[Bug middle-end/13421] IA32 bigmem pointer subtraction and –ftrapv option causes unjustified program abort

[Bug middle-end/13421] IA32 bigmem pointer subtraction and –ftrapv option causes unjustified program abort

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=13421

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |oss at malat dot biz

--- Comment #15 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 81801 has been marked as a duplicate of this bug. ***

[Bug middle-end/13421] IA32 bigmem pointer subtraction and –ftrapv option causes unjustified program abort

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=13421

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |baiwfg2 at gmail dot com

--- Comment #16 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 110399 has been marked as a duplicate of this bug. ***

[Bug middle-end/13421] IA32 bigmem pointer subtraction and –ftrapv option causes unjustified program abort

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=13421

--- Comment #17 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:667c19de86b33648f5f4599f589a5e02adbb35cb

commit r15-67-g667c19de86b33648f5f4599f589a5e02adbb35cb
Author: Richard Biener <rguenther@suse.de>
Date:   Tue Apr 16 14:05:35 2024 +0200

    middle-end/13421 - -ftrapv vs. POINTER_DIFF_EXPR

    Currently we expand POINTER_DIFF_EXPR using subv_optab when -ftrapv
    (but -fsanitize=undefined does nothing).  That's not consistent
    with the behavior of POINTER_PLUS_EXPR which never uses addv_optab
    with -ftrapv.  Both are because of the way we select whether to use
    the trapping or the non-trapping optab - we look at the result type
    of the expression and check

      trapv = INTEGRAL_TYPE_P (type) && TYPE_OVERFLOW_TRAPS (type);

    the bugreport correctly complains that -ftrapv affects pointer
    subtraction (there's no -ftrapv-pointer).  Now that we have
    POINTER_DIFF_EXPR we can honor that appropriately.

    The patch moves both POINTER_DIFF_EXPR and POINTER_PLUS_EXPR
    handling so they will never consider trapping (or saturating)
    optabs.

            PR middle-end/13421
            * optabs-tree.cc (optab_for_tree_code): Do not consider
            {add,sub}v or {us,ss}{add,sub} optabs for POINTER_DIFF_EXPR
            or POINTER_PLUS_EXPR.

[Bug middle-end/13421] IA32 bigmem pointer subtraction and –ftrapv option causes unjustified program abort

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=13421

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |15.0
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #18 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed for GCC 15.

[Bug middle-end/13421] IA32 bigmem pointer subtraction and –ftrapv option causes unjustified program abort

[eggert at twinsun dot com]

------- Additional Comments From eggert at twinsun dot com  2004-04-06 05:13 -------
A point of clarification: even if pointers are changed to be consistently
unsigned internally (which seems to be the right thing to do, if pointer
comparison is unsigned), GCC must still check for overflow when subtracting
pointers. For example, suppose we have the 2 GiB array "a" successfully
allocated by "char *a = malloc (1u<<31);". Then the expression "(a + (1u<<31)) -
a" is of type ptrdiff_t, which is a signed 32-bit integer that cannot represent
(1u<<31). So this expression must generate a trap with -ftrapv, regardless of
whether pointers are unsigned internally.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13421