2 files changed, 18 insertions, 1 deletions
diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index f8668c38932..869ea1deb0b 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -195,7 +195,7 @@ void Sema::DiagnoseUnusedExprResult(const Stmt *S) {
   if (isUnevaluatedContext())
     return;
 
-  SourceLocation ExprLoc = E->IgnoreParens()->getExprLoc();
+  SourceLocation ExprLoc = E->IgnoreParenImpCasts()->getExprLoc();
   // In most cases, we don't want to warn if the expression is written in a
   // macro body, or if the macro comes from a system header. If the offending
   // expression is a call to a function with the warn_unused_result attribute,
@@ -218,6 +218,15 @@ void Sema::DiagnoseUnusedExprResult(const Stmt *S) {
   if (isa<StmtExpr>(E) && Loc.isMacroID())
     return;
 
+  // Check if this is the UNREFERENCED_PARAMETER from the Microsoft headers.
+  // That macro is frequently used to suppress "unused parameter" warnings,
+  // but its implementation makes clang's -Wunused-value fire.  Prevent this.
+  if (isa<ParenExpr>(E->IgnoreImpCasts()) && Loc.isMacroID()) {
+    SourceLocation SpellLoc = Loc;
+    if (findMacroSpelling(SpellLoc, "UNREFERENCED_PARAMETER"))
+      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/clang/test/Sema/unused-expr.c b/clang/test/Sema/unused-expr.c
index 43d8150b02c..09359687d53 100644
--- a/clang/test/Sema/unused-expr.c
+++ b/clang/test/Sema/unused-expr.c
@@ -156,3 +156,11 @@ void t11(int i, int j) {
 #undef M5
 #undef M6
 #undef M7
+
+#define UNREFERENCED_PARAMETER(x) (x)
+
+void unused_parm(int a) {
+  // Don't warn if the warning is introduced by a macro that's spelled
+  // UNREFERENCED_PARAMETER, as that's a commonly used macro in Windows headers.
+  UNREFERENCED_PARAMETER(a);
+}