[PATCH] D77611: [Sema] Check calls to __attribute__((warn_unused_result)) from StmtExprs

[Nick Desaulniers via Phabricator via cfe-commits]

nickdesaulniers updated this revision to Diff 255823.
nickdesaulniers added a comment.

- tighten up condition, eagerly emit diag, test with kernel before pushing


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D77611/new/

https://reviews.llvm.org/D77611

Files:
  clang/lib/Sema/SemaStmt.cpp
  clang/test/Frontend/macros.c


Index: clang/test/Frontend/macros.c
===================================================================
--- clang/test/Frontend/macros.c
+++ clang/test/Frontend/macros.c
@@ -1,5 +1,4 @@
-// RUN: %clang_cc1 -DA= -DB=1 -verify -fsyntax-only %s
-// expected-no-diagnostics
+// RUN: %clang_cc1 -Wunused-result -DA= -DB=1 -verify -fsyntax-only %s
 
 int a[(B A) == 1 ? 1 : -1];
 
@@ -11,3 +10,15 @@
 void foo(int a, int b, int c) {
   memset(a,b,c);  // No warning!
 }
+
+__attribute__((warn_unused_result)) static inline int bar(void) {
+  return 42;
+}
+
+#define baz() ({ \
+  bar();         \
+})
+
+void quux(void) {
+  baz(); // expected-warning {{ignoring return value of function declared with 'warn_unused_result' attribute}}
+}
Index: clang/lib/Sema/SemaStmt.cpp
===================================================================
--- clang/lib/Sema/SemaStmt.cpp
+++ clang/lib/Sema/SemaStmt.cpp
@@ -247,9 +247,18 @@
   // 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())
+  // false positive. But we do want to check CallExprs with
+  // WarnUnusedResultAttr.
+  if (isa<StmtExpr>(E) && Loc.isMacroID()) {
+    if (const CallExpr *CE = dyn_cast<CallExpr>(WarnExpr))
+      if (const Decl *FD = CE->getCalleeDecl())
+        if (FD->hasAttr<WarnUnusedResultAttr>())
+          DiagnoseNoDiscard(*this,
+                            cast_or_null<WarnUnusedResultAttr>(
+                                CE->getUnusedResultAttr(Context)),
+                            Loc, R1, R2, /*isCtor=*/false);
     return;
+  }
 
   // Check if this is the UNREFERENCED_PARAMETER from the Microsoft headers.
   // That macro is frequently used to suppress "unused parameter" warnings,


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D77611.255823.patch
Type: text/x-patch
Size: 1924 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20200407/60d44a64/attachment.bin>