[Lldb-commits] [lldb] [lldb][CPlusPlusLanguage] Avoid redundant const char* -> StringRef roundtrip (PR #161499)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-lldb

Author: Michael Buch (Michael137)

<details>
<summary>Changes</summary>

We've been seen (very sporadic) lifetime issues around this area. Here's an example backtrace:
```
[  8] 0x0000000188e56743 libsystem_platform.dylib`_sigtramp + 55
[  9] 0x00000001181e041f LLDB`lldb_private::CPlusPlusLanguage::SymbolNameFitsToLanguage(lldb_private::Mangled) const [inlined] unsigned long std::1::constexpr_strlen[abi:nn200100]<char>(char const*) + 7 at constexpr_c_functions.h:63:10
[  9] 0x00000001181e0418 LLDB`lldb_private::CPlusPlusLanguage::SymbolNameFitsToLanguage(lldb_private::Mangled) const [inlined] std::__1::char_traits<char>::length[abi:nn200100](char const*) at char_traits.h:232:12
[  9] 0x00000001181e0418 LLDB`lldb_private::CPlusPlusLanguage::SymbolNameFitsToLanguage(lldb_private::Mangled) const [inlined] llvm::StringRef::StringRef(char const*) at StringRef.h:90:33
[  9] 0x00000001181e0418 LLDB`lldb_private::CPlusPlusLanguage::SymbolNameFitsToLanguage(lldb_private::Mangled) const [inlined] llvm::StringRef::StringRef(char const*) at StringRef.h:92:38
[  9] 0x00000001181e0418 LLDB`lldb_private::CPlusPlusLanguage::SymbolNameFitsToLanguage(lldb_private::Mangled) const + 20 at CPlusPlusLanguage.cpp:68:62
```

Looks like we're calling `strlen` on a nullptr. I stared at this codepath for a while but am still not sure how that could happen unless the underlying `ConstString` somehow pointed to corrupted data.

But `SymbolNameFitsToLanguage` does some roundtripping through a `const char*` before calling `GetManglingScheme`. No other callsite does this and it just seems redundant.

This patch cleans this up.

rdar://161128180

---
Full diff: https://github.com/llvm/llvm-project/pull/161499.diff


1 Files Affected:

- (modified) lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp (+4-4) 


``````````diff
diff --git a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
index 4e8a430af8c6c..a2199cb65cd35 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
@@ -104,10 +104,10 @@ CPlusPlusLanguage::GetFunctionNameInfo(ConstString name) const {
 }
 
 bool CPlusPlusLanguage::SymbolNameFitsToLanguage(Mangled mangled) const {
-  const char *mangled_name = mangled.GetMangledName().GetCString();
-  auto mangling_scheme = Mangled::GetManglingScheme(mangled_name);
-  return mangled_name && (mangling_scheme == Mangled::eManglingSchemeItanium ||
-                          mangling_scheme == Mangled::eManglingSchemeMSVC);
+  auto mangling_scheme =
+      Mangled::GetManglingScheme(mangled.GetMangledName().GetStringRef());
+  return mangling_scheme == Mangled::eManglingSchemeItanium ||
+         mangling_scheme == Mangled::eManglingSchemeMSVC;
 }
 
 ConstString CPlusPlusLanguage::GetDemangledFunctionNameWithoutArguments(

``````````

</details>


https://github.com/llvm/llvm-project/pull/161499