, newest first, concatenated and
+		/// redacted. Deletes nothing -- pass the same list to
+		/// clearPendingCrashDump() once it has been offered.
+		QByteArray pendingCrashDumpContents(const QStringList &files) const;
+
+		/// Deletes exactly `files`, nothing else. Call after the user
+		/// has been offered them (whether they chose to save them or
+		/// not) so they are never offered a second time.
+		void clearPendingCrashDump(const QStringList &files);
 
 		/// Builds a redacted diagnostics bundle from the *current* session
 		/// (header + this session's log file so far) for the manual
@@ -122,10 +132,13 @@ class QetLogger
 		/// which is about a *previous*, already-terminated session.
 		QByteArray buildDiagnosticsReport() const;
 
-		/// Replaces occurrences of the user's home directory with "~".
-		/// Applied to both the crash dump and buildDiagnosticsReport()
-		/// before they are ever shown to the user, since both are
-		/// destined for a public bug tracker.
+		/// Replaces occurrences of the user's home directory with "~",
+		/// and an AppImage's per-run /tmp/.mount_XXXXXX prefix with
+		/// "<appimage>" -- the latter because backtrace_symbols_fd()
+		/// writes absolute module paths into the dump. Applied to both
+		/// the crash dump and buildDiagnosticsReport() before they are
+		/// ever shown to the user, since both are destined for a public
+		/// bug tracker.
 		static QByteArray redact(const QByteArray &input);
 
 	private:
@@ -136,7 +149,18 @@ class QetLogger
 		void rotateLocked();
 		void writeToFile(const QByteArray &line, QtMsgType type);
 		QString rotatedPath(int index) const;
-		QString crashDumpPath() const;
+			/// Pure path getter: creates nothing. Callers that are about
+			/// to write there call ensureCrashDumpDir() instead.
+		QString crashDumpDir() const;
+		QString ensureCrashDumpDir() const;
+		QString buildCrashDumpPath() const;
+			/// Moves a crash_dump.log left by a pre-#905 version into
+			/// crashes/, so upgrading does not strand it unoffered.
+		void migrateLegacyCrashDump() const;
+			/// Keeps the newest kMaxPendingCrashDumps dumps and deletes
+			/// the rest, so a crash loop cannot fill the log directory
+			/// before anyone gets the chance to see a dialog.
+		void pruneCrashDumps() const;
 		QString currentLogFilePath() const;
 
 		static QByteArray sanitize(const QByteArray &input);
@@ -147,6 +171,10 @@ class QetLogger
 
 		QString m_log_dir;
 		QString m_base_name; // e.g. "20260803", resolved once in init()
+			/// This run's own dump path, fixed at installCrashHandler():
+			/// the handler writes here, and it is excluded when collecting
+			/// dumps left by previous runs.
+		QString m_crash_dump_path;
 
 		QMutex m_file_mutex;
 		QFile m_file;

sources/print/projectprintwindow.cpp

@@ -56,7 +56,6 @@
 void ProjectPrintWindow::launchDialog(QETProject *project, QPrinter::OutputFormat format, QWidget *parent)
 {
 	auto printer_ = new QPrinter();
-	QPrinter printer(QPrinter::HighResolution);
 	printer_->setDocName(ProjectPrintWindow::docName(project));
 	printer_->setPageOrientation(QPageLayout::Landscape);
 
@@ -150,6 +149,11 @@ ProjectPrintWindow::ProjectPrintWindow(QETProject *project, QPrinter *printer, Q
 	ui->m_draw_terminal_names_cb->setChecked(exp.draw_terminal_names);
 	ui->m_keep_conductor_color_cb->setChecked(exp.draw_colored_conductors);
 
+	QSettings settings;
+	ui->m_component_info_cb->setChecked(settings.value("print/default/componentinfo", false).toBool());
+	ui->m_fit_in_page_cb->setChecked(settings.value("print/default/fitinpage", true).toBool());
+	ui->m_use_full_page_cb->setChecked(settings.value("print/default/fullpage", false).toBool());
+
 	ui->m_date_cb->blockSignals(true);
 	ui->m_date_cb->setDate(QDate::currentDate());
 	ui->m_date_cb->blockSignals(false);
@@ -657,6 +661,16 @@ void ProjectPrintWindow::loadPageSetupForCurrentPrinter()
 	settings.endGroup();
 }
 
+void ProjectPrintWindow::savePrintProperties()
+{
+	QSettings settings;
+	exportProperties().toSettings(settings, "print/default");
+	settings.setValue("print/default/componentinfo", ui->m_component_info_cb->isChecked());
+	settings.setValue("print/default/fitinpage", ui->m_fit_in_page_cb->isChecked());
+	settings.setValue("print/default/fullpage", ui->m_use_full_page_cb->isChecked());
+	settings.sync();
+}
+
 void ProjectPrintWindow::savePageSetupForCurrentPrinter()
 {
 	QSettings settings;
@@ -842,6 +856,7 @@ void ProjectPrintWindow::print()
 	                      // is created/destroyed inside that call
 
 	savePageSetupForCurrentPrinter();
+	savePrintProperties();
 
 	if (isPdf && !pdfFile.isEmpty()) {
 		// Defer post-processing and window close to the next event-loop

sources/print/projectprintwindow.h

@@ -91,6 +91,7 @@ class ProjectPrintWindow : public QMainWindow
 		void setUpDiagramList();
 		QString settingsSectionName(const QPrinter *printer);
 		void loadPageSetupForCurrentPrinter();
+		void savePrintProperties();
 		void savePageSetupForCurrentPrinter();
 		void saveReloadDiagramParameters(Diagram *diagram, const ExportProperties &options, bool save);
 		QList<Diagram *> selectedDiagram() const;

sources/qetapp.cpp

@@ -2759,11 +2759,16 @@ void QETApp::offerBackupFiles(const QList<KAutoSaveFile *> &stale_files)
 void QETApp::checkCrashDump()
 {
 	QetLogger &logger = QetLogger::instance();
-	if (!logger.hasPendingCrashDump()) {
+
+	// Listed once, then used both to build the contents and to delete
+	// below. Re-listing after the dialog closes would delete a dump
+	// written while it was open, unseen -- see clearPendingCrashDump().
+	const QStringList offered = logger.pendingCrashDumpFiles();
+	if (offered.isEmpty()) {
 		return;
 	}
 
-	const QByteArray content = logger.pendingCrashDumpContents();
+	const QByteArray content = logger.pendingCrashDumpContents(offered);
 
 	DiagnosticsReportDialog dialog(
 			tr("Rapport de plantage"),
@@ -2775,7 +2780,7 @@ void QETApp::checkCrashDump()
 
 	// Offered once, then marked retrieved -- regardless of whether the
 	// user chose to save it -- so it is never offered a second time.
-	logger.clearPendingCrashDump();
+	logger.clearPendingCrashDump(offered);
 }
 
 /**

sources/qetmainwindow.cpp

@@ -16,6 +16,7 @@
 	along with QElectroTech.  If not, see <http://www.gnu.org/licenses/>.
 */
 #include <QAction>
+#include <QApplication>
 #include <QWhatsThis>
 #include <QMenu>
 #include <QMenuBar>
@@ -290,6 +291,9 @@ void QETMainWindow::activateMenuBar() {
 }
 
 bool QETMainWindow::event(QEvent *e) {
+	if (e -> type() == QEvent::Close && refuseCloseWhileModal(e)) {
+		return(true);
+	}
 	if (e -> type() == QEvent::WindowStateChange) {
 		updateFullScreenAction();
 	} else if (first_activation_ && e -> type() == QEvent::WindowActivate) {
@@ -299,6 +303,44 @@ bool QETMainWindow::event(QEvent *e) {
 	return(QMainWindow::event(e));
 }
 
+/**
+	@brief QETMainWindow::refuseCloseWhileModal
+	Refuse to close an editor window while any modal dialog is running.
+
+	A modal dialog's exec() runs a nested event loop. If a window is closed
+	during it, the window's WA_DeleteOnClose turns into a deleteLater() that
+	the *nested* loop processes: the window is destroyed while code that
+	belongs to it -- often the very function that opened the dialog -- is
+	still on the stack. Most of QET's dialogs are stack objects parented to
+	the window (BackupDialog, and every QET::QetMessageBox), so ~QWidget()
+	then deletes a stack object and the process aborts (issue #904). Even a
+	dialog without a parent would only trade that abort for a silent
+	use-after-free in the caller.
+
+	Qt already ignores window-manager close requests for a window blocked by
+	a modal, so this is only reachable through close() called directly: the
+	File > Quit action, which macOS moves into the application menu where it
+	stays usable during a modal, and QETApp::quitQET() from the system tray.
+
+	Handled in event(), before closeEvent() runs, because the editors'
+	closeEvent() starts closing projects before it decides whether to accept.
+	The dialog is raised so a refused quit is not silent.
+
+	@param e : the QEvent::Close being delivered
+	@return true if the close was refused and must not be processed further
+*/
+bool QETMainWindow::refuseCloseWhileModal(QEvent *e)
+{
+	QWidget *modal = QApplication::activeModalWidget();
+	if (!modal) {
+		return(false);
+	}
+	modal -> raise();
+	modal -> activateWindow();
+	e -> ignore();
+	return(true);
+}
+
 /**
 	Base implementation of firstActivation (does nothing).
 */

sources/qetmainwindow.h

@@ -31,6 +31,8 @@ class QETMainWindow : public QMainWindow {
 	QETMainWindow(QWidget * = nullptr, Qt::WindowFlags = Qt::Widget);
 	~QETMainWindow() override;
 
+	static bool refuseCloseWhileModal(QEvent *e);
+	
 	// methods
 	protected:
 	void initCommonActions();

tests/CMakeLists.txt

@@ -29,5 +29,7 @@ message(". Add sub directory googletest")
 add_subdirectory(googletest)
 message(". Add sub directory googlemock")
 add_subdirectory(googlemock)
+message(". Add sub directory modal-quit-regression")
+add_subdirectory(modal-quit-regression)
 message(". Add sub directory qttest")
 add_subdirectory(qttest)

tests/modal-quit-regression/CMakeLists.txt

@@ -0,0 +1,30 @@
+# Copyright 2006 The QElectroTech Team
+# This file is part of QElectroTech.
+#
+# QElectroTech is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#
+# QElectroTech is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with QElectroTech. If not, see <http://www.gnu.org/licenses/>.
+
+# Issue #904 -- see run.sh for what this guards and how.
+#
+# Driven by gdb, so it is registered on Linux only. It reports 77 (SKIP)
+# rather than failing when it cannot run at all: no gdb, a gdb without
+# Python, or a stripped binary whose symbols it cannot call.
+if(UNIX AND NOT APPLE)
+  message(". Add test modal_quit_regression")
+  add_test(
+    NAME modal_quit_regression
+    COMMAND ${CMAKE_CURRENT_SOURCE_DIR}/run.sh --binary $<TARGET_FILE:qelectrotech>)
+  set_tests_properties(modal_quit_regression PROPERTIES
+    SKIP_RETURN_CODE 77
+    TIMEOUT 180)
+endif()

tests/modal-quit-regression/README.md

@@ -0,0 +1,71 @@
+# Quit-during-modal regression test
+
+Guards the abort reported in #904.
+
+`QETDiagramEditor::openAndAddProject()` shows `BackupDialog` as a stack object
+parented to the editor and `exec()`s it, and `QET::QetMessageBox` does the same
+for every message box. `exec()` runs a nested event loop. Closing the editor
+during that loop turns `WA_DeleteOnClose` into a `deleteLater()` that the nested
+loop processes, so `~QWidget()` deletes the stack-allocated dialog and the
+process aborts. `QETMainWindow::refuseCloseWhileModal()` refuses such a close.
+
+## Running it
+
+```bash
+tests/modal-quit-regression/run.sh --binary build/qelectrotech
+```
+
+Needs `gdb` with Python. It runs on the offscreen platform, so no X server or
+window manager is required. Takes about ten seconds.
+
+It is also registered with CTest on Linux (`ctest -R modal_quit_regression`).
+
+Exit codes: `0` survived, `1` crashed, `2` the scenario did not happen,
+`77` it could not run here.
+
+That last one matters for a release build. The scenario is driven by calling
+`QETApp::instance()` and `QETApp::quitQET()` through gdb, so those symbols have
+to survive into the binary: against a **stripped** build there is nothing to
+call, and the same applies without gdb or with a gdb built without Python. All
+three report 77, which is CTest's `SKIP_RETURN_CODE`, so a build this test
+cannot drive is skipped rather than failed.
+
+## How it works, and why this way
+
+On Linux there is nothing to click: the menu bar belongs to the window the
+dialog blocks, and Qt ignores window-manager close requests for a blocked
+window. The reported route is macOS, where File > Quit lives in the application
+menu and stays usable during a modal — and what it does is call `close()` while
+the dialog's loop is running. The test does the same thing through gdb:
+
+1. break on `QDialog::exec()`;
+2. let the dialog's loop run, then interrupt it, so the main thread is inside
+   the nested loop — the only place the bug exists, because a `deleteLater()`
+   posted *before* `exec()` started is not processed by that loop;
+3. call `QETApp::quitQET()`, which closes every editor;
+4. let it run: an unfixed build aborts within a second.
+
+It matches no window titles and no window ids. Titles are translated, and
+`tests/ipc-regression` once shipped a pass that could not fail because of that.
+
+## Covering the element editor too
+
+`--project` decides which editor is under test, because QElectroTech picks the
+editor from the file extension. Pass a `.qet` and the run exercises
+`QETDiagramEditor`; pass a **read-only `.elmt`** and it exercises
+`QETElementEditor`, which shows a "file is read-only" message box on open and so
+reaches the same nested loop by a different route:
+
+```bash
+chmod -w some.elmt
+tests/modal-quit-regression/run.sh --binary build/qelectrotech --project some.elmt
+```
+
+That distinction is why the file name is preserved when it is copied into the
+sandbox. Renaming a `.elmt` to `project.qet` would make the run silently test
+the diagram editor again, and still report PASS.
+
+Checked both ways, in both editors, before being committed: without the fix the
+diagram-editor run aborts with signal 6 under `~QETDiagramEditor()` and the
+element-editor run with `double free or corruption` under
+`~QETElementEditor()`; with the fix both survive.

tests/modal-quit-regression/run.sh

@@ -0,0 +1,197 @@
+#!/usr/bin/env bash
+#
+# Quit-during-modal regression gate -- issue #904.
+#
+#   tests/modal-quit-regression/run.sh --binary build/qelectrotech
+#   tests/modal-quit-regression/run.sh --binary build/qelectrotech \
+#                                      --project read-only.elmt
+#
+# --project also picks the editor under test: QElectroTech chooses it from the
+# extension, so a .qet exercises QETDiagramEditor and a read-only .elmt
+# exercises QETElementEditor (which opens a message box of its own).
+#
+# WHAT IT GUARDS
+#
+# QETDiagramEditor::openAndAddProject() shows BackupDialog as a stack object
+# parented to the editor and exec()s it; QET::QetMessageBox does the same for
+# every message box. exec() runs a NESTED event loop. If the editor is closed
+# during that loop, WA_DeleteOnClose becomes a deleteLater() that the nested
+# loop processes: ~QWidget() deletes the editor's children, the stack-allocated
+# dialog among them, and the process aborts ("free(): invalid size").
+# QETMainWindow::refuseCloseWhileModal() refuses such a close.
+#
+# HOW IT TRIGGERS THE BUG WITHOUT A MOUSE
+#
+# On Linux the menu bar belongs to the window the modal blocks, and Qt ignores
+# window-manager close requests for a blocked window, so there is nothing to
+# click. The reported route is macOS, where File > Quit moves to the
+# application menu and stays usable. What that route does is call close()
+# programmatically while the dialog's loop is spinning, and that is what this
+# test does, through gdb:
+#
+#   1. break on QDialog::exec(), i.e. the moment the first dialog is shown;
+#   2. let it run for a moment, then interrupt it -- the main thread is now
+#      inside the dialog's nested loop, which is the only place the bug lives
+#      (a deleteLater() posted before exec() started is not processed by it);
+#   3. call QETApp::quitQET(), which closes every editor;
+#   4. let it run again: the unfixed build aborts within a second, the fixed
+#      one keeps running until the test interrupts it.
+#
+# Nothing here matches a window title or a window id. A title is a locale:
+# tests/ipc-regression once shipped a pass that could not fail because the
+# dialog it filtered by name was translated differently in Docker.
+#
+# It runs on the offscreen platform, so no X server or window manager is
+# needed -- only gdb with Python.
+#
+# RESULT
+#   exit 0   PASS   quitQET() ran inside the modal loop and the process survived
+#   exit 1   FAIL   the process died of a signal after quitQET()
+#   exit 2   ERROR  the scenario never happened (no dialog, gdb problem, ...)
+#   exit 77  SKIP   cannot run here: no gdb, a gdb without Python, or a
+#                   stripped binary. 77 is CTest's SKIP_RETURN_CODE, so a
+#                   build this test cannot drive is reported as skipped
+#                   rather than failed.
+#
+set -uo pipefail
+
+BINARY=""
+PROJECT=""
+SETTLE=2      # seconds inside the dialog loop before interrupting
+OBSERVE=5     # seconds to wait for a crash after quitQET()
+
+while [ $# -gt 0 ]; do
+    case "$1" in
+        --binary)  BINARY="$2"; shift 2 ;;
+        --project) PROJECT="$2"; shift 2 ;;
+        *) echo "unknown argument: $1" >&2; exit 2 ;;
+    esac
+done
+
+[ -n "$BINARY" ] || { echo "usage: $0 --binary <qet> [--project <file.qet>]" >&2; exit 2; }
+[ -x "$BINARY" ] || { echo "not executable: $BINARY" >&2; exit 2; }
+BINARY="$(readlink -f "$BINARY")"
+
+if [ -z "$PROJECT" ]; then
+    SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+    PROJECT="$(ls "$SCRIPT_DIR"/../../examples/*.qet 2>/dev/null | head -1)"
+fi
+[ -f "$PROJECT" ] || { echo "no project found; pass --project" >&2; exit 2; }
+
+skip() { echo "SKIP: $1"; exit 77; }
+
+command -v gdb >/dev/null || skip "gdb is not installed"
+gdb -batch -ex 'python import gdb' >/dev/null 2>&1 \
+    || skip "this gdb has no Python support"
+
+# The scenario is driven by calling QETApp::instance() and QETApp::quitQET()
+# through gdb, so their symbols have to survive into the binary. A stripped
+# release build cannot be driven at all -- that is a property of the build,
+# not a failure of the code under test, so report it as skipped.
+#
+# Read nm's output once into a variable rather than piping it into grep -q:
+# grep -q exits at the first match, nm dies of SIGPIPE, and under `set -o
+# pipefail` the pipeline reports failure even though the symbol was found --
+# which would skip this test on every build that can actually run it.
+if command -v nm >/dev/null; then
+    SYMBOLS="$(nm -C "$BINARY" 2>/dev/null || true)"
+    for sym in "QETApp::instance()" "QETApp::quitQET()"; do
+        case "$SYMBOLS" in
+            *"$sym"*) ;;
+            *) skip "binary has no symbol for $sym (stripped build?)" ;;
+        esac
+    done
+fi
+
+SANDBOX="$(mktemp -d /tmp/qet-modal-quit.XXXXXX)"
+cleanup() { [ "${KEEP_LOGS:-0}" = "1" ] || rm -rf "$SANDBOX"; }
+trap cleanup EXIT
+
+# A unique binary path gives this run its own SingleApplication socket, so it
+# can neither be captured by nor capture a QElectroTech already running. A
+# symlink would not do: applicationFilePath() resolves it back to the real path.
+TEST_BINARY="$SANDBOX/qelectrotech-modalquit"
+cp "$BINARY" "$TEST_BINARY" || { echo "could not copy binary" >&2; exit 2; }
+
+# Keep the original file name. QElectroTech decides what to open from the
+# extension, so copying a .elmt to "project.qet" would quietly turn an
+# element-editor run into a failed project load -- and the scenario would
+# still "work", against the wrong window.
+SANDBOX_PROJECT="$SANDBOX/$(basename "$PROJECT")"
+cp "$PROJECT" "$SANDBOX_PROJECT" || { echo "could not copy input file" >&2; exit 2; }
+
+export HOME="$SANDBOX/home"
+export XDG_CONFIG_HOME="$HOME/.config"
+export XDG_DATA_HOME="$HOME/.local/share"
+mkdir -p "$XDG_CONFIG_HOME" "$XDG_DATA_HOME"
+export QT_QPA_PLATFORM=offscreen
+
+cat > "$SANDBOX/scenario.gdb" <<EOF
+set debuginfod enabled off
+set pagination off
+set confirm off
+set breakpoint pending on
+handle SIGINT stop print nopass
+python
+import subprocess
+def qet_interrupt_later(seconds):
+    pid = gdb.selected_inferior().pid
+    subprocess.Popen(["sh", "-c", "sleep %d; kill -INT %d" % (seconds, pid)])
+end
+break QDialog::exec
+run
+delete
+printf "QET_TEST: dialog exec() entered\n"
+python qet_interrupt_later($SETTLE)
+continue
+thread 1
+set \$app = ((void* (*)(void))'QETApp::instance()')()
+call ((void (*)(void*))'QETApp::quitQET()')(\$app)
+printf "QET_TEST: quitQET() returned\n"
+python qet_interrupt_later($OBSERVE)
+continue
+printf "QET_TEST: final signal %d\n", \$_siginfo.si_signo
+bt 20
+kill
+EOF
+
+# Bound the run with timeout(1) rather than a backgrounded watchdog subshell.
+# A "( sleep N; kill ) &" watchdog runs sleep as a child of the subshell, so
+# killing the subshell orphans the sleep -- and the orphan keeps this script's
+# stdout open. Read through a pipe, as CTest does, that makes every run last
+# the full watchdog period no matter how fast gdb finished: ten seconds of
+# work reported as two minutes, a stone's throw from the CTest timeout.
+GDB_TIMEOUT=120
+if command -v timeout >/dev/null; then
+    timeout --signal=KILL "$GDB_TIMEOUT" \
+        gdb -batch -x "$SANDBOX/scenario.gdb" --args "$TEST_BINARY" "$SANDBOX_PROJECT" \
+        > "$SANDBOX/gdb.log" 2>&1
+else
+    gdb -batch -x "$SANDBOX/scenario.gdb" --args "$TEST_BINARY" "$SANDBOX_PROJECT" \
+        > "$SANDBOX/gdb.log" 2>&1
+fi
+
+log="$SANDBOX/gdb.log"
+if ! grep -q "QET_TEST: dialog exec() entered" "$log"; then
+    echo "ERROR: no dialog was ever shown -- the scenario did not happen"
+    KEEP_LOGS=1; echo "log kept: $log"; exit 2
+fi
+if ! grep -q "QET_TEST: quitQET() returned" "$log"; then
+    echo "ERROR: quitQET() was not called inside the dialog loop"
+    KEEP_LOGS=1; echo "log kept: $log"; exit 2
+fi
+
+sig="$(sed -n 's/^QET_TEST: final signal \([0-9]*\)$/\1/p' "$log" | tail -1)"
+case "$sig" in
+    2)
+        echo "PASS: closing the editor during a modal dialog was refused; the process survived"
+        exit 0 ;;
+    "")
+        echo "ERROR: could not tell how the run ended"
+        KEEP_LOGS=1; echo "log kept: $log"; exit 2 ;;
+    *)
+        echo "FAIL: the process died of signal $sig after quitQET() ran inside the dialog loop (issue #904)"
+        grep -m1 -E "free\(\)|double free|corrupted" "$log" | sed 's/^/  /'
+        sed -n '/^QET_TEST: final signal/,$p' "$log" | grep -E '^#[0-9]+ ' | sed 's/^/  /'
+        KEEP_LOGS=1; echo "log kept: $log"; exit 1 ;;
+esac

tests/qttest/CMakeLists.txt

@@ -48,6 +48,18 @@ find_package(
  Test
  REQUIRED)
 
+# tst_crashhandler compiles crashhandler.cpp, which on a non-Windows build
+# may pull in backtrace(). Resolved the same way as in the top-level
+# CMakeLists so this directory also configures standalone -- on FreeBSD the
+# symbol lives in libexecinfo, not libc.
+if(NOT DEFINED Backtrace_FOUND)
+  find_package(Backtrace QUIET)
+  if(Backtrace_FOUND)
+    include_directories(${Backtrace_INCLUDE_DIRS})
+    add_compile_definitions(QET_CRASH_BACKTRACE)
+  endif()
+endif()
+
 include(../../cmake/fetch_kdeaddons.cmake)
 include(../../cmake/fetch_singleapplication.cmake)
 include(../../cmake/fetch_pugixml.cmake)
@@ -126,6 +138,41 @@ add_test(NAME tst_qetstrings COMMAND tst_qetstrings)
 target_include_directories(tst_qetstrings PRIVATE ${QET_DIR}/sources)
 target_link_libraries(tst_qetstrings PRIVATE Qt::Test Qt::Widgets Qt::Xml)
 
+# CrashHandler::formatInt() -- the async-signal-safe decimal formatter the
+# signal handler uses for the "Signal: N" line of a crash dump. Compiles
+# crashhandler.cpp and logring.cpp alongside; the handler deliberately
+# depends on nothing heavier than QByteArray.
+add_executable(
+  tst_crashhandler
+  tst_crashhandler.cpp
+  ${QET_DIR}/sources/logging/crashhandler.cpp
+  ${QET_DIR}/sources/logging/logring.cpp
+  ${QET_DIR}/sources/qetversion.cpp)
+add_test(NAME tst_crashhandler COMMAND tst_crashhandler)
+target_include_directories(tst_crashhandler PRIVATE ${QET_DIR}/sources)
+# Qt::Xml because crashhandler.cpp includes qetversion.h for the header it
+# builds at install() time, and that pulls in QDomElement.
+target_link_libraries(tst_crashhandler PRIVATE Qt::Test Qt::Xml ${Backtrace_LIBRARIES})
+
+# The crash-dump bookkeeping from #905: which dumps get listed, offered and
+# deleted, and what redact() masks. qetlogger.cpp needs exactly one symbol
+# from the application (QETApp::dataDir()), which the test supplies itself,
+# so this links the logging sources rather than the whole program.
+add_executable(
+  tst_crashdumps
+  tst_crashdumps.cpp
+  ${QET_DIR}/sources/logging/qetlogger.cpp
+  ${QET_DIR}/sources/logging/crashhandler.cpp
+  ${QET_DIR}/sources/logging/logring.cpp
+  ${QET_DIR}/sources/qetversion.cpp)
+add_test(NAME tst_crashdumps COMMAND tst_crashdumps)
+target_include_directories(tst_crashdumps PRIVATE
+  ${QET_DIR}
+  ${QET_DIR}/sources
+  ${QET_DIR}/sources/NameList
+  ${QET_DIR}/pugixml/src)
+target_link_libraries(tst_crashdumps PRIVATE Qt::Test Qt::Widgets Qt::Xml ${Backtrace_LIBRARIES})
+
 add_executable(
   tst_menubarkeyboard
   tst_menubarkeyboard.cpp)

tests/qttest/tst_crashdumps.cpp

@@ -0,0 +1,312 @@
+/*
+	Copyright 2006-2026 The QElectroTech Team
+	This file is part of QElectroTech.
+
+	QElectroTech is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 2 of the License, or
+	(at your option) any later version.
+
+	QElectroTech is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with QElectroTech.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "logging/qetlogger.h"
+
+#include "qetapp.h"
+
+#include <QDir>
+#include <QFile>
+#include <QTemporaryDir>
+#include <QTest>
+
+/**
+	QetLogger::init() asks QETApp for the data directory, and that is the
+	only thing it needs from the application. Standing in for it here is
+	what lets the crash-dump bookkeeping be tested without linking (or
+	starting) the whole of QElectroTech.
+*/
+namespace {
+	QString g_data_dir;
+}
+
+QString QETApp::dataDir()
+{
+	return g_data_dir;
+}
+
+/**
+	@brief The tst_CrashDumps class
+
+	Covers the crash-dump bookkeeping added in #905: one file per run
+	instead of a single crash_dump.log that each crash overwrote (#898),
+	and the rules about which of those files get offered and deleted.
+*/
+class tst_CrashDumps : public QObject
+{
+	Q_OBJECT
+
+	private slots:
+		void init();
+
+		void listsNothingWhenThereHasBeenNoCrash();
+		void listsDumpsNewestFirst();
+		void skipsEmptyDumps();
+		void excludesThisRunsOwnDump();
+		void capsTheListAtTenDumps();
+		void concatenatesEveryOfferedDump();
+		void clearsOnlyWhatWasOffered();
+
+		void redactsTheHomeDirectory();
+		void redactsAnAppImageMountPoint();
+		void redactsBothInOneString();
+
+	private:
+		QTemporaryDir m_dir;
+		QString crashesDir() const {return g_data_dir + QStringLiteral("/crashes");}
+		void writeDump(const QString &name, const QByteArray &body,
+			       const QDateTime &when = QDateTime());
+};
+
+void tst_CrashDumps::init()
+{
+	QVERIFY(m_dir.isValid());
+	// A fresh subdirectory per test: QetLogger is a singleton, so the
+	// tests share one instance and must not share its files.
+	static int n = 0;
+	g_data_dir = m_dir.path() + QStringLiteral("/run") + QString::number(++n);
+	QVERIFY(QDir().mkpath(g_data_dir));
+	QVERIFY(QDir().mkpath(crashesDir()));
+}
+
+void tst_CrashDumps::writeDump(const QString &name, const QByteArray &body,
+			       const QDateTime &when)
+{
+	const QString path = crashesDir() + QStringLiteral("/") + name;
+	{
+		QFile f(path);
+		QVERIFY(f.open(QIODevice::WriteOnly));
+		f.write(body);
+		f.close();
+	}
+	if (!when.isValid()) {
+		return;
+	}
+	// Separately, and only once the write is closed: setFileTime() needs
+	// an open handle, but closing a file that was just written sets the
+	// modification time to now, which would undo it.
+	QFile stamp(path);
+	QVERIFY(stamp.open(QIODevice::ReadWrite));
+	QVERIFY(stamp.setFileTime(when, QFileDevice::FileModificationTime));
+	stamp.close();
+}
+
+void tst_CrashDumps::listsNothingWhenThereHasBeenNoCrash()
+{
+	QetLogger::instance().init();
+	QVERIFY(QetLogger::instance().pendingCrashDumpFiles().isEmpty());
+	QVERIFY(!QetLogger::instance().hasPendingCrashDump());
+}
+
+void tst_CrashDumps::listsDumpsNewestFirst()
+{
+	const QDateTime base = QDateTime::currentDateTime();
+	writeDump(QStringLiteral("crash_a.log"), "oldest", base.addSecs(-300));
+	writeDump(QStringLiteral("crash_b.log"), "middle", base.addSecs(-200));
+	writeDump(QStringLiteral("crash_c.log"), "newest", base.addSecs(-100));
+
+	QetLogger::instance().init();
+	const QStringList files = QetLogger::instance().pendingCrashDumpFiles();
+
+	QCOMPARE(files.size(), 3);
+	QVERIFY(files.at(0).endsWith(QStringLiteral("crash_c.log")));
+	QVERIFY(files.at(1).endsWith(QStringLiteral("crash_b.log")));
+	QVERIFY(files.at(2).endsWith(QStringLiteral("crash_a.log")));
+}
+
+/**
+	A zero-length dump means the handler opened the file and died before
+	writing anything. There is nothing to show, and offering an empty
+	report would be worse than offering none.
+*/
+void tst_CrashDumps::skipsEmptyDumps()
+{
+	writeDump(QStringLiteral("crash_empty.log"), QByteArray());
+	writeDump(QStringLiteral("crash_real.log"), "something");
+
+	QetLogger::instance().init();
+	const QStringList files = QetLogger::instance().pendingCrashDumpFiles();
+
+	QCOMPARE(files.size(), 1);
+	QVERIFY(files.at(0).endsWith(QStringLiteral("crash_real.log")));
+}
+
+/**
+	The dump this run would write if it crashed must never appear in the
+	list of dumps from *previous* runs -- otherwise a process that crashed
+	could be offered its own dump, mid-crash.
+*/
+void tst_CrashDumps::excludesThisRunsOwnDump()
+{
+	writeDump(QStringLiteral("crash_previous.log"), "from a previous run");
+
+	QetLogger &logger = QetLogger::instance();
+	logger.init();
+	logger.installCrashHandler();   // this is what fixes our own path
+
+	// installCrashHandler() picked crash_<yyyyMMdd-hhmmss>_<pid>.log for
+	// this process but has not created it -- the handler only writes when
+	// the process actually dies. Standing in for that here: fill in every
+	// name it could have chosen, so whichever one it picked now exists
+	// and is non-empty. The exact second does not have to be guessed.
+	const qint64 pid = QCoreApplication::applicationPid();
+	const QDateTime now = QDateTime::currentDateTime();
+	for (int offset = -2 ; offset <= 0 ; ++offset) {
+		writeDump(QStringLiteral("crash_%1_%2.log")
+				  .arg(now.addSecs(offset).toString(QStringLiteral("yyyyMMdd-hhmmss")))
+				  .arg(pid),
+			  "this run's own dump, mid-crash");
+	}
+
+	// Exactly one of those three is the path install() actually chose,
+	// and exactly that one must be missing from the list. The other two
+	// are ordinary files as far as the logger is concerned.
+	const QDir dir(crashesDir());
+	const int on_disk = dir.entryList({QStringLiteral("crash_*_") + QString::number(pid)
+						  + QStringLiteral(".log")},
+					  QDir::Files).size();
+	QCOMPARE(on_disk, 3);
+
+	const QStringList files = logger.pendingCrashDumpFiles();
+	int offered_own = 0;
+	for (const QString &path : files) {
+		if (path.contains(QString::number(pid))) {
+			++offered_own;
+		}
+	}
+	QCOMPARE(offered_own, 2);            // one of the three was excluded
+	QCOMPARE(files.size(), 3);           // those two, plus crash_previous.log
+	QVERIFY(files.last().endsWith(QStringLiteral("crash_previous.log")));
+}
+
+/**
+	A crash loop writes one dump per restart. The list is capped so the
+	dialog cannot be handed an unbounded amount of text.
+*/
+void tst_CrashDumps::capsTheListAtTenDumps()
+{
+	const QDateTime base = QDateTime::currentDateTime();
+	for (int i = 0 ; i < 15 ; ++i) {
+		writeDump(QStringLiteral("crash_%1.log").arg(i, 2, 10, QChar('0')),
+			  QByteArray("dump ") + QByteArray::number(i),
+			  base.addSecs(-1000 + i));
+	}
+
+	QetLogger::instance().init();
+	QCOMPARE(QetLogger::instance().pendingCrashDumpFiles().size(), 10);
+
+	// The ten kept are the newest ten, i.e. 05..14.
+	const QStringList files = QetLogger::instance().pendingCrashDumpFiles();
+	QVERIFY(files.at(0).endsWith(QStringLiteral("crash_14.log")));
+	QVERIFY(files.at(9).endsWith(QStringLiteral("crash_05.log")));
+}
+
+/**
+	#898: every dump is offered, not just the most recent one. The whole
+	point of keeping them is that a repeating crash is where the earlier
+	dumps carry the most information.
+*/
+void tst_CrashDumps::concatenatesEveryOfferedDump()
+{
+	const QDateTime base = QDateTime::currentDateTime();
+	writeDump(QStringLiteral("crash_one.log"), "FIRST CRASH BODY", base.addSecs(-200));
+	writeDump(QStringLiteral("crash_two.log"), "SECOND CRASH BODY", base.addSecs(-100));
+
+	QetLogger &logger = QetLogger::instance();
+	logger.init();
+
+	const QStringList offered = logger.pendingCrashDumpFiles();
+	const QByteArray content = logger.pendingCrashDumpContents(offered);
+
+	QVERIFY(content.contains("FIRST CRASH BODY"));
+	QVERIFY(content.contains("SECOND CRASH BODY"));
+	QVERIFY(content.contains("crash_one.log"));
+	QVERIFY(content.contains("crash_two.log"));
+	QVERIFY(content.contains("2 crash dumps pending"));
+}
+
+/**
+	The reason clearPendingCrashDump() takes the list rather than looking
+	the directory up again: the offer sits in a modal dialog, and a dump
+	that arrives while it is open has never been seen by anybody.
+*/
+void tst_CrashDumps::clearsOnlyWhatWasOffered()
+{
+	writeDump(QStringLiteral("crash_offered.log"), "offered to the user");
+
+	QetLogger &logger = QetLogger::instance();
+	logger.init();
+
+	const QStringList offered = logger.pendingCrashDumpFiles();
+	QCOMPARE(offered.size(), 1);
+
+	// ... the dialog is open, and a second instance crashes.
+	writeDump(QStringLiteral("crash_arrived_later.log"), "nobody has seen this yet");
+
+	logger.clearPendingCrashDump(offered);
+
+	const QStringList left = logger.pendingCrashDumpFiles();
+	QCOMPARE(left.size(), 1);
+	QVERIFY(left.at(0).endsWith(QStringLiteral("crash_arrived_later.log")));
+}
+
+void tst_CrashDumps::redactsTheHomeDirectory()
+{
+	const QByteArray home = QDir::homePath().toUtf8();
+	QVERIFY(!home.isEmpty());
+
+	const QByteArray in = home + "/projects/secret.qet failed to load";
+	const QByteArray out = QetLogger::redact(in);
+
+	QVERIFY(!out.contains(home));
+	QVERIFY(out.startsWith("~/projects/secret.qet"));
+}
+
+/**
+	backtrace_symbols_fd() writes absolute module paths, which for an
+	AppImage is a per-run mount point under /tmp/.mount_. Raised in review
+	on #905.
+*/
+void tst_CrashDumps::redactsAnAppImageMountPoint()
+{
+	const QByteArray in =
+		"/tmp/.mount_QElect6Yh2Kz/usr/bin/qelectrotech(+0x9b098e) [0x5ecf]\n"
+		"/tmp/.mount_QElect6Yh2Kz/usr/lib/libQt6Core.so.6(+0x1234) [0x7cfa]\n";
+	const QByteArray out = QetLogger::redact(in);
+
+	QVERIFY(!out.contains(".mount_QElect6Yh2Kz"));
+	QVERIFY(out.contains("<appimage>/usr/bin/qelectrotech"));
+	QVERIFY(out.contains("<appimage>/usr/lib/libQt6Core.so.6"));
+	// The frame offsets are the useful part and must survive.
+	QVERIFY(out.contains("(+0x9b098e) [0x5ecf]"));
+}
+
+void tst_CrashDumps::redactsBothInOneString()
+{
+	const QByteArray home = QDir::homePath().toUtf8();
+	const QByteArray in = home + "/Documents/a.qet\n/tmp/.mount_AbCdEf/usr/bin/qet\n";
+	const QByteArray out = QetLogger::redact(in);
+
+	QVERIFY(!out.contains(home));
+	QVERIFY(!out.contains(".mount_AbCdEf"));
+	QVERIFY(out.contains("~/Documents/a.qet"));
+	QVERIFY(out.contains("<appimage>/usr/bin/qet"));
+}
+
+QTEST_MAIN(tst_CrashDumps)
+#include "tst_crashdumps.moc"

tests/qttest/tst_crashhandler.cpp

@@ -0,0 +1,149 @@
+/*
+	Copyright 2006-2026 The QElectroTech Team
+	This file is part of QElectroTech.
+
+	QElectroTech is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 2 of the License, or
+	(at your option) any later version.
+
+	QElectroTech is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with QElectroTech.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "logging/crashhandler.h"
+
+#include <QTest>
+#include <climits>
+#include <csignal>
+#include <cstring>
+
+/**
+	@brief The tst_CrashHandler class
+
+	Covers CrashHandler::formatInt(), the decimal formatter the signal
+	handler uses to write "Signal: 11" into a crash dump.
+
+	It is worth a test out of proportion to its size. It cannot use
+	snprintf(), which is not on the POSIX async-signal-safe list, so it is
+	hand-rolled; it runs only inside a signal handler, where nothing can
+	assert and a fault produces no diagnostic; and it is exercised only
+	when the application is already crashing, so a defect here would
+	corrupt or truncate exactly the dumps that matter and would never be
+	noticed in ordinary use.
+
+	The negation is the interesting part: -value on INT_MIN is undefined
+	behaviour, so the implementation goes through unsigned.
+*/
+class tst_CrashHandler : public QObject
+{
+	Q_OBJECT
+
+	private slots:
+		void formatsZero();
+		void formatsPositive();
+		void formatsTheHandledSignals();
+		void formatsNegative();
+		void formatsIntMinWithoutOverflow();
+		void formatsIntMax();
+		void truncatesRatherThanOverflowing();
+		void writesNothingWhenThereIsNoRoom();
+
+	private:
+		/// Formats into a buffer poisoned with a sentinel, and fails if
+		/// anything past the returned length was touched.
+		static QByteArray format(int value, int size = 32);
+};
+
+QByteArray tst_CrashHandler::format(int value, int size)
+{
+	char buffer[64];
+	memset(buffer, '\xAB', sizeof(buffer));
+
+	const int len = CrashHandler::formatInt(buffer, size, value);
+
+	// Nothing may be written past what was reported, nor past `size`.
+	for (int i = qMax(len, 0) ; i < static_cast<int>(sizeof(buffer)) ; ++i) {
+		if (buffer[i] != '\xAB') {
+			return QByteArray("WROTE PAST END at ") + QByteArray::number(i);
+		}
+	}
+	if (len < 0 || len > size) {
+		return QByteArray("BAD LENGTH ") + QByteArray::number(len);
+	}
+	return QByteArray(buffer, len);
+}
+
+void tst_CrashHandler::formatsZero()
+{
+	QCOMPARE(format(0), QByteArray("0"));
+}
+
+void tst_CrashHandler::formatsPositive()
+{
+	QCOMPARE(format(1), QByteArray("1"));
+	QCOMPARE(format(9), QByteArray("9"));
+	QCOMPARE(format(10), QByteArray("10"));
+	QCOMPARE(format(1234567), QByteArray("1234567"));
+}
+
+/**
+	The values this actually sees in the field: kHandledSignals, as
+	written into the "Signal: N" line of every dump.
+*/
+void tst_CrashHandler::formatsTheHandledSignals()
+{
+	QCOMPARE(format(SIGSEGV), QByteArray::number(SIGSEGV));
+	QCOMPARE(format(SIGABRT), QByteArray::number(SIGABRT));
+	QCOMPARE(format(SIGBUS), QByteArray::number(SIGBUS));
+	QCOMPARE(format(SIGFPE), QByteArray::number(SIGFPE));
+	QCOMPARE(format(SIGILL), QByteArray::number(SIGILL));
+}
+
+void tst_CrashHandler::formatsNegative()
+{
+	QCOMPARE(format(-1), QByteArray("-1"));
+	QCOMPARE(format(-42), QByteArray("-42"));
+}
+
+/**
+	-INT_MIN is undefined behaviour; the implementation negates through
+	unsigned instead. A build that got this wrong would either trap under
+	-ftrapv/UBSan or silently print the wrong number.
+*/
+void tst_CrashHandler::formatsIntMinWithoutOverflow()
+{
+	QCOMPARE(format(INT_MIN), QByteArray::number(INT_MIN));
+}
+
+void tst_CrashHandler::formatsIntMax()
+{
+	QCOMPARE(format(INT_MAX), QByteArray::number(INT_MAX));
+}
+
+/**
+	A buffer too small must be filled and stopped at, never run past --
+	the handler passes a fixed 64-byte stack buffer and subtracts what it
+	has already used.
+*/
+void tst_CrashHandler::truncatesRatherThanOverflowing()
+{
+	QCOMPARE(format(12345, 3), QByteArray("123"));
+	QCOMPARE(format(-12345, 3), QByteArray("-12"));
+	QCOMPARE(format(7, 1), QByteArray("7"));
+}
+
+void tst_CrashHandler::writesNothingWhenThereIsNoRoom()
+{
+	QCOMPARE(format(123, 0), QByteArray());
+	QCOMPARE(format(0, 0), QByteArray());
+	QCOMPARE(format(-5, 0), QByteArray());
+}
+
+QTEST_APPLESS_MAIN(tst_CrashHandler)
+#include "tst_crashhandler.moc"