[Lldb-commits] [lldb] [lldb] Skip the WebAssembly function header for frame recognizers (PR #211806)

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<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-lldb

Author: Jonas Devlieghere (JDevlieghere)

<details>
<summary>Changes</summary>

A frame recognizer restricted to the first instruction matches when the frame's PC equals the function's start address. On WebAssembly a function begins with a non-executable local variable header, so the symbol's start address is never a value the PC can take and such recognizers never matched.

Route the start address through Architecture::SkipFunctionHeader, which already maps a function start past this header for breakpoints and disassembly, so the comparison uses the first executable instruction.

---
Full diff: https://github.com/llvm/llvm-project/pull/211806.diff


1 Files Affected:

- (modified) lldb/source/Target/StackFrameRecognizer.cpp (+9) 


``````````diff
diff --git a/lldb/source/Target/StackFrameRecognizer.cpp b/lldb/source/Target/StackFrameRecognizer.cpp
index 589f3805e3a67..788efff98f06e 100644
--- a/lldb/source/Target/StackFrameRecognizer.cpp
+++ b/lldb/source/Target/StackFrameRecognizer.cpp
@@ -7,11 +7,13 @@
 //===----------------------------------------------------------------------===//
 
 #include "lldb/Target/StackFrameRecognizer.h"
+#include "lldb/Core/Architecture.h"
 #include "lldb/Core/Module.h"
 #include "lldb/Interpreter/Interfaces/ScriptedStackFrameRecognizerInterface.h"
 #include "lldb/Interpreter/ScriptInterpreter.h"
 #include "lldb/Symbol/Symbol.h"
 #include "lldb/Target/StackFrame.h"
+#include "lldb/Target/Target.h"
 #include "lldb/Utility/RegularExpression.h"
 #include "lldb/Utility/ScriptedMetadata.h"
 
@@ -180,6 +182,13 @@ StackFrameRecognizerManager::GetRecognizerForFrame(StackFrameSP frame) {
   Address start_addr = symbol->GetAddress();
   Address current_addr = frame->GetFrameCodeAddress();
 
+  // The symbol's start address may fall inside a non-executable function
+  // header (as on WebAssembly), which no frame's PC can equal. Compare against
+  // the first instruction instead.
+  if (TargetSP target_sp = frame->CalculateTarget())
+    if (Architecture *arch = target_sp->GetArchitecturePlugin())
+      start_addr = arch->SkipFunctionHeader(start_addr);
+
   for (const auto &entry : m_recognizers) {
     if (!entry.enabled)
       continue;

``````````

</details>


https://github.com/llvm/llvm-project/pull/211806