don't warn about unused values when the unused value is a statement expression expanded from a macro. This is of dubious utility in general, but is specifically a major issue for the linux kernel. This resolves PR13747.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@163034 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp
index c885d48..76410e2 100644
--- a/lib/Sema/SemaStmt.cpp
+++ b/lib/Sema/SemaStmt.cpp
@@ -160,6 +160,13 @@
!E->isUnusedResultAWarning(WarnExpr, Loc, R1, R2, Context))
return;
+ // If this is a GNU statement expression expanded from a macro, it is probably
+ // unused because it is a function-like macro that can be used as either an
+ // expression or statement. Don't warn, because it is almost certainly a
+ // false positive.
+ if (isa<StmtExpr>(E) && Loc.isMacroID())
+ return;
+
// Okay, we have an unused result. Depending on what the base expression is,
// we might want to make a more specific diagnostic. Check for one of these
// cases now.
diff --git a/test/Frontend/macros.c b/test/Frontend/macros.c
index 3170797..828c762 100644
--- a/test/Frontend/macros.c
+++ b/test/Frontend/macros.c
@@ -2,3 +2,11 @@
int a[(B A) == 1 ? 1 : -1];
+
+// PR13747 - Don't warn about unused results with statement exprs in macros.
+void stuff(int,int,int);
+#define memset(x,y,z) ({ stuff(x,y,z); x; })
+
+void foo(int a, int b, int c) {
+ memset(a,b,c); // No warning!
+}
