[clang] [Clang][Sema] Fix out-of-bounds access (PR #80978)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: None (Sirraide)

<details>
<summary>Changes</summary>

Trying to compile a C-style variadic member function with an explicit object parameter was crashing in Sema because of an out-of-bounds access.

This fixes #<!-- -->80971.

---
Full diff: https://github.com/llvm/llvm-project/pull/80978.diff


2 Files Affected:

- (modified) clang/lib/Sema/SemaOverload.cpp (+1-1) 
- (modified) clang/test/SemaCXX/cxx2b-deducing-this.cpp (+10) 


``````````diff
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 6a04d68b4f0414..fc3d7d8dcf16e8 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -7719,7 +7719,7 @@ bool Sema::CheckNonDependentConversions(
   unsigned Offset =
       Method && Method->hasCXXExplicitFunctionObjectParameter() ? 1 : 0;
 
-  for (unsigned I = 0, N = std::min(ParamTypes.size(), Args.size()); I != N;
+  for (unsigned I = 0, N = std::min(ParamTypes.size() - Offset, Args.size()); I != N;
        ++I) {
     QualType ParamType = ParamTypes[I + Offset];
     if (!ParamType->isDependentType()) {
diff --git a/clang/test/SemaCXX/cxx2b-deducing-this.cpp b/clang/test/SemaCXX/cxx2b-deducing-this.cpp
index aab35828096a8e..670e72944ee82d 100644
--- a/clang/test/SemaCXX/cxx2b-deducing-this.cpp
+++ b/clang/test/SemaCXX/cxx2b-deducing-this.cpp
@@ -636,3 +636,13 @@ struct D {
     }
 };
 }
+
+namespace GH80971 {
+struct S {
+  auto f(this auto self...) {  }
+};
+
+int bug() {
+  S{}.f(0);
+}
+}
\ No newline at end of file

``````````

</details>


https://github.com/llvm/llvm-project/pull/80978