[Bug bootstrap/80047] fixincludes/fixincl.c: PVS-Studio: Improper Release of Memory Before Removing Last Reference (CWE-401)

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80047

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Xi Ruoyao <xry111@gcc.gnu.org>:

https://gcc.gnu.org/g:04c5a91d068c4ca2f09c2bc206fce00db9d1790b

commit r12-5234-g04c5a91d068c4ca2f09c2bc206fce00db9d1790b
Author: Xi Ruoyao <xry111@mengyan1223.wang>
Date:   Tue Nov 9 21:40:04 2021 +0800

    fixincludes: simplify handling for access() failure [PR21283, PR80047]

    POSIX says:

        On some implementations, if buf is a null pointer, getcwd() may obtain
        size bytes of memory using malloc(). In this case, the pointer returned
        by getcwd() may be used as the argument in a subsequent call to free().
        Invoking getcwd() with buf as a null pointer is not recommended in
        conforming applications.

    This produces an error building GCC with --enable-werror-always:

        ../../../fixincludes/fixincl.c: In function âprocessâ:
        ../../../fixincludes/fixincl.c:1356:7: error: argument 1 is null but
        the corresponding size argument 2 value is 4096 [-Werror=nonnull]

    It's suggested by POSIX to call getcwd() with progressively larger
    buffers until it does not give an [ERANGE] error. However, it's highly
    unlikely that this error-handling route is ever used.

    So we can simplify it instead of writting too much code.  We give up to
    use getcwd(), because `make` will output a `Leaving directory ...` message
    containing the path to cwd when we call abort().

    fixincludes/ChangeLog:

            PR other/21823
            PR bootstrap/80047
            * fixincl.c (process): Simplify the handling for highly
              unlikely access() failure, to avoid using non-standard
              extensions.