[PATCH] D119181: [Support] Don't print stacktrace if DbgHelp.dll hasn't been loaded yet

[Andy Yankovsky via Phabricator via llvm-commits]

werat created this revision.
werat added reviewers: aganea, JDevlieghere, labath.
Herald added subscribers: dexonsmith, hiraditya.
werat requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

On Windows certain function from `Signals.h` require that `DbgHelp.dll` is loaded. This typically happens when the main program calls `llvm::InitLLVM`, however in some cases main program doesn't do that (e.g. when the application is using LLDB via `liblldb.dll`). This patch adds a safe guard to prevent crashes. More discussion in
https://reviews.llvm.org/D119009.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D119181

Files:
  llvm/lib/Support/Windows/Signals.inc


Index: llvm/lib/Support/Windows/Signals.inc
===================================================================
--- llvm/lib/Support/Windows/Signals.inc
+++ llvm/lib/Support/Windows/Signals.inc
@@ -159,6 +159,10 @@
 typedef BOOL (WINAPI *fpEnumerateLoadedModules)(HANDLE,PENUMLOADED_MODULES_CALLBACK64,PVOID);
 static fpEnumerateLoadedModules fEnumerateLoadedModules;
 
+static bool isDebugHelpInitialized() {
+  return fStackWalk64 && fSymInitialize && fSymSetOptions && fMiniDumpWriteDump;
+}
+
 static bool load64BitDebugHelp(void) {
   HMODULE hLib = ::LoadLibraryW(L"Dbghelp.dll");
   if (hLib) {
@@ -181,7 +185,7 @@
     fEnumerateLoadedModules = (fpEnumerateLoadedModules)
       ::GetProcAddress(hLib, "EnumerateLoadedModules64");
   }
-  return fStackWalk64 && fSymInitialize && fSymSetOptions && fMiniDumpWriteDump;
+  return isDebugHelpInitialized();
 }
 
 using namespace llvm;
@@ -296,6 +300,12 @@
 static void PrintStackTraceForThread(llvm::raw_ostream &OS, HANDLE hProcess,
                                      HANDLE hThread, STACKFRAME64 &StackFrame,
                                      CONTEXT *Context) {
+  // It's possible that DbgHelp.dll hasn't been loaded yet (e.g. if this
+  // function is called before the main program called `llvm::InitLLVM`).
+  // In this case just return, not stacktrace will be printed.
+  if (!isDebugHelpInitialized())
+    return;
+
   // Initialize the symbol handler.
   fSymSetOptions(SYMOPT_DEFERRED_LOADS | SYMOPT_LOAD_LINES);
   fSymInitialize(hProcess, NULL, TRUE);


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