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Subject: [Bug tree-optimization/80532] warning on pointer access after free
Date: Tue, 03 Nov 2020 04:11:16 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D80532

Eric Gallager <egallager at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |egallager at gcc dot gnu.o=
rg

--- Comment #4 from Eric Gallager <egallager at gcc dot gnu.org> ---
(In reply to David Malcolm from comment #3)
> My analyzer finds these:
>=20
> ./xgcc -B. -fanalyzer -c ../../src/gcc/testsuite/gcc.dg/analyzer/pr80532.c
> -ftime-report
> ../../src/gcc/testsuite/gcc.dg/analyzer/pr80532.c: In function =E2=80=98f=
ree_list=E2=80=99:
> ../../src/gcc/testsuite/gcc.dg/analyzer/pr80532.c:14:28: warning: use aft=
er
> =E2=80=98free=E2=80=99 of =E2=80=98p=E2=80=99 [CWE-416] [-Wanalyzer-use-a=
fter-free]
>    14 |   for (p =3D head; p !=3D 0; p =3D p->next) /* { dg-warning "use =
after
> 'free' of 'p'" } */
>       |                          ~~^~~~~~~~~
>   =E2=80=98free_list=E2=80=99: events 1-4
>     |
>     |   14 |   for (p =3D head; p !=3D 0; p =3D p->next) /* { dg-warning =
"use
> after 'free' of 'p'" } */
>     |      |   ^~~                    ~~~~~~~~~~~
>     |      |   |                        |
>     |      |   |                        (4) use after =E2=80=98free=E2=80=
=99 of =E2=80=98p=E2=80=99; freed
> at (3)
>     |      |   (1) following =E2=80=98true=E2=80=99 branch (when =E2=80=
=98p=E2=80=99 is non-NULL)...
>     |   15 |     free (p); /* { dg-message "freed here" } */
>     |      |     ~~~~~~~~
>     |      |     |
>     |      |     (2) ...to here
>     |      |     (3) freed here
>     |
> ../../src/gcc/testsuite/gcc.dg/analyzer/pr80532.c:14:28: note: 8 duplicat=
es
>    14 |   for (p =3D head; p !=3D 0; p =3D p->next) /* { dg-warning "use =
after
> 'free' of 'p'" } */
>       |                          ~~^~~~~~~~~
> ../../src/gcc/testsuite/gcc.dg/analyzer/pr80532.c: In function =E2=80=98f=
oobar=E2=80=99:
> ../../src/gcc/testsuite/gcc.dg/analyzer/pr80532.c:24:3: warning:
> double-=E2=80=98free=E2=80=99 of =E2=80=98p=E2=80=99 [CWE-415] [-Wanalyze=
r-double-free]
>    24 |   free (p); /* { dg-warning "double-'free' of 'p'" } */
>       |   ^~~~~~~~
>   =E2=80=98foobar=E2=80=99: events 1-2
>     |
>     |   22 |   memset (p, 0, n);
>     |      |   ^~~~~~~~~~~~~~~~
>     |      |   |
>     |      |   (1) first =E2=80=98free=E2=80=99 here
>     |   23 |   free (p); /* { dg-message "first 'free' here" } */
>     |   24 |   free (p); /* { dg-warning "double-'free' of 'p'" } */
>     |      |   ~~~~~~~~
>     |      |   |
>     |      |   (2) second =E2=80=98free=E2=80=99 here; first =E2=80=98fre=
e=E2=80=99 was at (1)
>     |

So... since the analyzer has been merged now... ok to close as FIXED?=