Add a warning for builtin_return_address/frame_address with > 0 argument

Clang is missing a warning for
builtin_return_address/builtin_frame_address called with > 0 argument.
Gcc provides a warning for this via -Wframe-address:

https://gcc.gnu.org/onlinedocs/gcc/Return-Address.html

As calling these functions with argument > 0 has caused several crashes
for us, we would like to have the same warning as gcc here. This diff
adds the warning and makes it part of -Wmost.

Differential Revision: https://reviews.llvm.org/D75768

1 files changed, 11 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 106e90f..2e73fca 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -1853,6 +1853,17 @@ Sema::CheckBuiltinFunctionCall(FunctionDecl *FDecl, unsigned BuiltinID,
   case Builtin::BI__builtin_return_address:
     if (SemaBuiltinConstantArgRange(TheCall, 0, 0, 0xFFFF))
       return ExprError();
+
+    // -Wframe-address warning if non-zero passed to builtin
+    // return/frame address.
+    Expr::EvalResult Result;
+    if (TheCall->getArg(0)->EvaluateAsInt(Result, getASTContext()) &&
+        Result.Val.getInt() != 0)
+      Diag(TheCall->getBeginLoc(), diag::warn_frame_address)
+          << ((BuiltinID == Builtin::BI__builtin_return_address)
+                  ? "__builtin_return_address"
+                  : "__builtin_frame_address")
+          << TheCall->getSourceRange();
     break;
   }