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From: "contino at epigenesys dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug analyzer/105906] New: fanalyzer strdup false positive leak in
 loop
Date: Thu, 09 Jun 2022 09:33:01 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105906

            Bug ID: 105906
           Summary: fanalyzer strdup false positive leak in loop
           Product: gcc
           Version: 12.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: analyzer
          Assignee: dmalcolm at gcc dot gnu.org
          Reporter: contino at epigenesys dot com
  Target Milestone: ---

Created attachment 53109
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D53109&action=3Dedit
The warning

Hi,
compiling the code with GCC-12.1.0 on Debian I am seeing the fanalyzer warn=
ing
in the attachment, which seems to me a false positive leak related to strdu=
p.

Code:

#include <stddef.h>
#include <stdlib.h>
#include <string.h>

#define LEN 64

char **__epystr_explode(const char *delim, char *str)
{
        char **out =3D NULL;
        int i;

        if (str =3D=3D NULL || delim =3D=3D NULL)
                return NULL;

        out =3D malloc(LEN * sizeof(char *));
        if (out =3D=3D NULL)
                return NULL;

        for (i =3D 0; i < LEN; i++) {
                out[i] =3D strdup("bla");
                if (out[i] =3D=3D NULL)
                        goto freem;
        }
        return out;

freem:
        while (--i >=3D 0)
                free(out[i]);
        free(out);
        return NULL;
}

If I replace strdup with malloc the warning disappears.

for (i =3D 0; i < LEN; i++) {
        out[i] =3D malloc(10);
        if (out[i] =3D=3D NULL)
                goto freem;
}

The same happens if I replace the for loop with a goto loop.

i =3D 0;
loop:
out[i] =3D strdup("bla");
if (out[i] =3D=3D NULL)
        goto freem;
i++
if (i < LEN)
        goto loop;=