From 13b6d0b447a87859900d9685f5524159f7b4bcaf Mon Sep 17 00:00:00 2001
From: patchzyy <64382339+patchzyy@users.noreply.github.com>
Date: Mon, 31 Aug 2026 16:28:24 +0200
Subject: [PATCH] Refine SEH crash handling on Windows

---
 runtime/src/main.cpp | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/runtime/src/main.cpp b/runtime/src/main.cpp
index 316220e..2ae8ed8 100644
--- a/runtime/src/main.cpp
+++ b/runtime/src/main.cpp
@@ -921,6 +921,7 @@ constexpr DWORD kCppExceptionCodeMsvc = 0xE06D7363;
 // AddressSanitizer uses STATUS_FATAL_APP_EXIT when it detects an error and wants to report it.
 // We must let ASan's handler run so it can print file/line information.
 constexpr DWORD kAsanFatalAppExit = 0x40000015; // STATUS_FATAL_APP_EXIT
+LONG ReportFatalSehAndExit(EXCEPTION_POINTERS* info);
 
 void ReportStructuredException(EXCEPTION_POINTERS* info) {
     if (!info || !info->ExceptionRecord) {
@@ -1022,13 +1023,34 @@ LONG CALLBACK SehLogger(EXCEPTION_POINTERS* info) {
         info->ExceptionRecord->ExceptionCode == kAsanFatalAppExit) { // ASan reporting - let it print first
         return EXCEPTION_CONTINUE_SEARCH;
     }
-    
+    // Software-raised exceptions (customer bit set) are used for internal control flow by
+    // system DLLs (e.g. msxml6 while mscms parses a display colour profile) and are caught
+    // by their own frame handlers. Only hardware faults are fatal at first chance; anything
+    // else that truly goes unhandled reaches UnhandledSehFilter.
+    if ((info->ExceptionRecord->ExceptionCode & 0x20000000u) != 0) {
+        return EXCEPTION_CONTINUE_SEARCH;
+    }
+    return ReportFatalSehAndExit(info);
+}
+
+LONG WINAPI UnhandledSehFilter(EXCEPTION_POINTERS* info) {
+    if (info == nullptr || info->ExceptionRecord == nullptr) {
+        return EXCEPTION_CONTINUE_SEARCH;
+    }
+    const DWORD code = info->ExceptionRecord->ExceptionCode;
+    if (code == kCppExceptionCodeGcc || code == kCppExceptionCodeMsvc || code == kAsanFatalAppExit) {
+        return EXCEPTION_CONTINUE_SEARCH;
+    }
+    return ReportFatalSehAndExit(info);
+}
+
+LONG ReportFatalSehAndExit(EXCEPTION_POINTERS* info) {
     // Guard against re-entrancy: if we crash while reporting, don't recurse
     static std::atomic_flag s_inCrashHandler = ATOMIC_FLAG_INIT;
     if (s_inCrashHandler.test_and_set()) {
         std::_Exit(EXIT_FAILURE);
     }
-    
+
     // Report the structured exception with detailed information
     ReportStructuredException(info);
     const auto* record = info->ExceptionRecord;
@@ -1063,6 +1085,7 @@ LONG CALLBACK SehLogger(EXCEPTION_POINTERS* info) {
 void InstallSehLogger() {
     if (!g_vectoredSehHandle) {
         g_vectoredSehHandle = AddVectoredExceptionHandler(1, SehLogger);
+        SetUnhandledExceptionFilter(UnhandledSehFilter);
     }
 }
 #else