delcypher added inline comments.
================
Comment at: clang/test/Sema/warn-calls-without-prototype.c:39
+ return a + b +c;
+}
+
----------------
delcypher wrote:
> @NoQ Any ideas about this? It seems kind of weird that when merging
> `not_a_prototype3` prototype with the K&R style definition of
> `not_a_prototype3` that the resulting FunctionDecl we see at the call site in
> `call_to_function_without_prototype3` is marked as not having a prototype.
>
> If I flip the order (see `not_a_prototype6`) then the merged declaration is
> marked as having a prototype.
>
> I'm not sure if this is a bug in `Sema::MergeFunctionDecl` or if this just a
> peculiarity of K&R style function definitions.
I suspect the problem might be here in `Sema::MergeFunctionDecl`.
```lang=c++
// C: Function types need to be compatible, not identical. This handles
// duplicate function decls like "void f(int); void f(enum X);" properly.
if (!getLangOpts().CPlusPlus &&
Context.typesAreCompatible(OldQType, NewQType)) {
const FunctionType *OldFuncType = OldQType->getAs<FunctionType>();
const FunctionType *NewFuncType = NewQType->getAs<FunctionType>();
const FunctionProtoType *OldProto = nullptr;
if (MergeTypeWithOld && isa<FunctionNoProtoType>(NewFuncType) &&
(OldProto = dyn_cast<FunctionProtoType>(OldFuncType))) {
// The old declaration provided a function prototype, but the
// new declaration does not. Merge in the prototype.
```
` isa<FunctionNoProtoType>(NewFuncType)` is false in this particular case,
however `New` doesn't have a prototype (i.e. `New->hasPrototype()` is false).
One fix might be to replace `isa<FunctionNoProtoType>(NewFuncType)` with
```
(isa<FunctionNoProtoType>(NewFuncType) || !New->hasPrototype())
```
However, I don't really know this code well enough to know if that's the right
fix.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D116635/new/
https://reviews.llvm.org/D116635
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