[Bug c/94641] New: -Wpadded -fsanitize=undefined together cause warning on main()

[Bug c/94641] New: -Wpadded -fsanitize=undefined together cause warning on main()

[edgardragon444 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94641

            Bug ID: 94641
           Summary: -Wpadded -fsanitize=undefined together cause warning
                    on main()
           Product: gcc
           Version: 9.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: edgardragon444 at gmail dot com
  Target Milestone: ---

Hi, as I'm fiddling with warning flags (yep, synthesizing -Weverything, what
could go wrong?)

The '-fsanitize=undefined' causes the '-Wpadded' to misbehave, telling me
 'main()' struct size is being padded. Disabling UBsan silences the warning.

Happens when all three are true:
1. -fsanitize=undefined flag specified
2. -Wpadded flag specified
3. printf() used

Maybe dup of bug 68901, yet that's c++ with function nested within a struct.
I'm C, and only have printf(). 

Seen on 8.3.0, 9.2.0 and trunk (https://godbolt.org/z/jFSPf_).
> ed@Fold ~ $ (gcc -xc /dev/fd/9 -Wpadded -fsanitize=address -o /dev/null)9<<<$'#include <stdio.h>\nint main() {printf("Hi"); return 0;}'
> ed@Fold ~ $ (gcc -xc /dev/fd/9 -Wpadded -fsanitize=undefined -o /dev/null)9<<<$'#include <stdio.h>\nint main() {printf("Hi"); return 0;}'
> /dev/fd/9: In function ‘main’:
> /dev/fd/9:2:1: warning: padding struct size to alignment boundary [-Wpadded]
>     2 | int main() {printf("Hi"); return 0;}
>       | ^~~
> ed@Fold ~ $ (gcc -xc /dev/fd/9 -Wpadded -fsanitize=undefined -o /dev/null)9<<<$'#include <stdio.h>\nint main() {return 0;}'
> ed@Fold ~ $ gcc -v
> Using built-in specs.
> COLLECT_GCC=gcc
> COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/9.2.0/lto-wrapper
> Target: x86_64-pc-linux-gnu
> Configured with: /tmp/portage/portage/sys-devel/gcc-9.2.0-r4/work/gcc-9.2.0/configure --host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/9.2.0 --includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include --datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/9.2.0 --mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/9.2.0/man --infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/9.2.0/info --with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include/g++-v9 --with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/9.2.0/python --enable-languages=c,c++,fortran --enable-obsolete --enable-secureplt --disable-werror --with-system-zlib --enable-nls --without-included-gettext --enable-checking=release --with-bugurl=https://bugs.gentoo.org/ --with-pkgversion='Gentoo 9.2.0-r4 p5' --disable-esp --enable-libstdcxx-time --with-build-config=bootstrap-lto --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu --enable-multilib --with-multilib-list=m32,m64 --disable-altivec --disable-fixed-point --enable-targets=all --enable-libgomp --disable-libmudflap --disable-libssp --disable-systemtap --enable-vtable-verify --enable-lto --with-isl --disable-isl-version-check --enable-default-pie --enable-default-ssp
> Thread model: posix
> gcc version 9.2.0 (Gentoo 9.2.0-r4 p5)
> ed@Fold ~ $

[Bug c/94641] -Wpadded -fsanitize=undefined together cause warning on main()

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94641

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
                 CC|                            |marxin at gcc dot gnu.org
   Last reconfirmed|                            |2020-04-20

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
Confirmed, started with GCC 5.1.0.

[Bug c/94641] -Wpadded -fsanitize=undefined together cause warning on main()

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94641

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|                            |jakub at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |jakub at gcc dot gnu.org

[Bug c/94641] -Wpadded -fsanitize=undefined together cause warning on main()

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94641

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 48310
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48310&action=edit
gcc10-pr94641.patch

Untested fix.

[Bug c/94641] -Wpadded -fsanitize=undefined together cause warning on main()

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94641

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:73f8e9dca5ff891ed19001b213fd1f6ce31417e3

commit r10-7849-g73f8e9dca5ff891ed19001b213fd1f6ce31417e3
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Tue Apr 21 17:06:31 2020 +0200

    ubsan: Avoid -Wpadded warnings [PR94641]

    -Wpadded warnings aren't really useful for the artificial types that GCC
    lays out for ubsan.

    2020-04-21  Jakub Jelinek  <jakub@redhat.com>

            PR c/94641
            * stor-layout.c (place_field, finalize_record_size): Don't emit
            -Wpadded warning on TYPE_ARTIFICIAL rli->t.
            * ubsan.c (ubsan_get_type_descriptor_type,
            ubsan_get_source_location_type, ubsan_create_data): Set
            TYPE_ARTIFICIAL.
            * asan.c (asan_global_struct): Likewise.

            * c-c++-common/ubsan/pr94641.c: New test.

[Bug c/94641] -Wpadded -fsanitize=undefined together cause warning on main()

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94641

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed on the trunk so far.

[Bug c/94641] -Wpadded -fsanitize=undefined together cause warning on main()

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94641

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-9 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:1e4a928134e8f17bbcae99f2bac2bbce73ef6f73

commit r9-8882-g1e4a928134e8f17bbcae99f2bac2bbce73ef6f73
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Tue Apr 21 17:06:31 2020 +0200

    ubsan: Avoid -Wpadded warnings [PR94641]

    -Wpadded warnings aren't really useful for the artificial types that GCC
    lays out for ubsan.

    2020-04-21  Jakub Jelinek  <jakub@redhat.com>

            PR c/94641
            * stor-layout.c (place_field, finalize_record_size): Don't emit
            -Wpadded warning on TYPE_ARTIFICIAL rli->t.
            * ubsan.c (ubsan_get_type_descriptor_type,
            ubsan_get_source_location_type, ubsan_create_data): Set
            TYPE_ARTIFICIAL.
            * asan.c (asan_global_struct): Likewise.

            * c-c++-common/ubsan/pr94641.c: New test.

    (cherry picked from commit 73f8e9dca5ff891ed19001b213fd1f6ce31417e3)

[Bug c/94641] -Wpadded -fsanitize=undefined together cause warning on main()

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94641

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

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

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed for 8.5 in r8-10489-g3e8a10bb21b4c830e1884ff43edd639eae5bf5ce and by the
above commit for 9.4+ too.