[4.2] PR32102 -Wall stomps on -Wstrict-overflow and -Wstrict-aliasing

["Manuel López-Ibáñez" <lopezibanez at gmail dot com>]

This patch prevents -Wall from overriding the value of an explicit
-Wstrict-overflow option (similarly for -Wstrict-aliasing).

Bootstrapped with --enable-languages=all --disable-multilib
and regression tested on x86_64-unknown-linux-gnu

OK to commit to 4.2 branch?


2008-01-24  Manuel Lopez-Ibanez <manu@gcc.gnu.org>

  PR 32102
  * flags.h (warn_strict_aliasing): Remove.
  (warn_strict_overflow): Remove.
  * opts.c (warn_strict_aliasing): Remove.
  (warn_strict_overflow): Remove.
  * c-opts.c (c_common_handle_option): -Wall only sets
-Wstrict-aliasing or -Wstrict-overflow if they are uninitialized.
  (c_common_post_options): Give default values to -Wstrict-aliasing
and -Wstrict-overflow if they are uninitialized.
  * common.opt (Wstrict-aliasing): Specify Var and Init.
  (Wstrict-overflow): Likewise.

testsuite/
  * gcc.dg/Wstrict-overflow-21.c: New.
  * g++.dg/warn/Wstrict-aliasing-8.C: New.

Index: gcc/flags.h
===================================================================
--- gcc/flags.h	(revision 131745)
+++ gcc/flags.h	(working copy)
@@ -106,20 +106,10 @@ extern void set_Wunused (int setting);
    values are larger than N bytes. The value N is in `larger_than_size'.  */
 
 extern bool warn_larger_than;
 extern HOST_WIDE_INT larger_than_size;
 
-/* Nonzero means warn about constructs which might not be strict
-   aliasing safe.  */
-
-extern int warn_strict_aliasing;
-
-/* Nonzero means warn about optimizations which rely on undefined
-   signed overflow.  */
-
-extern int warn_strict_overflow;
-
 /* Temporarily suppress certain warnings.
    This is set while reading code from a system header file.  */
 
 extern int in_system_header;
 
Index: gcc/testsuite/gcc.dg/Wstrict-overflow-21.c
===================================================================
--- gcc/testsuite/gcc.dg/Wstrict-overflow-21.c	(revision 0)
+++ gcc/testsuite/gcc.dg/Wstrict-overflow-21.c	(revision 0)
@@ -0,0 +1,10 @@
+/* PR 32102: -Wall stomps on -Wstrict-overflow */
+/* { dg-do compile } */
+/* { dg-options "-fstrict-overflow -O2 -Wstrict-overflow=2 -Wall" } */
+int
+foo (int i)
+{
+  return __builtin_abs (i) >= 0; /* { dg-warning "assuming signed overflow does not occur" "correct warning" } */
+}
+
+
Index: gcc/testsuite/g++.dg/warn/Wstrict-aliasing-8.C
===================================================================
--- gcc/testsuite/g++.dg/warn/Wstrict-aliasing-8.C	(revision 0)
+++ gcc/testsuite/g++.dg/warn/Wstrict-aliasing-8.C	(revision 0)
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-Wstrict-aliasing=2 -O2 -Wall" } */
+
+int a[2];
+
+double *foo1(void)
+{
+  return (double *)a; /* { dg-warning "strict-aliasing" } */
+}
+
+double *foo2(void)
+{
+  return (double *)&a[0]; /* { dg-warning "strict-aliasing" } */
+}
+
+__complex__ double x;
+int *bar(void)
+{
+  return (int *)&__imag__ x; /* { dg-warning "strict-aliasing" } */
+}
Index: gcc/opts.c
===================================================================
--- gcc/opts.c	(revision 131745)
+++ gcc/opts.c	(working copy)
@@ -54,18 +54,10 @@ bool extra_warnings;
    than N bytes.  Also want about function definitions whose returned
    values are larger than N bytes, where N is `larger_than_size'.  */
 bool warn_larger_than;
 HOST_WIDE_INT larger_than_size;
 
-/* Nonzero means warn about constructs which might not be
-   strict-aliasing safe.  */
-int warn_strict_aliasing;
-
-/* Nonzero means warn about optimizations which rely on undefined
-   signed overflow.  */
-int warn_strict_overflow;
-
 /* Hack for cooperation between set_Wunused and set_Wextra.  */
 static bool maybe_warn_unused_parameter;
 
 /* Type(s) of debugging information we are producing (if any).  See
    flags.h for the definitions of the different possible types of
Index: gcc/c-opts.c
===================================================================
--- gcc/c-opts.c	(revision 131745)
+++ gcc/c-opts.c	(working copy)
@@ -1,7 +1,7 @@
 /* C/ObjC/C++ command line option handling.
-   Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007
+   Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008
    Free Software Foundation, Inc.
    Contributed by Neil Booth.
 
 This file is part of GCC.
 
@@ -390,12 +390,14 @@ c_common_handle_option (size_t scode, co
       warn_return_type = value;
       warn_sequence_point = value;	/* Was C only.  */
       if (c_dialect_cxx ())
 	warn_sign_compare = value;
       warn_switch = value;
-      warn_strict_aliasing = value;
-      warn_strict_overflow = value;
+      if (warn_strict_aliasing == -1)
+	warn_strict_aliasing = value;
+      if (warn_strict_overflow == -1)
+	warn_strict_overflow = value;
       warn_address = value;
 
       /* Only warn about unknown pragmas that are not in system
 	 headers.  */
       warn_unknown_pragmas = value;
@@ -1034,10 +1036,15 @@ c_common_post_options (const char **pfil
   /* -Wpointer_sign is disabled by default, but it is enabled if any
      of -Wall or -pedantic are given.  */
   if (warn_pointer_sign == -1)
     warn_pointer_sign = 0;
 
+  if (warn_strict_aliasing == -1)
+    warn_strict_aliasing = 0;
+  if (warn_strict_overflow == -1)
+    warn_strict_overflow = 0;
+
   /* -Woverlength-strings is off by default, but is enabled by -pedantic.
      It is never enabled in C++, as the minimum limit is not normative
      in that standard.  */
   if (warn_overlength_strings == -1 || c_dialect_cxx ())
     warn_overlength_strings = 0;
Index: gcc/common.opt
===================================================================
--- gcc/common.opt	(revision 131745)
+++ gcc/common.opt	(working copy)
@@ -127,19 +127,19 @@ Warn when not issuing stack smashing pro
 Wstrict-aliasing
 Common
 Warn about code which might break strict aliasing rules
 
 Wstrict-aliasing=
-Common Joined UInteger
+Common Joined UInteger Var(warn_strict_aliasing) Init(-1)
 Warn about code which might break strict aliasing rules
 
 Wstrict-overflow
 Common
 Warn about optimizations that assume that signed overflow is undefined
 
 Wstrict-overflow=
-Common Joined UInteger
+Common Joined UInteger Var(warn_strict_overflow) Init(-1)
 Warn about optimizations that assume that signed overflow is undefined
 
 Wswitch
 Common Var(warn_switch)
 Warn about enumerated switches, with no default, missing a case