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Commit 0444aa9c by Nathan Sidwell Committed by Nathan Sidwell
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[PR c/84293] Unexpected strict-alias warning 

https://gcc.gnu.org/ml/gcc-patches/2018-02/msg00510.html
	PR c/84293
	gcc/c/
	* c-typeck.c (build_indirect_ref, build_c_cast): Pass expr location
	to strict_aliasing_warning.

	gcc/c-family/
	* c-common.h (strict_aliasing_warning): Drop OTYPE arg, insert LOC
	arg.
	* c-warn.c (strict_aliasing_warning): Drop OTYPE arg, require LOC
	arg.  Adjust.

	gcc/cp/
	* typeck.c (cp_build_indirect_ref_1, build_reinterpret_cast_1):
	Pass expr location to strict_aliasing_warning.

	gcc/testsuite/
	* c-c++-common/pr84293.h: New.
	* c-c++-common/pr84293.c: New.

From-SVN: r257539
parent dd2799cc
Showing with 72 additions and 25 deletions
gcc/c-family/ChangeLog
2018-02-09 Nathan Sidwell <nathan@acm.org>
PR c/84293
* c-common.h (strict_aliasing_warning): Drop OTYPE arg, insert LOC
arg.
* c-warn.c (strict_aliasing_warning): Drop OTYPE arg, require LOC
arg. Adjust.
2018-02-09 Martin Sebor <msebor@redhat.com>
PR lto/84212
......
gcc/c-family/c-common.h
......@@ -1260,7 +1260,7 @@ extern void warn_tautological_cmp (location_t, enum tree_code, tree, tree);
extern void warn_logical_not_parentheses (location_t, enum tree_code, tree,
tree);
extern bool warn_if_unused_value (const_tree, location_t);
extern bool strict_aliasing_warning (tree, tree, tree);
extern bool strict_aliasing_warning (location_t, tree, tree);
extern void sizeof_pointer_memaccess_warning (location_t *, tree,
vec<tree, va_gc> *, tree *,
bool (*) (tree, tree));
......
gcc/c-family/c-warn.c
......@@ -599,17 +599,21 @@ warn_if_unused_value (const_tree exp, location_t locus)
}
}
/* Print a warning about casts that might indicate violation
of strict aliasing rules if -Wstrict-aliasing is used and
strict aliasing mode is in effect. OTYPE is the original
TREE_TYPE of EXPR, and TYPE the type we're casting to. */
/* Print a warning about casts that might indicate violation of strict
aliasing rules if -Wstrict-aliasing is used and strict aliasing
mode is in effect. LOC is the location of the expression being
cast, EXPR might be from inside it. TYPE is the type we're casting
to. */
bool
strict_aliasing_warning (tree otype, tree type, tree expr)
strict_aliasing_warning (location_t loc, tree type, tree expr)
{
if (loc == UNKNOWN_LOCATION)
loc = input_location;
/* Strip pointer conversion chains and get to the correct original type. */
STRIP_NOPS (expr);
otype = TREE_TYPE (expr);
tree otype = TREE_TYPE (expr);
if (!(flag_strict_aliasing
&& POINTER_TYPE_P (type)
......@@ -628,8 +632,9 @@ strict_aliasing_warning (tree otype, tree type, tree expr)
if the cast breaks type based aliasing. */
if (!COMPLETE_TYPE_P (TREE_TYPE (type)) && warn_strict_aliasing == 2)
{
warning (OPT_Wstrict_aliasing, "type-punning to incomplete type "
"might break strict-aliasing rules");
warning_at (loc, OPT_Wstrict_aliasing,
"type-punning to incomplete type "
"might break strict-aliasing rules");
return true;
}
else
......@@ -645,15 +650,17 @@ strict_aliasing_warning (tree otype, tree type, tree expr)
&& !alias_set_subset_of (set2, set1)
&& !alias_sets_conflict_p (set1, set2))
{
warning (OPT_Wstrict_aliasing, "dereferencing type-punned "
"pointer will break strict-aliasing rules");
warning_at (loc, OPT_Wstrict_aliasing,
"dereferencing type-punned "
"pointer will break strict-aliasing rules");
return true;
}
else if (warn_strict_aliasing == 2
&& !alias_sets_must_conflict_p (set1, set2))
{
warning (OPT_Wstrict_aliasing, "dereferencing type-punned "
"pointer might break strict-aliasing rules");
warning_at (loc, OPT_Wstrict_aliasing,
"dereferencing type-punned "
"pointer might break strict-aliasing rules");
return true;
}
}
......@@ -669,8 +676,9 @@ strict_aliasing_warning (tree otype, tree type, tree expr)
if (!COMPLETE_TYPE_P (type)
|| !alias_sets_must_conflict_p (set1, set2))
{
warning (OPT_Wstrict_aliasing, "dereferencing type-punned "
"pointer might break strict-aliasing rules");
warning_at (loc, OPT_Wstrict_aliasing,
"dereferencing type-punned "
"pointer might break strict-aliasing rules");
return true;
}
}
......
gcc/c/ChangeLog
2018-02-09 Nathan Sidwell <nathan@acm.org>
PR c/84293
* c-typeck.c (build_indirect_ref, build_c_cast): Pass expr location
to strict_aliasing_warning.
2018-02-02 Paolo Carlini <paolo.carlini@oracle.com>
* c-typeck.c (really_start_incremental_init, push_init_level,
......
gcc/c/c-typeck.c
......@@ -2524,7 +2524,7 @@ build_indirect_ref (location_t loc, tree ptr, ref_operator errstring)
the backend. This only needs to be done at
warn_strict_aliasing > 2. */
if (warn_strict_aliasing > 2)
if (strict_aliasing_warning (TREE_TYPE (TREE_OPERAND (pointer, 0)),
if (strict_aliasing_warning (EXPR_LOCATION (pointer),
type, TREE_OPERAND (pointer, 0)))
TREE_NO_WARNING (pointer) = 1;
}
......@@ -5696,7 +5696,7 @@ build_c_cast (location_t loc, tree type, tree expr)
"of different size");
if (warn_strict_aliasing <= 2)
strict_aliasing_warning (otype, type, expr);
strict_aliasing_warning (EXPR_LOCATION (value), type, expr);
/* If pedantic, warn for conversions between function and object
pointer types, except for converting a null pointer constant
......
gcc/cp/ChangeLog
2018-02-09 Nathan Sidwell <nathan@acm.org>
PR c/84293
* typeck.c (cp_build_indirect_ref_1, build_reinterpret_cast_1):
Pass expr location to strict_aliasing_warning.
2018-02-09 Jason Merrill <jason@redhat.com>
PR c++/84296 - ICE with qualified-id in template.
......
gcc/cp/typeck.c
......@@ -3136,7 +3136,7 @@ cp_build_indirect_ref_1 (tree ptr, ref_operator errorstring,
the backend. This only needs to be done at
warn_strict_aliasing > 2. */
if (warn_strict_aliasing > 2)
if (strict_aliasing_warning (TREE_TYPE (TREE_OPERAND (ptr, 0)),
if (strict_aliasing_warning (EXPR_LOCATION (ptr),
type, TREE_OPERAND (ptr, 0)))
TREE_NO_WARNING (ptr) = 1;
}
......@@ -7334,7 +7334,7 @@ build_reinterpret_cast_1 (tree type, tree expr, bool c_cast_p,
expr = cp_build_addr_expr (expr, complain);
if (warn_strict_aliasing > 2)
strict_aliasing_warning (TREE_TYPE (expr), type, expr);
strict_aliasing_warning (EXPR_LOCATION (expr), type, expr);
if (expr != error_mark_node)
expr = build_reinterpret_cast_1
......@@ -7428,8 +7428,6 @@ build_reinterpret_cast_1 (tree type, tree expr, bool c_cast_p,
else if ((TYPE_PTRDATAMEM_P (type) && TYPE_PTRDATAMEM_P (intype))
|| (TYPE_PTROBV_P (type) && TYPE_PTROBV_P (intype)))
{
tree sexpr = expr;
if (!c_cast_p
&& check_for_casting_away_constness (intype, type,
REINTERPRET_CAST_EXPR,
......@@ -7447,11 +7445,9 @@ build_reinterpret_cast_1 (tree type, tree expr, bool c_cast_p,
warning (OPT_Wcast_align, "cast from %qH to %qI "
"increases required alignment of target type", intype, type);
/* We need to strip nops here, because the front end likes to
create (int *)&a for array-to-pointer decay, instead of &a[0]. */
STRIP_NOPS (sexpr);
if (warn_strict_aliasing <= 2)
strict_aliasing_warning (intype, type, sexpr);
/* strict_aliasing_warning STRIP_NOPs its expr. */
strict_aliasing_warning (EXPR_LOCATION (expr), type, expr);
return build_nop (type, expr);
}
......
gcc/testsuite/ChangeLog
2018-02-09 Nathan Sidwell <nathan@acm.org>
PR c/84293
* c-c++-common/pr84293.h: New.
* c-c++-common/pr84293.c: New.
2018-02-09 Vladimir Makarov <vmakarov@redhat.com>
PR rtl-optimization/57193
......
gcc/testsuite/c-c++-common/pr84293.c 0 → 100644
/* PR c/84293 unexpected warning from system header. */
#include "./pr84293.h"
struct typeobject thing;
#pragma GCC diagnostic warning "-Wstrict-aliasing"
void __attribute__ ((optimize (2))) init ()
{
INCREF_TDEF (&thing);
INCREF_STAG (&thing);
}
gcc/testsuite/c-c++-common/pr84293.h 0 → 100644
/* PR c/84293 unexpected warning from system header expansion. */
#pragma GCC system_header
struct typeobject { unsigned refs; };
typedef struct object { unsigned refs; } Object;
#define INCREF_TDEF(op) (((Object*)(op))->refs++)
#define INCREF_STAG(op) (((struct object*)(op))->refs++)
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