display messages of unhandled c++ exceptions

loader/src/platform/windows/crashlog.cpp

@@ -20,6 +20,7 @@
 #include <iostream>
 #include <string>
 #include <fmt/core.h>
+#include "ehdata_structs.hpp"
 
 using namespace geode::prelude;
 
@@ -199,6 +200,41 @@ static std::string getRegisters(PCONTEXT context) {
 
 static std::string getInfo(LPEXCEPTION_POINTERS info, Mod* faultyMod) {
     std::stringstream stream;
+
+    if (info->ExceptionRecord->ExceptionCode == EH_EXCEPTION_NUMBER) {
+        // This executes when a C++ exception was thrown and not handled.
+        // https://devblogs.microsoft.com/oldnewthing/20100730-00/?p=13273
+
+        bool isStdException = false;
+
+        auto exceptionRecord = info->ExceptionRecord;
+        auto exceptionObject = exceptionRecord->ExceptionInformation[1];
+
+        auto throwInfo = reinterpret_cast<_ThrowInfo*>(exceptionRecord->ExceptionInformation[2]);
+        auto catchableTypeArray = reinterpret_cast<_CatchableTypeArray*>(throwInfo->pCatchableTypeArray);
+        auto ctaSize = catchableTypeArray->nCatchableTypes;
+
+        for (int i = 0; i < ctaSize; i++) {
+            auto catchableType = reinterpret_cast<_CatchableType*>(catchableTypeArray->arrayOfCatchableTypes[i]);
+            auto ctDescriptor = reinterpret_cast<_TypeDescriptor*>(catchableType->pType);
+            auto classname = ctDescriptor->name;
+
+            if (strcmp(classname, ".?AVexception@std@@") == 0) {
+                isStdException = true;
+                break;
+            }
+        }
+
+        if (isStdException) {
+            auto excObject = reinterpret_cast<std::exception*>(exceptionObject);
+            // stream << "C++ Exception Type: " << typeid(excObject).name() << "\n"; // always const std::exception *
+            stream << "C++ Exception: " << excObject->what() << "\n";
+        } else {
+            stream << "C++ Exception: <Unknown type>\n";
+        }
+
+        stream << "Faulty Mod: " << (faultyMod ? faultyMod->getID() : "<Unknown>") << "\n";
+    } else {
         stream << "Faulty Module: "
             << getModuleName(handleFromAddress(info->ExceptionRecord->ExceptionAddress), true)
             << "\n"
@@ -212,6 +248,7 @@ static std::string getInfo(LPEXCEPTION_POINTERS info, Mod* faultyMod) {
         stream << ")"
             << "\n"
             << "Number Parameters: " << info->ExceptionRecord->NumberParameters << "\n";
+    }
     return stream.str();
 }
 

loader/src/platform/windows/ehdata_structs.hpp

@@ -0,0 +1,46 @@
+#pragma once
+// All of those are defined in <ehdata.h> but the header fails to compile for some reason.
+
+#define EH_EXCEPTION_NUMBER ('msc' | 0xE0000000)
+
+typedef struct _PMD
+{
+    int mdisp;
+    int pdisp;
+    int vdisp;
+} _PMD;
+
+typedef void (*_PMFN) (void);
+
+#pragma warning (disable:4200)
+#pragma pack (push, _TypeDescriptor, 8)
+typedef struct _TypeDescriptor
+{
+    const void *pVFTable;
+    void *spare;
+    char name [];
+} _TypeDescriptor;
+#pragma pack (pop, _TypeDescriptor)
+#pragma warning (default:4200)
+
+typedef const struct _s__CatchableType {
+    unsigned int properties;
+    _TypeDescriptor *pType;
+    _PMD thisDisplacement;
+    int sizeOrOffset;
+    _PMFN copyFunction;
+} _CatchableType;
+
+#pragma warning (disable:4200)
+typedef const struct _s__CatchableTypeArray {
+    int nCatchableTypes;
+    _CatchableType *arrayOfCatchableTypes [];
+} _CatchableTypeArray;
+#pragma warning (default:4200)
+
+typedef const struct _s__ThrowInfo {
+    unsigned int attributes;
+    _PMFN pmfnUnwind;
+    int (__cdecl *pForwardCompat) (...);
+    _CatchableTypeArray *pCatchableTypeArray;
+} _ThrowInfo;