[PATCH] D75768: Add a warning for builtin_return_address/frame_address with > 0 argument

[Jeremy Stenglein via Phabricator via cfe-commits]

jstenglein created this revision.
jstenglein added reviewers: efriedma, lebedev.ri, rsmith, erichkeane.
jstenglein added a project: clang.
Herald added a subscriber: cfe-commits.

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.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D75768

Files:
  clang/include/clang/Basic/DiagnosticGroups.td
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/lib/Sema/SemaChecking.cpp
  clang/test/Misc/warning-wall.c
  clang/test/Sema/builtin-returnaddress.c


Index: clang/test/Sema/builtin-returnaddress.c
===================================================================
--- /dev/null
+++ clang/test/Sema/builtin-returnaddress.c
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -fsyntax-only -Wframe-address -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wmost -verify %s
+
+void* a(unsigned x) {
+return __builtin_return_address(0);
+}
+
+void* b(unsigned x) {
+return __builtin_return_address(1); // expected-warning{{calling '__builtin_return_address' with a nonzero argument is unsafe}}
+}
+
+void* c(unsigned x) {
+return __builtin_frame_address(0);
+}
+
+void* d(unsigned x) {
+return __builtin_frame_address(1); // expected-warning{{calling '__builtin_frame_address' with a nonzero argument is unsafe}}
+}
+
Index: clang/test/Misc/warning-wall.c
===================================================================
--- clang/test/Misc/warning-wall.c
+++ clang/test/Misc/warning-wall.c
@@ -16,6 +16,7 @@
 CHECK-NEXT:      -Wformat-y2k
 CHECK-NEXT:      -Wformat-invalid-specifier
 CHECK-NEXT:    -Wfor-loop-analysis
+CHECK-NEXT:    -Wframe-address
 CHECK-NEXT:    -Wimplicit
 CHECK-NEXT:      -Wimplicit-function-declaration
 CHECK-NEXT:      -Wimplicit-int
Index: clang/lib/Sema/SemaChecking.cpp
===================================================================
--- clang/lib/Sema/SemaChecking.cpp
+++ clang/lib/Sema/SemaChecking.cpp
@@ -1851,6 +1851,17 @@
   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;
   }
 
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1780,6 +1780,11 @@
 def err_illegal_union_or_anon_struct_member : Error<
   "%select{anonymous struct|union}0 member %1 has a non-trivial "
   "%sub{select_special_member_kind}2">;
+
+def warn_frame_address : Warning<
+  "calling '%0' with a nonzero argument is unsafe">,
+  InGroup<FrameAddress>, DefaultIgnore;
+
 def warn_cxx98_compat_nontrivial_union_or_anon_struct_member : Warning<
   "%select{anonymous struct|union}0 member %1 with a non-trivial "
   "%sub{select_special_member_kind}2 is incompatible with C++98">,
Index: clang/include/clang/Basic/DiagnosticGroups.td
===================================================================
--- clang/include/clang/Basic/DiagnosticGroups.td
+++ clang/include/clang/Basic/DiagnosticGroups.td
@@ -99,6 +99,7 @@
   DiagGroup<"float-conversion", [FloatOverflowConversion,
                                  FloatZeroConversion]>;
 
+def FrameAddress : DiagGroup<"frame-address">;
 def DoublePromotion : DiagGroup<"double-promotion">;
 def EnumTooLarge : DiagGroup<"enum-too-large">;
 def UnsupportedNan : DiagGroup<"unsupported-nan">;
@@ -868,6 +869,7 @@
     DeleteNonVirtualDtor,
     Format,
     ForLoopAnalysis,
+    FrameAddress,
     Implicit,
     InfiniteRecursion,
     IntInBoolContext,


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