[Bug jit/63854] Fix memory leaks seen in JIT

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63854

--- Comment #33 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Alex Coplan <acoplan@gcc.gnu.org>:

https://gcc.gnu.org/g:b46584d7836bee011facdf946fd7241c748d66f0

commit r11-2799-gb46584d7836bee011facdf946fd7241c748d66f0
Author: Alex Coplan <alex.coplan@arm.com>
Date:   Fri Aug 21 14:26:11 2020 +0100

    driver: Fix several memory leaks [PR63854]

    This patch fixes several memory leaks in the driver, all of which relate
    to the handling of static specs. We introduce functions
    set_static_spec_{shared,owned}() which are used to enforce proper memory
    management when updating the strings in the static_specs table.

    This is achieved by making use of the alloc_p field in the table
    entries. Similarly to set_spec(), each time we update an entry, we check
    whether alloc_p is set, and free the old value if so. We then set
    alloc_p correctly based on whether we "own" this memory or whether we're
    just taking a pointer to a shared string which we shouldn't free.

    The following table shows the number of leaks found by AddressSanitizer
    when running a minimal libgccjit program on AArch64. The test program
    does the whole libgccjit compilation cycle in a loop (including acquiring
    and releasing the context), and the table below shows the number of leaks
    for different iterations of that loop.

    +--------------+-----+-----+------+---------------+
    | # of runs >  | 1   | 2   | 3    | Leaks per run |
    +--------------+-----+-----+------+---------------+
    | Before patch | 463 | 940 | 1417 | 477           |
    +--------------+-----+-----+------+---------------+
    | After patch  | 416 | 846 | 1276 | 430           |
    +--------------+-----+-----+------+---------------+

    gcc/ChangeLog:

            PR jit/63854
            * gcc.c (set_static_spec): New.
            (set_static_spec_owned): New.
            (set_static_spec_shared): New.
            (driver::maybe_putenv_COLLECT_LTO_WRAPPER): Use
            set_static_spec_owned() to take ownership of lto_wrapper_file
            such that it gets freed in driver::finalize.
            (driver::maybe_run_linker): Use set_static_spec_shared() to
            ensure that we don't try and free() the static string "ld",
            also ensuring that any previously-allocated string in
            linker_name_spec is freed. Likewise with argv0.
            (driver::finalize): Use set_static_spec_shared() when resetting
            specs that previously had allocated strings; remove if(0)
            around call to free().