[clang] [clang][bytecode] Check param types against function prototype (PR #163920)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr updated https://github.com/llvm/llvm-project/pull/163920

>From ef450e122e150323df4f578ba123a22111c29b21 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Fri, 17 Oct 2025 08:48:19 +0200
Subject: [PATCH] [clang][bytecode] Check param types against function
 prototype

If the type of the ParmVarDecl and the parameter type from the
FunctionProtoType don't match, we're in for trouble. Just reject those
functions.

Fixes #163568
---
 clang/lib/AST/ByteCode/Context.cpp | 7 ++++++-
 clang/test/AST/ByteCode/c.c        | 9 +++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/clang/lib/AST/ByteCode/Context.cpp b/clang/lib/AST/ByteCode/Context.cpp
index 683e916391337..4f4b122ce8c9d 100644
--- a/clang/lib/AST/ByteCode/Context.cpp
+++ b/clang/lib/AST/ByteCode/Context.cpp
@@ -566,10 +566,15 @@ const Function *Context::getOrCreateFunction(const FunctionDecl *FuncDecl) {
 
   // Assign descriptors to all parameters.
   // Composite objects are lowered to pointers.
-  for (const ParmVarDecl *PD : FuncDecl->parameters()) {
+  const auto *FuncProto = FuncDecl->getType()->getAs<FunctionProtoType>();
+  for (auto [ParamIndex, PD] : llvm::enumerate(FuncDecl->parameters())) {
     bool IsConst = PD->getType().isConstQualified();
     bool IsVolatile = PD->getType().isVolatileQualified();
 
+    if (!getASTContext().hasSameType(PD->getType(),
+                                     FuncProto->getParamType(ParamIndex)))
+      return nullptr;
+
     OptPrimType T = classify(PD->getType());
     PrimType PT = T.value_or(PT_Ptr);
     Descriptor *Desc = P->createDescriptor(PD, PT, nullptr, std::nullopt,
diff --git a/clang/test/AST/ByteCode/c.c b/clang/test/AST/ByteCode/c.c
index 657a920e7d02c..cfdc9d0d3dd86 100644
--- a/clang/test/AST/ByteCode/c.c
+++ b/clang/test/AST/ByteCode/c.c
@@ -372,3 +372,12 @@ void discardedCmp(void)
 /// ArraySubscriptExpr that's not an lvalue
 typedef unsigned char U __attribute__((vector_size(1)));
 void nonLValueASE(U f) { f[0] = f[((U)(U){0})[0]]; }
+
+static char foo_(a) // all-warning {{definition without a prototype}}
+  char a;
+{
+  return 'a';
+}
+static void bar_(void) {
+  foo_(foo_(1));
+}