[Bug tree-optimization/102919] New: spurious -Wrestrict warning for sprintf into the same member array as argument plus offset

[Bug tree-optimization/102919] New: spurious -Wrestrict warning for sprintf into the same member array as argument plus offset

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102919

            Bug ID: 102919
           Summary: spurious -Wrestrict warning for sprintf into the same
                    member array as argument plus offset
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

The write below by sprintf into p->a cannot overlap with the read from p->a + 2
because the length of the string at p->a + 2 is at most 1.  The only it might
overlap is if the string was longer than fits in the array which would make the
sprintf call invalid for another reason: reading past the end.  The -Wrestrict
instance should be avoided here.

$ cat z.c && gcc -O2 -S -Wall z.c
struct A { char a[4]; int i; };

void f (struct A *p)
{ 
  __builtin_sprintf (p->a, "%s", p->a + 2);
}
z.c: In function ‘void f(A*)’:
z.c:5:21: warning: ‘__builtin_sprintf’ argument 3 may overlap destination
object ‘p’ [-Wrestrict]
    5 |   __builtin_sprintf (p->a, "%s", p->a + 2);
      |   ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
z.c:3:19: note: destination object referenced by ‘restrict’-qualified argument
1 was declared here
    3 | void f (struct A *p)
      |         ~~~~~~~~~~^

[Bug tree-optimization/102919] spurious -Wrestrict warning for sprintf into the same member array as argument plus offset

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102919

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
             Blocks|                            |84774
   Last reconfirmed|                            |2021-10-24
           Keywords|                            |diagnostic
           Assignee|unassigned at gcc dot gnu.org      |msebor at gcc dot gnu.org


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84774
[Bug 84774] [meta-bug] bogus/missing -Wrestrict

[Bug tree-optimization/102919] spurious -Wrestrict warning for sprintf into the same member array as argument plus offset

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102919

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch
   Target Milestone|---                         |12.0

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
Patch: https://gcc.gnu.org/pipermail/gcc-patches/2021-October/582446.html

[Bug tree-optimization/102919] spurious -Wrestrict warning for sprintf into the same member array as argument plus offset

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102919

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Martin Sebor <msebor@gcc.gnu.org>:

https://gcc.gnu.org/g:1ff4dbddcf74203a1e16316b18e12f9e1b5085f0

commit r12-4727-g1ff4dbddcf74203a1e16316b18e12f9e1b5085f0
Author: Martin Sebor <msebor@redhat.com>
Date:   Tue Oct 26 14:40:33 2021 -0600

    Improve/correct detection of overlapping aggregates [PR102238, PR102919].

    Resolves:
    PR tree-optimization/102238 - alias_offset in gimple-ssa-sprintf.c is
broken
    PR tree-optimization/102919 - spurious -Wrestrict warning for sprintf into
the same member array as argument plus offset

    gcc/ChangeLog:

            PR tree-optimization/102238
            PR tree-optimization/102919
            * gimple-ssa-sprintf.c (get_string_length): Add an argument.
            (array_elt_at_offset): Move to pointer-query.
            (set_aggregate_size_and_offset): New function.
            (field_at_offset):  Move to pointer-query.
            (get_origin_and_offset): Rename...
            (get_origin_and_offset_r): this.  Add an argument.  Make aggregate
            handling more robust.
            (get_origin_and_offset): New.
            (alias_offset): Add an argument.
            (format_string): Use subobject size determined by
get_origin_and_offset.
            * pointer-query.cc (field_at_offset): Move from
gimple-ssa-sprintf.c.
            Improve/correct handling of aggregates.
            (array_elt_at_offset): Same.
            * pointer-query.h (field_at_offset): Declare.
            (array_elt_at_offset): Declare.

    gcc/testsuite/ChangeLog:

            PR tree-optimization/102238
            PR tree-optimization/102919
            * gcc.dg/tree-ssa/builtin-sprintf-warn-23.c: Remove warnings.
            * gcc.dg/Wrestrict-23.c: New test.

[Bug tree-optimization/102919] spurious -Wrestrict warning for sprintf into the same member array as argument plus offset

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102919

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
Done r12-4727.