[PATCH] driver: Fix several memory leaks

Alex Coplan Alex.Coplan@arm.com
Mon Aug 3 15:01:46 GMT 2020


Ping.

> -----Original Message-----
> From: Jit <jit-bounces@gcc.gnu.org> On Behalf Of Alex Coplan
> Sent: 14 July 2020 10:08
> To: gcc-patches@gcc.gnu.org; jit@gcc.gnu.org
> Subject: [PATCH] driver: Fix several memory leaks
> 
> Updating the subject since this is really just a driver change (and
> therefore needs a review from those who can approve patches there).
> 
> Thanks,
> Alex
> 
> -----Original Message-----
> From: Jit <jit-bounces@gcc.gnu.org> On Behalf Of Alex Coplan
> Sent: 09 July 2020 21:13
> To: gcc-patches@gcc.gnu.org; jit@gcc.gnu.org
> Cc: nd <nd@arm.com>
> Subject: [PATCH] libgccjit: Fix several memory leaks in the driver
> 
> Hello,
> 
> 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           |
> +--------------+-----+-----+------+---------------+
> 
> Ensuring that we minimize "leaks per run" (ultimately eliminating all of
> them) is important in order for long-running applications to be able to
> make use of in-process libgccjit.
> 
> Testing:
>  * Bootstrap and regtest on aarch64-linxu-gnu, x86_64-linux-gnu.
>  * Bootstrap and regtest on aarch64-linux-gnu with bootstrap-asan config.
>  * Smoke test of libgccjit, ran regressions on a --disable-bootstrap
> build on
>    aarch64-linux-gnu.
> 
> OK for master?
> 
> Thanks,
> Alex
> 
> ---
> 
> gcc/ChangeLog:
> 
> 2020-07-09  Alex Coplan  <alex.coplan@arm.com>
> 
> 	* 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().



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