[Bug other/109163] SARIF (and other JSON) output files are non-deterministic

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109163

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by David Malcolm <dmalcolm@gcc.gnu.org>:

https://gcc.gnu.org/g:7f1e15f743357e037d7c4f6f6000863c26f3dfc3

commit r13-6851-g7f1e15f743357e037d7c4f6f6000863c26f3dfc3
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Fri Mar 24 11:38:14 2023 -0400

    json: preserve key-insertion order [PR109163]

    PR other/109163 notes that when we write out JSON files, we traverse
    the keys within each object via hash_map iteration, and thus the
    ordering is non-deterministic - it can arbitrarily vary from run to
    run and from different machines, making it harder for users to compare
    results and determine if anything has "really" changed.

    I'm running into this issue with SARIF output, but there are several
    places where we're currently emitting JSON:

      * -fsave-optimization-record emits SRCFILE.opt-record.json.gz
            "This option is experimental and the format of the data within
            the compressed JSON file is subject to change."; see
            optinfo-emit-json.{h,cc}, dumpfile.cc, etc
      * -fdiagnostics-format= with the various "sarif" and "json" options
      * -fdump-analyzer-json is a developer option in the analyzer
      * gcov has:
         "-j, --json-format: Output JSON intermediate format into
         .gcov.json.gz file"

    This patch adds an auto_vec to class json::object to preserve
    key-insertion order, and use it when writing out objects.  Potentially
    this slightly slows down JSON output, but I believe that this isn't
    normally a bottleneck, and that the benefits to the user of
    deterministic output are worth it.

    I had first attempted to use ordered_hash_map.h for this, but ran into
    impenetrable template errors, so this patch uses a simpler approach of
    just adding an auto_vec to json::object.

    Testing showed a failure of diagnostic-format-json-5.c, which was using
    a convoluted set of regexps to consume the output; I believe that this
    was brittle, and was intermittently failing for some of the random
    orderings of output.  I rewrote these regexps to work with the expected
    output order.  The other such tests seem to pass with the
    now-deterministic orderings.

    gcc/ChangeLog:
            PR other/109163
            * json.cc: Update comments to indicate that we now preserve
            insertion order of keys within objects.
            (object::print): Traverse keys in insertion order.
            (object::set): Preserve insertion order of keys.
            (selftest::test_writing_objects): Add an additional key to verify
            that we preserve insertion order.
            * json.h (object::m_keys): New field.

    gcc/testsuite/ChangeLog:
            PR other/109163
            * c-c++-common/diagnostic-format-json-1.c: Update comment.
            * c-c++-common/diagnostic-format-json-2.c: Likewise.
            * c-c++-common/diagnostic-format-json-3.c: Likewise.
            * c-c++-common/diagnostic-format-json-4.c: Likewise.
            * c-c++-common/diagnostic-format-json-5.c: Rewrite regexps.
            * c-c++-common/diagnostic-format-json-stderr-1.c: Update comment.

    Signed-off-by: David Malcolm <dmalcolm@redhat.com>