[Bug analyzer/109106] New: GCC Static Analyzer doesn't model printf

[Bug analyzer/109106] New: GCC Static Analyzer doesn't model printf

[geoffreydgr at icloud dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109106

            Bug ID: 109106
           Summary: GCC Static Analyzer doesn't model printf
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: analyzer
          Assignee: dmalcolm at gcc dot gnu.org
          Reporter: geoffreydgr at icloud dot com
  Target Milestone: ---

GCC Static Analyzer does not model `printf`.

see it live: https://godbolt.org/z/6ooW44sPq

Input:
```c
#include <stdio.h>

int main() { 
  int *j = 0;
  printf("NPD_FLAG\n") || *j;
}
```

Output:
```
<source>: In function 'main':
<source>:10:27: warning: dereference of NULL 'j' [CWE-476]
[-Wanalyzer-null-dereference]
   10 |   printf("NPD_FLAG\n") || *j;
      |                           ^~
  'main': events 1-4
    |
    |    9 |   int *j = 0;
    |      |        ^
    |      |        |
    |      |        (1) 'j' is NULL
    |   10 |   printf("NPD_FLAG\n") || *j;
    |      |   ~~~~~~~~~~~~~~~~~~~~~~~~~~
    |      |                        |  |
    |      |                        |  (3) ...to here
    |      |                        |  (4) dereference of NULL 'j'
    |      |                        (2) following 'false' branch...
    |
Compiler returned: 0
```

[Bug analyzer/109106] GCC Static Analyzer doesn't model printf

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109106

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
printf can still return 0.

[Bug analyzer/109106] GCC Static Analyzer doesn't model printf

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109106

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Why do you think printf will not return zero in some cases? Especially if
stdout is write fails.

[Bug analyzer/109106] GCC Static Analyzer doesn't model printf

[schwab@linux-m68k.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109106

--- Comment #3 from Andreas Schwab <schwab@linux-m68k.org> ---
When an output error occurs it returns < 0.  Only printf("") or printf("%s",
"") can return 0.

[Bug analyzer/109106] GCC Static Analyzer doesn't model printf

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109106

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

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

--- Comment #4 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Thanks for filing this, and for the comments; marking it as a dup of PR 107017

*** This bug has been marked as a duplicate of bug 107017 ***

[Bug analyzer/109106] GCC Static Analyzer doesn't model printf

[geoffreydgr at icloud dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109106

--- Comment #5 from Geoffrey <geoffreydgr at icloud dot com> ---
(In reply to David Malcolm from comment #4)
> Thanks for filing this, and for the comments; marking it as a dup of PR
> 107017
> 
> *** This bug has been marked as a duplicate of bug 107017 ***

Hi, David. I want to ask a question that does GSA supports printf now?

The gcc online docs
(https://gcc.gnu.org/onlinedocs/gcc/Static-Analyzer-Options.html#index-fanalyzer-checker)
says that GSA has hardcoded knowledge about the behavior of this function. But
I find that GSA still cannot handle printf (see
https://godbolt.org/z/6ooW44sPq). Then I checked the source code, I find that
you have modeled `sprintf`. 
I am wondering why GCC static analysis misses `printf`. IMO, it seems
straightforward to model. Or actually it is hard to model?