Add a warning to diagnose statements in C++ like "*(volatile int*)x;". Conceptually, this is part of -Wunused-value, but I added a separate flag -Wunused-volatile-lvalue so it doesn't get turned off by accident with -Wno-unused-value. I also made a few minor improvements to existing unused value warnings in the process. <rdar://problem/11516811>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@157362 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 2 deletions

diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp
index f64fc96c0e..a342cbd6cc 100644
--- a/lib/Sema/SemaStmt.cpp
+++ b/lib/Sema/SemaStmt.cpp
@@ -153,10 +153,11 @@ void Sema::DiagnoseUnusedExprResult(const Stmt *S) {
   if (!E)
     return;
 
+  const Expr *WarnExpr;
   SourceLocation Loc;
   SourceRange R1, R2;
   if (SourceMgr.isInSystemMacro(E->getExprLoc()) ||
-      !E->isUnusedResultAWarning(Loc, R1, R2, Context))
+      !E->isUnusedResultAWarning(WarnExpr, Loc, R1, R2, Context))
     return;
 
   // Okay, we have an unused result.  Depending on what the base expression is,
@@ -171,7 +172,7 @@ void Sema::DiagnoseUnusedExprResult(const Stmt *S) {
   if (DiagnoseUnusedComparison(*this, E))
     return;
 
-  E = E->IgnoreParenImpCasts();
+  E = WarnExpr;
   if (const CallExpr *CE = dyn_cast<CallExpr>(E)) {
     if (E->getType()->isVoidType())
       return;
@@ -229,6 +230,11 @@ void Sema::DiagnoseUnusedExprResult(const Stmt *S) {
     }
   }
 
+  if (E->isGLValue() && E->getType().isVolatileQualified()) {
+    Diag(Loc, diag::warn_unused_volatile) << R1 << R2;
+    return;
+  }
+
   DiagRuntimeBehavior(Loc, 0, PDiag(DiagID) << R1 << R2);
 }