[Bug libc/18023] extend_alloca is broken (questionable pointer comparison, horrible machine code)

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18023

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=43b1048ab9418e902aac8c834a7a9a88c501620a

commit 43b1048ab9418e902aac8c834a7a9a88c501620a
Author: Florian Weimer <fweimer@redhat.com>
Date:   Mon Jun 25 19:29:11 2018 +0200

    nss_files: Use struct scratch_buffer instead of extend_alloca [BZ #18023]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=1599ed4e959e6e5b319d82389667f51d01d53da0

commit 1599ed4e959e6e5b319d82389667f51d01d53da0
Author: Florian Weimer <fweimer@redhat.com>
Date:   Mon Jun 25 19:22:46 2018 +0200

    getent: Use dynarray in initgroups_keys [BZ #18023]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=a26fe1638bf2fea58ddd44cc771896ad0c36de8c

commit a26fe1638bf2fea58ddd44cc771896ad0c36de8c
Author: Florian Weimer <fweimer@redhat.com>
Date:   Mon Jun 25 19:14:09 2018 +0200

    _nss_nis_initgroups_dyn: Use struct scratch_buffer [BZ #18023]

    Remove extend_alloca usage.  Also adjusts the internal function get_uid.

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=90d9d9ce2fbeef0f24a957efa83f5a78367a84d4

commit 90d9d9ce2fbeef0f24a957efa83f5a78367a84d4
Author: Florian Weimer <fweimer@redhat.com>
Date:   Mon Jun 25 18:56:42 2018 +0200

    getgrent_next_nss (compat-initgroups): Remove alloca fallback [BZ #18023]

    If the caller-supplied buffer is not large enough, fall back directly
    malloc.

    The previous __libc_use_alloca check was incorrect because it did not
    take into account that extend_alloca may fail to merge allocations, so
    it would underestimate the stack space being used by roughly a factor
    of two.

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                          |   24 ++++++++++++++++++
 nis/nss_nis/nis-initgroups.c       |   27 +++++++++++++--------
 nss/getent.c                       |   40 +++++++++++++++++++++++--------
 nss/nss_compat/compat-initgroups.c |   46 ++++++++++++++++-------------------
 nss/nss_files/files-initgroups.c   |   32 ++++++++-----------------
 5 files changed, 102 insertions(+), 67 deletions(-)

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