Add CMake option to enable the debugging of floating point exceptions

Add a new CMake option WANT_DEBUG_FPE which adds the define
LMMS_DEBUG_FPE if activated. Extend lmmsconfig.h.in with regards to that
define. Include information about development options to the CMake
output.

Install a signal handler to trap floating point exceptions when starting
LMMS in case it is compiled using the option described above. The
current implementation of the signal handler prints a stack trace and
then exits the application.

Currently this option is only enabled for Linux builds due to
uncertainty with regards to which of the needed headers are supported by
Windows and Apple.

CMakeLists.txt

@@ -64,6 +64,7 @@ OPTION(WANT_VST		"Include VST support" ON)
 OPTION(WANT_VST_NOWINE	"Include partial VST support (without wine)" OFF)
 OPTION(WANT_WINMM	"Include WinMM MIDI support" OFF)
 OPTION(WANT_QT5		"Build with Qt5" OFF)
+OPTION(WANT_DEBUG_FPE	"Debug floating point exceptions" OFF)
 
 
 IF(LMMS_BUILD_APPLE)
@@ -420,6 +421,17 @@ IF(LMMS_BUILD_WIN32)
 	SET(STATUS_VST "OK")
 ENDIF(LMMS_BUILD_WIN32)
 
+IF(WANT_DEBUG_FPE)
+	IF(LMMS_BUILD_LINUX)
+		SET(LMMS_DEBUG_FPE TRUE)
+		SET (STATUS_DEBUG_FPE "Enabled")
+	ELSE()
+		SET (STATUS_DEBUG_FPE "Wanted but disabled due to unsupported platform")
+	ENDIF()
+ELSE()
+	SET (STATUS_DEBUG_FPE "Disabled")
+ENDIF(WANT_DEBUG_FPE)
+
 
 # check for libsamplerate
 PKG_CHECK_MODULES(SAMPLERATE REQUIRED samplerate>=0.1.8)
@@ -599,6 +611,12 @@ MESSAGE(
 "* GIG player                  : ${STATUS_GIG}\n"
 )
 
+MESSAGE(
+"Developer options\n"
+"-----------------------------------------\n"
+"* Debug FP exceptions         : ${STATUS_DEBUG_FPE}\n"
+)
+
 MESSAGE(
 "\n"
 "-----------------------------------------------------------------\n"

src/core/main.cpp

@@ -71,6 +71,33 @@
 #include "Song.h"
 #include "SetupDialog.h"
 
+#ifdef LMMS_DEBUG_FPE
+#include <fenv.h> // For feenableexcept
+#include <execinfo.h> // For backtrace and backtrace_symbols_fd
+#include <unistd.h> // For STDERR_FILENO
+#include <csignal> // To register the signal handler
+#endif
+
+
+#ifdef LMMS_DEBUG_FPE
+void signalHandler( int signum ) {
+
+	// Get a back trace
+	void *array[10];
+	size_t size;
+
+	// get void*'s for all entries on the stack
+	size = backtrace(array, 10);
+
+	backtrace_symbols_fd(array, size, STDERR_FILENO);
+
+	// cleanup and close up stuff here
+	// terminate program
+
+	exit(signum);
+}
+#endif
+
 static inline QString baseName( const QString & file )
 {
 	return QFileInfo( file ).absolutePath() + "/" +
@@ -195,6 +222,18 @@ void fileCheck( QString &file )
 
 int main( int argc, char * * argv )
 {
+#ifdef LMMS_DEBUG_FPE
+	// Enable exceptions for certain floating point results
+	feenableexcept( FE_INVALID   |
+			FE_DIVBYZERO |
+			FE_OVERFLOW  |
+			FE_UNDERFLOW);
+
+	// Install the trap handler
+	// register signal SIGFPE and signal handler
+	signal(SIGFPE, signalHandler);
+#endif
+
 	// initialize memory managers
 	MemoryManager::init();
 	NotePlayHandleManager::init();

src/lmmsconfig.h.in

@@ -21,6 +21,8 @@
 #cmakedefine LMMS_HAVE_STK
 #cmakedefine LMMS_HAVE_VST
 
+#cmakedefine LMMS_DEBUG_FPE
+
 #cmakedefine LMMS_HAVE_STDINT_H
 #cmakedefine LMMS_HAVE_STDLIB_H
 #cmakedefine LMMS_HAVE_PTHREAD_H