[Bug analyzer/110520] New: -Wanalyzer-null-dereference false nagetive with `*ptr = 10086`

[Bug analyzer/110520] New: -Wanalyzer-null-dereference false nagetive with `*ptr = 10086`

[dale.mengli.ming at proton dot me]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110520

            Bug ID: 110520
           Summary: -Wanalyzer-null-dereference false nagetive with `*ptr
                    = 10086`
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: analyzer
          Assignee: dmalcolm at gcc dot gnu.org
          Reporter: dale.mengli.ming at proton dot me
  Target Milestone: ---

Hi,in this case (https://godbolt.org/z/4Md3o94Gx), the `ptr` is a null pointer,
but the analyzer doesn't report an NPD with it. When `__builtin_strlen(buf) ==
0` (https://godbolt.org/z/fnbMY9W5z), the analyzer reports that.

[Bug analyzer/110520] -Wanalyzer-null-dereference false nagetive with `*ptr = 10086`

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110520

David Malcolm <dmalcolm at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2023-09-06

--- Comment #1 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Thanks for filing this bug.

With trunk (for gcc 14) I correctly get a NPD warning (true positive):
  https://godbolt.org/z/a5h38cz7d

With gcc 13.2, I don't (false negative):
  https://godbolt.org/z/PKnToYK8v

I've been rewriting C string handling for gcc 14, so it's likely this now
working is a side-effect of that.

Keeping open to track adding a regression test for this.

[Bug analyzer/110520] -Wanalyzer-null-dereference false nagetive with `*ptr = 10086`

[dale.mengli.ming at proton dot me]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110520

--- Comment #2 from mengli ming <dale.mengli.ming at proton dot me> ---
(In reply to David Malcolm from comment #1)
> Thanks for filing this bug.
> 
> With trunk (for gcc 14) I correctly get a NPD warning (true positive):
>   https://godbolt.org/z/a5h38cz7d
> 
> With gcc 13.2, I don't (false negative):
>   https://godbolt.org/z/PKnToYK8v
> 
> I've been rewriting C string handling for gcc 14, so it's likely this now
> working is a side-effect of that.
> 
> Keeping open to track adding a regression test for this.

Thank you for your explanation. (^_^)

[Bug analyzer/110520] -Wanalyzer-null-dereference false negative with `*ptr = 10086`

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110520

--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by David Malcolm <dmalcolm@gcc.gnu.org>:

https://gcc.gnu.org/g:eb37ea529745c38dcf86c3cdbedb66df69ea9e35

commit r14-9075-geb37ea529745c38dcf86c3cdbedb66df69ea9e35
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Mon Feb 19 18:07:59 2024 -0500

    analyzer, testsuite: add regression test [PR110520]

    gcc/testsuite/ChangeLog:
            PR analyzer/110520
            * c-c++-common/analyzer/null-deref-pr110520.c: New test.

    Signed-off-by: David Malcolm <dmalcolm@redhat.com>

[Bug analyzer/110520] -Wanalyzer-null-dereference false negative with `*ptr = 10086`

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110520

David Malcolm <dmalcolm at gcc dot gnu.org> changed:

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

--- Comment #4 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
(In reply to David Malcolm from comment #1)
> Keeping open to track adding a regression test for this.

Regression test added; closing.