From 15ab37321cbdb8c38e30cf8bd59bad52f4497580 Mon Sep 17 00:00:00 2001
From: Alp Toker <alp@nuanti.com>
Date: Thu, 12 Dec 2013 12:47:48 +0000
Subject: [PATCH] Suppress -Wshadow / -Wold-style-cast expanded from system
 header macros

Thanks to Jonathan Sauer for providing initial test cases.

Fixes PR16093 and PR18147.

llvm-svn: 197150
---
 clang/lib/Sema/SemaDecl.cpp                 |  2 ++
 clang/lib/Sema/SemaExpr.cpp                 |  6 ++--
 clang/test/SemaCXX/warn-sysheader-macro.cpp | 35 +++++++++++++++++++++
 3 files changed, 40 insertions(+), 3 deletions(-)
 create mode 100644 clang/test/SemaCXX/warn-sysheader-macro.cpp

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index cd28c228c065..aa2104e0aac4 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -5599,6 +5599,8 @@ void Sema::CheckShadow(Scope *S, VarDecl *D, const LookupResult& R) {
   DeclarationName Name = R.getLookupName();
 
   // Emit warning and note.
+  if (getSourceManager().isInSystemMacro(R.getNameLoc()))
+    return;
   Diag(R.getNameLoc(), diag::warn_decl_shadow) << Name << Kind << OldDC;
   Diag(ShadowedDecl->getLocation(), diag::note_previous_declaration);
 }
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 66ca9d40d831..d1e3c1f41e2e 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -5143,9 +5143,9 @@ Sema::ActOnCastExpr(Scope *S, SourceLocation LParenLoc,
     CastExpr = Result.take();
   }
 
-  if (getLangOpts().CPlusPlus && !castType->isVoidType())
-    Diag(CastExpr->getLocStart(), diag::warn_old_style_cast)
-        << SourceRange(LParenLoc, RParenLoc);
+  if (getLangOpts().CPlusPlus && !castType->isVoidType() &&
+      !getSourceManager().isInSystemMacro(LParenLoc))
+    Diag(LParenLoc, diag::warn_old_style_cast) << CastExpr->getSourceRange();
 
   return BuildCStyleCastExpr(LParenLoc, castTInfo, RParenLoc, CastExpr);
 }
diff --git a/clang/test/SemaCXX/warn-sysheader-macro.cpp b/clang/test/SemaCXX/warn-sysheader-macro.cpp
new file mode 100644
index 000000000000..c88461720ad4
--- /dev/null
+++ b/clang/test/SemaCXX/warn-sysheader-macro.cpp
@@ -0,0 +1,35 @@
+// RUN: %clang_cc1 -verify -fsyntax-only -Wshadow -Wold-style-cast %s
+
+// Test that macro expansions from system headers don't trigger 'syntactic'
+// warnings that are not actionable.
+
+#ifdef IS_SYSHEADER
+#pragma clang system_header
+
+#define SANITY(a) (a / 0)
+
+#define SHADOW(a) __extension__({ int v = a; v; })
+
+#define OLD_STYLE_CAST(a) ((int) (a))
+
+#else
+
+#define IS_SYSHEADER
+#include __FILE__
+
+void testSanity() {
+  // Validate that the test is set up correctly
+  int i = SANITY(0); // expected-warning {{division by zero is undefined}}
+}
+
+void PR16093() {
+  // no -Wshadow in system macro expansion
+  int i = SHADOW(SHADOW(1));
+}
+
+void PR18147() {
+  // no -Wold_style_cast in system macro expansion
+  int i = OLD_STYLE_CAST(0);
+}
+
+#endif