[Bug analyzer/109239] New: -Wanalyzer-deref-before-check seen on Linux kernel due to inlining with -fno-delete-null-pointer-checks

[Bug analyzer/109239] New: -Wanalyzer-deref-before-check seen on Linux kernel due to inlining with -fno-delete-null-pointer-checks

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109239

            Bug ID: 109239
           Summary: -Wanalyzer-deref-before-check seen on Linux kernel due
                    to inlining with -fno-delete-null-pointer-checks
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: analyzer
          Assignee: dmalcolm at gcc dot gnu.org
          Reporter: dmalcolm at gcc dot gnu.org
  Target Milestone: ---

Created attachment 54724
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54724&action=edit
Reproducer

I'm seeing various -Wanalyzer-deref-before-check false positives on the Linux
kernel; hopefully the attached is a representative reproducer for all of them.

When compiled with:
  -fanalyzer -fno-delete-null-pointer-checks -O2
trunk falsely complains:

In function 'bus_get',
    inlined from 'bus_remove_file' at <source>:122:7,
    inlined from 'remove_probe_files' at <source>:139:3,
    inlined from 'bus_unregister' at <source>:150:3:
<source>:105:6: warning: check of 'bus' for NULL after already dereferencing it
[-Wanalyzer-deref-before-check]
  105 |   if (bus) {
      |      ^
  'bus_unregister': events 1-2
    |
    |  147 |   if (bus->dev_root)
    |      |       ~~~^~~~~~~~~~
    |      |          |
    |      |          (1) pointer 'bus' is dereferenced here
    |......
    |  150 |   remove_probe_files(bus);
    |      |   ~       
    |      |   |
    |      |   (2) inlined call to 'remove_probe_files' from 'bus_unregister'
    |
    +--> 'remove_probe_files': event 3
           |
           |  139 |   bus_remove_file(bus, &bus_attr_drivers_autoprobe);
           |      |   ^
           |      |   |
           |      |   (3) inlined call to 'bus_remove_file' from
'remove_probe_files'
           |
           +--> 'bus_remove_file': event 4
                  |
                  |  122 |   if (bus_get(bus)) {
                  |      |       ^
                  |      |       |
                  |      |       (4) inlined call to 'bus_get' from
'bus_remove_file'
                  |
                  +--> 'bus_get': event 5
                         |
                         |  105 |   if (bus) {
                         |      |      ^
                         |      |      |
                         |      |      (5) pointer 'bus' is checked for NULL
here but it was already dereferenced at (1)
                         |
Compiler returned: 0

Trunk: https://godbolt.org/z/ErKf6fz86

[Bug analyzer/109239] -Wanalyzer-deref-before-check seen on Linux kernel due to inlining with -fno-delete-null-pointer-checks

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109239

--- Comment #1 from CVS 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:0c652ebbf79bd168766097f3ac4c1b3b79d68a43

commit r13-6800-g0c652ebbf79bd168766097f3ac4c1b3b79d68a43
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Wed Mar 22 08:40:34 2023 -0400

    analyzer: fix false +ves from -Wanalyzer-deref-before-check due to inlining
[PR109239]

    The patch has this effect on my integration tests of -fanalyzer:

      Comparison:
        GOOD: 129        (17.70% -> 17.92%)
         BAD: 600 -> 591 (-9)

    which is purely due to improvements to -Wanalyzer-deref-before-check
    on the Linux kernel:

      -Wanalyzer-deref-before-check:
        GOOD: 1        (4.55% -> 7.69%)
         BAD: 21 -> 12 (-9)
         Known false positives: 16 -> 10 (-6)
           linux-5.10.162: 7 -> 1 (-6)
         Suspected false positives: 3 -> 0 (-3)
           linux-5.10.162: 3 -> 0 (-3)

    gcc/analyzer/ChangeLog:
            PR analyzer/109239
            * program-point.cc: Include "analyzer/inlining-iterator.h".
            (program_point::effectively_intraprocedural_p): New function.
            * program-point.h (program_point::effectively_intraprocedural_p):
            New decl.
            * sm-malloc.cc (deref_before_check::emit): Use it when rejecting
            interprocedural cases, so that we reject interprocedural cases
            that have become intraprocedural due to inlining.

    gcc/testsuite/ChangeLog:
            PR analyzer/109239
            * gcc.dg/analyzer/deref-before-check-pr109239-linux-bus.c: New
test.

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

[Bug analyzer/109239] -Wanalyzer-deref-before-check seen on Linux kernel due to inlining with -fno-delete-null-pointer-checks

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109239

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

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

--- Comment #2 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Should be fixed by the above patch