[PATCH v4 0/1] MR5437: kernelbase: Do not start the debugger if SEM_NOGPFAULTERRORBOX is set.

[Zebediah Figura (＠zfigura)]

--
  v4: kernelbase: Do not start the debugger if SEM_NOGPFAULTERRORBOX is set.

https://gitlab.winehq.org/wine/wine/-/merge_requests/5437

[PATCH v4 1/1] kernelbase: Do not start the debugger if SEM_NOGPFAULTERRORBOX is set.

[Zebediah Figura]

From: Zebediah Figura

Motor City Online apparently checks for a debugger by setting this flag and then
intentionally causing a page fault. If no debugger is present on Windows, the
subprocess simply dies without spawning any crash dialog. This patch emulates
that behaviour, suppressing a (harmless) crash dialog from winedbg.

This may result in legitimate failures no longer triggering a winedbg crash
dialog, if other programs happen to use SEM_NOGPFAULTERRORBOX, but the winedbg
crash dialog cannot be relied upon anyway.
---
 dlls/kernelbase/debug.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/dlls/kernelbase/debug.c b/dlls/kernelbase/debug.c
index b7df4a7c766..72cb2feef8d 100644
--- a/dlls/kernelbase/debug.c
+++ b/dlls/kernelbase/debug.c
@@ -761,9 +761,8 @@ LONG WINAPI UnhandledExceptionFilter( EXCEPTION_POINTERS *epointers )
             if (ret != EXCEPTION_CONTINUE_SEARCH) return ret;
         }

-        /* FIXME: Should check the current error mode */
-
-        if (!start_debugger_atomic( epointers ) || !NtCurrentTeb()->Peb->BeingDebugged)
+        if ((GetErrorMode() & SEM_NOGPFAULTERRORBOX) ||
+            !start_debugger_atomic( epointers ) || !NtCurrentTeb()->Peb->BeingDebugged)
             return EXCEPTION_EXECUTE_HANDLER;
     }
     return EXCEPTION_CONTINUE_SEARCH;

[Elizabeth Figura (＠zfigura)]

v3: Return EXCEPTION_EXECUTE_HANDLER in this case, not EXCEPTION_CONTINUE_SEARCH. We want to terminate the process quietly in this case, rather than raising a last-chance exception.