r316166 - Fix nodiscard for volatile references

[Erich Keane via cfe-commits]

Author: erichkeane
Date: Thu Oct 19 08:58:58 2017
New Revision: 316166

URL: http://llvm.org/viewvc/llvm-project?rev=316166&view=rev
Log:
Fix nodiscard for volatile references

As reported here https://bugs.llvm.org/show_bug.cgi?id=34988
[[nodiscard]] warnings were not being suppressed for
volatile-ref return values.

Differential Revision: https://reviews.llvm.org/D39075

Modified:
    cfe/trunk/lib/AST/Expr.cpp
    cfe/trunk/test/CXX/dcl.dcl/dcl.attr/dcl.attr.nodiscard/p2.cpp

Modified: cfe/trunk/lib/AST/Expr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/Expr.cpp?rev=316166&r1=316165&r2=316166&view=diff
==============================================================================
--- cfe/trunk/lib/AST/Expr.cpp (original)
+++ cfe/trunk/lib/AST/Expr.cpp Thu Oct 19 08:58:58 2017
@@ -2298,7 +2298,8 @@ bool Expr::isUnusedResultAWarning(const
         const DeclRefExpr *DRE =
             dyn_cast<DeclRefExpr>(CE->getSubExpr()->IgnoreParens());
         if (!(DRE && isa<VarDecl>(DRE->getDecl()) &&
-              cast<VarDecl>(DRE->getDecl())->hasLocalStorage())) {
+              cast<VarDecl>(DRE->getDecl())->hasLocalStorage()) &&
+            !isa<CallExpr>(CE->getSubExpr()->IgnoreParens())) {
           return CE->getSubExpr()->isUnusedResultAWarning(WarnE, Loc,
                                                           R1, R2, Ctx);
         }

Modified: cfe/trunk/test/CXX/dcl.dcl/dcl.attr/dcl.attr.nodiscard/p2.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/dcl.dcl/dcl.attr/dcl.attr.nodiscard/p2.cpp?rev=316166&r1=316165&r2=316166&view=diff
==============================================================================
--- cfe/trunk/test/CXX/dcl.dcl/dcl.attr/dcl.attr.nodiscard/p2.cpp (original)
+++ cfe/trunk/test/CXX/dcl.dcl/dcl.attr/dcl.attr.nodiscard/p2.cpp Thu Oct 19 08:58:58 2017
@@ -9,21 +9,33 @@ enum [[nodiscard]] E {};
 E get_e();
 
 [[nodiscard]] int get_i();
+[[nodiscard]] volatile int &get_vi();
 
 void f() {
   get_s(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
   get_i(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  get_vi(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
   get_e(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
 
   // Okay, warnings are not encouraged
   get_s_ref();
   (void)get_s();
   (void)get_i();
+  (void)get_vi();
   (void)get_e();
 }
 
+[[nodiscard]] volatile char &(*fp)();
+void g() {
+  fp(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+  // OK, warning suppressed.
+  (void)fp();
+}
 #ifdef EXT
 // expected-warning at 4 {{use of the 'nodiscard' attribute is a C++17 extension}}
 // expected-warning at 8 {{use of the 'nodiscard' attribute is a C++17 extension}}
 // expected-warning at 11 {{use of the 'nodiscard' attribute is a C++17 extension}}
+// expected-warning at 12 {{use of the 'nodiscard' attribute is a C++17 extension}}
+// expected-warning at 28 {{use of the 'nodiscard' attribute is a C++17 extension}}
 #endif