From: Jason Merrill <jason@redhat.com>
Date: Sun, 15 Sep 2024 09:34:43 +0000 (+0200)
Subject: c++: __extension__ and -Wconditionally-supported
X-Git-Tag: basepoints/gcc-16~5898
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a9f9391e1eeccb9d062b9e73ef27ac577b23ed64;p=thirdparty%2Fgcc.git

c++: __extension__ and -Wconditionally-supported

When we're explicitly choosing GCC extensions, we similarly shouldn't
complain about optional features that GCC provides.  This particular pattern
of cast between function and object pointer is used by gthr-posix.h on some
targets, including linux-gnu before glibc 2.34.

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_unary_expression) [RID_EXTENSION]: Also
	suppress -Wconditionally-supported.

gcc/testsuite/ChangeLog:

	* g++.dg/warn/Wconditionally-supported-1.C: Add __extension__ cases.
---

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 3c8c75575b0..4dd9474cf60 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -9150,9 +9150,15 @@ cp_parser_unary_expression (cp_parser *parser, cp_id_kind * pidk,
 
 	    /* Save away the PEDANTIC flag.  */
 	    cp_parser_extension_opt (parser, &saved_pedantic);
+	    /* Also suppress -Wconditionally-supported.  */
+	    diagnostic_push_diagnostics (global_dc, input_location);
+	    diagnostic_classify_diagnostic
+	      (global_dc, OPT_Wconditionally_supported,
+	       DK_IGNORED, input_location);
 	    /* Parse the cast-expression.  */
 	    expr = cp_parser_simple_cast_expression (parser);
 	    /* Restore the PEDANTIC flag.  */
+	    diagnostic_pop_diagnostics (global_dc, input_location);
 	    pedantic = saved_pedantic;
 
 	    return expr;
diff --git a/gcc/testsuite/g++.dg/warn/Wconditionally-supported-1.C b/gcc/testsuite/g++.dg/warn/Wconditionally-supported-1.C
index 3c32edba8ce..192d709fd79 100644
--- a/gcc/testsuite/g++.dg/warn/Wconditionally-supported-1.C
+++ b/gcc/testsuite/g++.dg/warn/Wconditionally-supported-1.C
@@ -22,4 +22,10 @@ void foo ()
 
   pf = reinterpret_cast <PF>(po); // { dg-warning "8:casting between pointer-to-function and pointer-to-object is conditionally-supported" }
   po = reinterpret_cast <PO>(pf); // { dg-warning "8:casting between pointer-to-function and pointer-to-object is conditionally-supported" }
+
+  pf = __extension__ reinterpret_cast <PF>(pv);
+  pv = __extension__ reinterpret_cast <PV>(pf);
+
+  pf = __extension__ reinterpret_cast <PF>(po);
+  po = __extension__ reinterpret_cast <PO>(pf);
 }