In C++, if the user redeclares a builtin function with a type that is

inconsistent with the type that the builtin *should* have, forget
about the builtin altogether: we don't want subsequence analyses,
CodeGen, etc., to think that we have a proper builtin function.

C is protected from errors here because it allows one to use a
library builtin without having a declaration, and detects inconsistent
(re-)declarations of builtins during declaration merging. C++ was
unprotected, and therefore would crash.

Fixes PR8839.

llvm-svn: 122351

2 files changed, 16 insertions, 0 deletions

diff --git a/clang/lib/Basic/Builtins.cpp b/clang/lib/Basic/Builtins.cpp
index 3eacb3aa611..9ecb0c0c8b7 100644
--- a/clang/lib/Basic/Builtins.cpp
+++ b/clang/lib/Basic/Builtins.cpp
@@ -80,6 +80,10 @@ Builtin::Context::GetBuiltinNames(llvm::SmallVectorImpl<const char *> &Names,
       Names.push_back(TSRecords[i].Name);
 }
 
+void Builtin::Context::ForgetBuiltin(unsigned ID, IdentifierTable &Table) {
+  Table.get(GetRecord(ID).Name).setBuiltinID(0);
+}
+
 bool
 Builtin::Context::isPrintfLike(unsigned ID, unsigned &FormatIdx,
                                bool &HasVAListArg) {
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index ad0c077aad4..bc91eb04396 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -4285,6 +4285,18 @@ void Sema::CheckFunctionDeclaration(Scope *S, FunctionDecl *NewFD,
     // during delayed parsing anyway.
     if (!CurContext->isRecord())
       CheckCXXDefaultArguments(NewFD);
+    
+    // If this function declares a builtin function, check the type of this
+    // declaration against the expected type for the builtin. 
+    if (unsigned BuiltinID = NewFD->getBuiltinID()) {
+      ASTContext::GetBuiltinTypeError Error;
+      QualType T = Context.GetBuiltinType(BuiltinID, Error);
+      if (!T.isNull() && !Context.hasSameType(T, NewFD->getType())) {
+        // The type of this function differs from the type of the builtin,
+        // so forget about the builtin entirely.
+        Context.BuiltinInfo.ForgetBuiltin(BuiltinID, Context.Idents);
+      }
+    }
   }
 }