[Bug analyzer/104370] New: False positive from -Wanalyzer-mismatching-deallocation with reallocarray

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104370

            Bug ID: 104370
           Summary: False positive from
                    -Wanalyzer-mismatching-deallocation with reallocarray
           Product: gcc
           Version: 12.0
            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 52344
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52344&action=edit
Reduced reproducer

>From downstream report here:
  https://bugzilla.redhat.com/show_bug.cgi?id=2047926#c0

Compiling the attachment with -fanalyzer gives:

<source>: In function 'main':
<source>:21:15: warning: 'foo' should have been deallocated with 'free' but was
deallocated with 'reallocarray' [CWE-762] [-Wanalyzer-mismatching-deallocation]
   21 |     new_foo = reallocarray(foo, 201, 200);
      |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~
  'main': events 1-5
    |
    |   17 |     foo = calloc(200, 200);
    |      |           ^~~~~~~~~~~~~~~~
    |      |           |
    |      |           (1) allocated here (expects deallocation with 'free')
    |   18 |     if (!foo)
    |      |        ~   
    |      |        |
    |      |        (2) assuming 'foo' is non-NULL
    |      |        (3) following 'false' branch (when 'foo' is non-NULL)...
    |......
    |   21 |     new_foo = reallocarray(foo, 201, 200);
    |      |               ~~~~~~~~~~~~~~~~~~~~~~~~~~~
    |      |               |
    |      |               (4) ...to here
    |      |               (5) deallocated with 'reallocarray' here; allocation
at (1) expects deallocation with 'free'
    |

Compiler Explorer:
  https://godbolt.org/z/K7xaxrfcs

Recent glibc headers declare reallocarray twice, with different attributes:
 
https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=c1760eaf3b575ad174fd88b252fd16bd525fa818