re PR c/25509 (can't disable __attribute__((warn_unused_result)))

2009-07-10  Manuel López-Ibáñez  <manu@gcc.gnu.org>

	PR 25509
	PR 40614
	* c.opt (Wunused-result): New.
	* doc/invoke.texi: Document it.
	* c-common.c (c_warn_unused_result): Use it.
testsuite/
	* g++.dg/warn/unused-result1-Werror.c: New.

From-SVN: r149458

gcc/ChangeLog

@@ -1,3 +1,11 @@
+2009-07-10  Manuel López-Ibáñez  <manu@gcc.gnu.org>
+
+	PR 25509
+	PR 40614
+	* c.opt (Wunused-result): New.
+	* doc/invoke.texi: Document it.
+	* c-common.c (c_warn_unused_result): Use it.
+
 2009-07-09  DJ Delorie  <dj@redhat.com>
 
 	* targhooks.c (default_target_can_inline_p): Rename from

gcc/c-common.c

@@ -8266,11 +8266,13 @@ c_warn_unused_result (gimple_seq seq)
 	      location_t loc = gimple_location (g);
 
 	      if (fdecl)
-		warning_at (loc, 0, "ignoring return value of %qD, "
+		warning_at (loc, OPT_Wunused_result, 
+			    "ignoring return value of %qD, "
 			    "declared with attribute warn_unused_result",
 			    fdecl);
 	      else
-		warning_at (loc, 0, "ignoring return value of function "
+		warning_at (loc, OPT_Wunused_result,
+			    "ignoring return value of function "
 			    "declared with attribute warn_unused_result");
 	    }
 	  break;

gcc/c.opt

@@ -488,6 +488,10 @@ Wunused-macros
 C ObjC C++ ObjC++ Warning
 Warn about macros defined in the main file that are not used
 
+Wunused-result
+C ObjC C++ ObjC++ Var(warn_unused_result) Init(1) Warning
+Warn if a caller of a function, marked with attribute warn_unused_result, does not use its return value
+
 Wvariadic-macros
 C ObjC C++ ObjC++ Warning
 Do not warn about using variadic macros when -pedantic

gcc/doc/invoke.texi

@@ -260,7 +260,7 @@ Objective-C and Objective-C++ Dialects}.
 -Wsystem-headers  -Wtrigraphs  -Wtype-limits  -Wundef  -Wuninitialized @gol
 -Wunknown-pragmas  -Wno-pragmas -Wunreachable-code @gol
 -Wunsuffixed-float-constants  -Wunused  -Wunused-function @gol
--Wunused-label  -Wunused-parameter  -Wunused-value  -Wunused-variable @gol
+-Wunused-label  -Wunused-parameter -Wno-unused-result -Wunused-value  -Wunused-variable @gol
 -Wvariadic-macros -Wvla @gol
 -Wvolatile-register-var  -Wwrite-strings}
 
@@ -3259,6 +3259,13 @@ Warn whenever a function parameter is unused aside from its declaration.
 To suppress this warning use the @samp{unused} attribute
 (@pxref{Variable Attributes}).
 
+@item -Wno-unused-result
+@opindex Wunused-result
+@opindex Wno-unused-result
+Do not warn if a caller of a function marked with attribute
+@code{warn_unused_result} (@pxref{Variable Attributes}) does not use
+its return value. The default is @option{-Wunused-result}.
+
 @item -Wunused-variable
 @opindex Wunused-variable
 @opindex Wno-unused-variable

gcc/testsuite/ChangeLog

@@ -1,3 +1,9 @@
+2009-07-10  Manuel López-Ibáñez  <manu@gcc.gnu.org>
+
+	PR 25509
+	PR 40614
+	* g++.dg/warn/unused-result1-Werror.c: New.
+
 2009-07-10  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/39334

gcc/testsuite/g++.dg/warn/unused-result1-Werror.c

@@ -0,0 +1,10 @@
+// PR 40614
+// { dg-options "-Werror=unused-result" }
+class QByteArray {
+public:
+  QByteArray(const QByteArray &);
+};
+class QString {
+  QByteArray toLocal8Bit() const __attribute__ ((warn_unused_result));
+  void fooWarnHere() const { toLocal8Bit(); } // { dg-error "ignoring" }
+};