[Clang][Sema] Fix out-of-bounds access

[Sirraide]

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.

[llvmbot]

@llvm/pr-subscribers-clang

Author: None (Sirraide)

Changes

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 --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

[Sirraide]

CC @AaronBallman

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[Sirraide]

If you’re wondering what the force-pushes are about, first I forgot to run git clang-format, then I was also missing a newline at the end of the test file...

[cor3ntin]

LGTM, thanks!

[Sirraide]

LGTM, thanks!

I don’t have commit access, so you or someone else would have to merge it