Refactor: prevent storing dangling pointers

The `_EXCEPTION_POINTERS` structure is valid only within the context of
the `UnhandledExceptionFilter` function.

After the function exits, the memory referenced by the pointer might no
longer be valid or the exception information.

The solution for this was to create `BLI_system_backtrace_with_os_info`
and passing a system-specific data as the second argument.
`BLI_system_backtrace` calls `BLI_system_backtrace_with_os_info` with a
null second argument internally.

Pull Request: https://projects.blender.org/blender/blender/pulls/129999

source/blender/blenlib/BLI_system.h

@@ -16,6 +16,7 @@ extern "C" {
 
 int BLI_cpu_support_sse2(void);
 int BLI_cpu_support_sse42(void);
+void BLI_system_backtrace_with_os_info(FILE *fp, const void *os_info);
 void BLI_system_backtrace(FILE *fp);
 
 /** Get CPU brand, result is to be MEM_freeN()-ed. */

source/blender/blenlib/intern/system.c

@@ -60,7 +60,7 @@ int BLI_cpu_support_sse2(void)
 
 /* Windows stack-walk lives in system_win32.cc */
 #if !defined(_MSC_VER)
-void BLI_system_backtrace(FILE *fp)
+void BLI_system_backtrace_with_os_info(FILE *fp, const void * /*os_info*/)
 {
   /* ----------------------- */
   /* If system as execinfo.h */
@@ -97,7 +97,12 @@ void BLI_system_backtrace(FILE *fp)
 #  endif
 }
 #endif
-/* end BLI_system_backtrace */
+/* end BLI_system_backtrace_with_os_info */
+
+void BLI_system_backtrace(FILE *fp)
+{
+  BLI_system_backtrace_with_os_info(fp, NULL);
+}
 
 /* NOTE: The code for CPU brand string is adopted from Cycles. */
 

source/blender/blenlib/intern/system_win32.cc

@@ -18,8 +18,6 @@
 
 #include "BLI_system.h" /* Own include. */
 
-static EXCEPTION_POINTERS *current_exception = nullptr;
-
 static const char *bli_windows_get_exception_description(const DWORD exceptioncode)
 {
   switch (exceptioncode) {
@@ -310,14 +308,14 @@ static void bli_windows_system_backtrace_threads(FILE *fp)
   CloseHandle(hThreadSnap);
 }
 
-static bool BLI_windows_system_backtrace_stack(FILE *fp)
+static bool bli_windows_system_backtrace_stack(FILE *fp, const EXCEPTION_POINTERS *exception_info)
 {
   fprintf(fp, "Stack trace:\n");
   /* If we are handling an exception use the context record from that. */
-  if (current_exception && current_exception->ExceptionRecord->ExceptionAddress) {
+  if (exception_info && exception_info->ExceptionRecord->ExceptionAddress) {
     /* The back trace code will write to the context record, to protect the original record from
      * modifications give the backtrace a copy to work on. */
-    CONTEXT TempContext = *current_exception->ContextRecord;
+    CONTEXT TempContext = *exception_info->ContextRecord;
     return BLI_windows_system_backtrace_run_trace(fp, GetCurrentThread(), &TempContext);
   }
   else {
@@ -383,14 +381,15 @@ static void bli_load_symbols()
 /**
  * Write a backtrace into a file for systems which support it.
  */
-void BLI_system_backtrace(FILE *fp)
+void BLI_system_backtrace_with_os_info(FILE *fp, const void *os_info)
 {
+  const EXCEPTION_POINTERS *exception_info = static_cast<const EXCEPTION_POINTERS *>(os_info);
   SymInitialize(GetCurrentProcess(), nullptr, TRUE);
   bli_load_symbols();
-  if (current_exception) {
-    bli_windows_system_backtrace_exception_record(fp, current_exception->ExceptionRecord);
+  if (exception_info) {
+    bli_windows_system_backtrace_exception_record(fp, exception_info->ExceptionRecord);
   }
-  if (BLI_windows_system_backtrace_stack(fp)) {
+  if (bli_windows_system_backtrace_stack(fp, exception_info)) {
     /* When the blender symbols are missing the stack traces will be unreliable
      * so only run if the previous step completed successfully. */
     bli_windows_system_backtrace_threads(fp);
@@ -400,15 +399,14 @@ void BLI_system_backtrace(FILE *fp)
 
 void BLI_windows_handle_exception(void *exception)
 {
-  current_exception = static_cast<EXCEPTION_POINTERS *>(exception);
-  if (current_exception) {
-    fprintf(
-        stderr,
-        "Error   : %s\n",
-        bli_windows_get_exception_description(current_exception->ExceptionRecord->ExceptionCode));
+  const EXCEPTION_POINTERS *exception_info = static_cast<EXCEPTION_POINTERS *>(exception);
+  if (exception_info) {
+    fprintf(stderr,
+            "Error   : %s\n",
+            bli_windows_get_exception_description(exception_info->ExceptionRecord->ExceptionCode));
     fflush(stderr);
 
-    LPVOID address = current_exception->ExceptionRecord->ExceptionAddress;
+    LPVOID address = exception_info->ExceptionRecord->ExceptionAddress;
     fprintf(stderr, "Address : 0x%p\n", address);
 
     CHAR modulename[MAX_PATH];

source/creator/creator_signals.cc

@@ -81,13 +81,7 @@ static void sig_handle_blender_esc(int sig)
   }
 }
 
-static void sig_handle_crash_backtrace(FILE *fp)
-{
-  fputs("\n# backtrace\n", fp);
-  BLI_system_backtrace(fp);
-}
-
-static void sig_handle_crash(int signum)
+static void sig_handle_crash_backtrace(int signum, const void *os_info)
 {
   /* Might be called after WM/Main exit, so needs to be careful about nullptr-checking before
    * de-referencing. */
@@ -136,7 +130,8 @@ static void sig_handle_crash(int signum)
       BKE_report_write_file_fp(fp, &wm->runtime->reports, header);
     }
 
-    sig_handle_crash_backtrace(fp);
+    fputs("\n# backtrace\n", fp);
+    BLI_system_backtrace_with_os_info(fp, os_info);
 
 #  ifdef WITH_PYTHON
     /* Generate python back-trace if Python is currently active. */
@@ -158,6 +153,11 @@ static void sig_handle_crash(int signum)
 #  endif
 }
 
+static void sig_handle_crash_fn(int signum)
+{
+  sig_handle_crash_backtrace(signum, nullptr);
+}
+
 #  ifdef WIN32
 extern LONG WINAPI windows_exception_handler(EXCEPTION_POINTERS *ExceptionInfo)
 {
@@ -177,7 +177,7 @@ extern LONG WINAPI windows_exception_handler(EXCEPTION_POINTERS *ExceptionInfo)
   }
   else {
     BLI_windows_handle_exception(ExceptionInfo);
-    sig_handle_crash(SIGSEGV);
+    sig_handle_crash_backtrace(SIGSEGV, ExceptionInfo);
   }
 
   return EXCEPTION_EXECUTE_HANDLER;
@@ -197,7 +197,7 @@ void main_signal_setup()
     SetUnhandledExceptionFilter(windows_exception_handler);
 #  else
     /* After parsing arguments. */
-    signal(SIGSEGV, sig_handle_crash);
+    signal(SIGSEGV, sig_handle_crash_fn);
 #  endif
   }