Add API for getting last internal error message (#5772)

* Add API for getting last internal error message

* format code (#5773)

Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

* make message thread_local

---------

Co-authored-by: slangbot <ellieh+slangbot@nvidia.com>
Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

Author: skallweitNV

include/slang.h

@@ -4415,6 +4415,10 @@ SLANG_API ISlangBlob* slang_getEmbeddedCoreModule();
  */
 SLANG_EXTERN_C SLANG_API void slang_shutdown();
 
+/* Return the last signaled internal error message.
+ */
+SLANG_EXTERN_C SLANG_API const char* slang_getLastInternalErrorMessage();
+
 namespace slang
 {
 inline SlangResult createGlobalSession(slang::IGlobalSession** outGlobalSession)
@@ -4425,6 +4429,10 @@ inline void shutdown()
 {
     slang_shutdown();
 }
+inline const char* getLastInternalErrorMessage()
+{
+    return slang_getLastInternalErrorMessage();
+}
 } // namespace slang
 
 #endif // C++ helpers

source/core/slang-signal.cpp

@@ -6,6 +6,8 @@
 namespace Slang
 {
 
+thread_local String g_lastSignalMessage;
+
 static const char* _getSignalTypeAsText(SignalType type)
 {
     switch (type)
@@ -54,6 +56,8 @@ String _getMessage(SignalType type, char const* message)
         printf("%s\n", _getMessage(type, message).getBuffer());
     }
 
+    g_lastSignalMessage = _getMessage(type, message);
+
 #if SLANG_HAS_EXCEPTIONS
     switch (type)
     {
@@ -75,4 +79,9 @@ String _getMessage(SignalType type, char const* message)
 #endif
 }
 
+const char* getLastSignalMessage()
+{
+    return g_lastSignalMessage.getBuffer();
+}
+
 } // namespace Slang

source/core/slang-signal.h

@@ -35,6 +35,8 @@ enum class SignalType
     ::Slang::handleSignal(::Slang::SignalType::AbortCompilation, msg)
 
 
+const char* getLastSignalMessage();
+
 } // namespace Slang
 
 #endif

source/slang/slang-api.cpp

@@ -3,6 +3,7 @@
 #include "../core/slang-performance-profiler.h"
 #include "../core/slang-rtti-info.h"
 #include "../core/slang-shared-library.h"
+#include "../core/slang-signal.h"
 #include "../slang-record-replay/record/slang-global-session.h"
 #include "../slang-record-replay/util/record-utility.h"
 #include "slang-capability.h"
@@ -173,6 +174,11 @@ SLANG_API SlangResult slang_createGlobalSessionWithoutCoreModule(
     return SLANG_OK;
 }
 
+SLANG_API const char* slang_getLastInternalErrorMessage()
+{
+    return Slang::getLastSignalMessage();
+}
+
 SLANG_API void spDestroySession(SlangSession* inSession)
 {
     if (!inSession)