[Bug analyzer/109839] -Wanalyzer-fd-leak false positive with routine dup2

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109839

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |126830
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2026-08-13
             Status|UNCONFIRMED                 |NEW

--- Comment #2 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Here's another example that Claude Code generated for me:

$ cat t.c
#include <unistd.h>
#include <fcntl.h>

void redirect_stdout(const char *path)
{
  int fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
  if (fd < 0)
    return;

  int newfd = dup2(fd, STDOUT_FILENO);
  if (newfd < 0) {
    close(fd);
    return;
  }
  close(fd);
  /* newfd == STDOUT_FILENO == 1.  Stdout is intentionally left open,
     now redirected to path.  */
}

$ gcc -fanalyzer -c t.c
t.c: In function 'redirect_stdout':
t.c:17:1: warning: leak of file descriptor 'newfd' [-Wanalyzer-fd-leak]

https://godbolt.org/z/3vro6sKWr

Seen in the August 2026 OpenScanHub mass scan of Fedora 45 (PR 126830)
affecting json-c, audit/audispd, bash, and others (est. ~50-70 FPs).


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126830
[Bug 126830] Tracker bug for -fanalyzer false positives seen in August 2026
OpenScanHub mass scan