[PATCH] D119009: [Support] Ensure handlers are set up before printing the stacktrace

[Andy Yankovsky via Phabricator via llvm-commits]

werat created this revision.
Herald added subscribers: dexonsmith, hiraditya.
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On Windows `lldbassert()`[1]  will segfault[2] if `RegisterHandler()` from `lib/Support/Windows/Signals.inc` wasn't called earlier at some point (it loads `Dbghelp.dll` and initializes the function pointers [3]). The `RegisterHandler()` function is called from `RemoveFileOnSignal`, `DontRemoveFileOnSignal`, `SetInterruptFunction`, `AddSignalHandler` and `PrintStackTraceOnErrorSignal`.

For LLDB `PrintStackTraceOnErrorSignal()` is called from `InitLLVM` ctor [4], which is created in the LLDB driver [5]. However in case of using the SB API via `liblldb`, none of these functions is called and thus any `lldbassert()` will crash the process.

At first glance it seems `SBDebugger::Initialize()` can do the initialization, but `PrintStackTraceOnErrorSignal` requires `argv`, which is not available there at the moment (and I'm not sure whether this is desirable behavior for the _library_).
It's also possible to just call `RegisterHandler()` in `llvm::sys::PrintStackTrace()` to ensure the `Dbghelp.dll` is always loaded. This patch does that.

Please, let me know if this approach is OK or a different solution should be implemented.

[1] https://github.com/llvm/llvm-project/blob/0236c571810dea1b72d99ee0af124a7a09976e00/lldb/source/Utility/LLDBAssert.cpp#L45
[2] https://github.com/llvm/llvm-project/blob/0236c571810dea1b72d99ee0af124a7a09976e00/llvm/lib/Support/Windows/Signals.inc#L300
[3] https://github.com/llvm/llvm-project/blob/0236c571810dea1b72d99ee0af124a7a09976e00/llvm/lib/Support/Windows/Signals.inc#L163
[4] https://github.com/llvm/llvm-project/blob/0236c571810dea1b72d99ee0af124a7a09976e00/llvm/lib/Support/InitLLVM.cpp#L37
[5] https://github.com/llvm/llvm-project/blob/0236c571810dea1b72d99ee0af124a7a09976e00/lldb/tools/driver/Driver.cpp#L778


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D119009

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
@@ -554,7 +554,9 @@
 
 void llvm::sys::PrintStackTrace(raw_ostream &OS, int Depth) {
   // FIXME: Handle "Depth" parameter to print stack trace upto specified Depth
+  RegisterHandler();
   LocalPrintStackTrace(OS, nullptr);
+  LeaveCriticalSection(&CriticalSection);
 }
 
 void llvm::sys::SetInterruptFunction(void (*IF)()) {


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