[PATCH] D126522: Create specialization of `-Wgnu-statement-expression` for expressions found in macros.

[Michael Wyman via Phabricator via cfe-commits]

mwyman created this revision.
mwyman added reviewers: stephanemoore, hokein, ymandel, dmaclach.
mwyman added a project: clang.
Herald added a project: All.
mwyman requested review of this revision.
Herald added a subscriber: cfe-commits.

`-Wgnu-statement-expression` currently warns for both direct source uses of statement expressions but also macro expansions; since they may be used by macros to avoid multiple evaluation of macro arguments, engineers might want to suppress warnings when statement expressions are expanded from macros but see them if introduced directly in source code.

This change adds the warning flag `-Wgnu-statement-expression-macro` to enable/disable diagnostics generated from macro expansions.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D126522

Files:
  clang/include/clang/Basic/DiagnosticGroups.td
  clang/include/clang/Basic/DiagnosticParseKinds.td
  clang/lib/Parse/ParseExpr.cpp
  clang/test/Sema/gnu-flags.c


Index: clang/test/Sema/gnu-flags.c
===================================================================
--- clang/test/Sema/gnu-flags.c
+++ clang/test/Sema/gnu-flags.c
@@ -1,5 +1,5 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s -DNONE -Wno-gnu
-// RUN: %clang_cc1 -fsyntax-only -verify %s -DALL -Wgnu 
+// RUN: %clang_cc1 -fsyntax-only -verify %s -DALL -Wgnu
 // RUN: %clang_cc1 -fsyntax-only -verify %s -DALL -Wno-gnu \
 // RUN:   -Wgnu-alignof-expression -Wgnu-case-range -Wgnu-complex-integer -Wgnu-conditional-omitted-operand \
 // RUN:   -Wgnu-empty-initializer -Wgnu-label-as-value -Wgnu-statement-expression \
@@ -20,6 +20,7 @@
 // %clang_cc1 -fsyntax-only -verify %s -DEMPTYINIT -Wno-gnu -Wgnu-empty-initializer
 // %clang_cc1 -fsyntax-only -verify %s -DLABELVALUE -Wno-gnu -Wgnu-label-as-value
 // %clang_cc1 -fsyntax-only -verify %s -DSTATEMENTEXP -Wno-gnu -Wgnu-statement-expression
+// %clang_cc1 -fsyntax-only -verify %s -DSTATEMENTEXPMACRO -Wno-gnu -Wgnu-statement-expression-macro
 // %clang_cc1 -fsyntax-only -verify %s -DCOMPOUNDLITERALINITIALIZER -Wno-gnu -Wgnu-compound-literal-initializer
 // %clang_cc1 -fsyntax-only -verify %s -DFLEXIBLEARRAYINITIALIZER -Wno-gnu -Wgnu-flexible-array-initializer
 // %clang_cc1 -fsyntax-only -verify %s -DREDECLAREDENUM -Wno-gnu -Wgnu-redeclared-enum
@@ -95,6 +96,14 @@
 	int a = ({ 1; });
 }
 
+#if ALL || STATEMENTEXPMACRO
+// expected-warning at +5 {{use of GNU statement expression extension from macro expansion}}
+#endif
+
+#define STMT_EXPR_MACRO(a) ({ (a); })
+void statementexprmacro(void) {
+  int a = STMT_EXPR_MACRO(1);
+}
 
 #if ALL || COMPOUNDLITERALINITIALIZER
 // expected-warning at +4 {{initialization of an array of type 'int[5]' from a compound literal of type 'int[5]' is a GNU extension}}
Index: clang/lib/Parse/ParseExpr.cpp
===================================================================
--- clang/lib/Parse/ParseExpr.cpp
+++ clang/lib/Parse/ParseExpr.cpp
@@ -2870,7 +2870,8 @@
   // None of these cases should fall through with an invalid Result
   // unless they've already reported an error.
   if (ExprType >= CompoundStmt && Tok.is(tok::l_brace)) {
-    Diag(Tok, diag::ext_gnu_statement_expr);
+    Diag(Tok, OpenLoc.isMacroID() ? diag::ext_gnu_statement_expr_macro
+                                  : diag::ext_gnu_statement_expr);
 
     checkCompoundToken(OpenLoc, tok::l_paren, CompoundToken::StmtExprBegin);
 
Index: clang/include/clang/Basic/DiagnosticParseKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticParseKinds.td
+++ clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -174,6 +174,9 @@
   "statement expression not allowed at file scope">;
 def ext_gnu_statement_expr : Extension<
   "use of GNU statement expression extension">, InGroup<GNUStatementExpression>;
+def ext_gnu_statement_expr_macro : Extension<
+  "use of GNU statement expression extension from macro expansion">,
+  InGroup<GNUStatementExpressionMacro>;
 def ext_gnu_conditional_expr : Extension<
   "use of GNU ?: conditional expression extension, omitting middle operand">, InGroup<GNUConditionalOmittedOperand>;
 def ext_gnu_empty_initializer : Extension<
Index: clang/include/clang/Basic/DiagnosticGroups.td
===================================================================
--- clang/include/clang/Basic/DiagnosticGroups.td
+++ clang/include/clang/Basic/DiagnosticGroups.td
@@ -611,7 +611,11 @@
 def StaticLocalInInline : DiagGroup<"static-local-in-inline">;
 def GNUStaticFloatInit : DiagGroup<"gnu-static-float-init">;
 def StaticFloatInit : DiagGroup<"static-float-init", [GNUStaticFloatInit]>;
-def GNUStatementExpression : DiagGroup<"gnu-statement-expression">;
+// Allow differentiation between GNU statement expressions in a macro versus
+// written directly in source.
+def GNUStatementExpressionMacro : DiagGroup<"gnu-statement-expression-macro">;
+def GNUStatementExpression : DiagGroup<"gnu-statement-expression",
+                                       [GNUStatementExpressionMacro]>;
 def StringConcatation : DiagGroup<"string-concatenation">;
 def StringCompare : DiagGroup<"string-compare">;
 def StringPlusInt : DiagGroup<"string-plus-int">;


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