Record the last fatal error message for crash reporting on Windows

Author: hjyamauchi

include/swift/Runtime/Debug.h

@@ -60,6 +60,13 @@ static inline const char *CRGetCrashLogMessage() {
 SWIFT_RUNTIME_ATTRIBUTE_ALWAYS_INLINE
 static inline void CRSetCrashLogMessage(const char *) {}
 
+#if defined(_WIN32)
+extern "C" {
+SWIFT_ATTRIBUTE_FOR_EXPORTS
+extern char* gLastFatalErrorMessage;
+}
+#endif // _WIN32
+
 #endif
 
 namespace swift {

stdlib/public/runtime/CrashReporter.cpp

@@ -33,3 +33,10 @@ struct crashreporter_annotations_t gCRAnnotations __attribute__((
 }
 
 #endif
+
+#if defined(_WIN32)
+extern "C" {
+SWIFT_ATTRIBUTE_FOR_EXPORTS
+char* gLastFatalErrorMessage = nullptr;
+}
+#endif

stdlib/public/runtime/Errors.cpp

@@ -70,6 +70,10 @@
 #include "swift/Runtime/Atomic.h"
 #endif // SWIFT_HAVE_CRASHREPORTERCLIENT
 
+#if defined(_WIN32)
+#include "swift/Runtime/Atomic.h"
+#endif // _WIN32
+
 #include "BacktracePrivate.h"
 
 namespace FatalErrorFlags {
@@ -299,6 +303,34 @@ reportOnCrash(uint32_t flags, const char *message)
 #else
   // empty
 #endif // SWIFT_HAVE_CRASHREPORTERCLIENT
+
+#if defined(_WIN32)
+  // The last fatal error message is accessible for crash reporting on
+  // Windows.
+  char *oldMessage = nullptr;
+  char *newMessage = nullptr;
+
+  oldMessage = std::atomic_load_explicit(
+    (volatile std::atomic<char *> *)&gLastFatalErrorMessage,
+    SWIFT_MEMORY_ORDER_CONSUME);
+
+  do {
+    if (newMessage) {
+      free(newMessage);
+      newMessage = nullptr;
+    }
+
+    if (oldMessage) {
+      swift_asprintf(&newMessage, "%s%s", oldMessage, message);
+    } else {
+      newMessage = strdup(message);
+    }
+  } while (!std::atomic_compare_exchange_strong_explicit(
+             (volatile std::atomic<char *> *)&gLastFatalErrorMessage,
+             &oldMessage, newMessage,
+             std::memory_order_release,
+             SWIFT_MEMORY_ORDER_CONSUME));
+#endif // _WIN32
 }
 
 // Report a message to system console and stderr.