On Tue, Jul 7, 2015 at 2:42 AM, Prathamesh Kulkarni
<prathamesh.kulka...@linaro.org> wrote:
> On 6 July 2015 at 12:00, Richard Biener <richard.guent...@gmail.com> wrote:
>> On Sun, Jul 5, 2015 at 2:07 PM, Prathamesh Kulkarni
>> <prathamesh.kulka...@linaro.org> wrote:
>>> Hi,
>>> Passing -dx causes segmentation fault:
>>> Test case: void f(void) {}
>>>
>>> ./test.c: In function 'f':
>>> ../test.c:3:1: internal compiler error: Segmentation fault
>>> }
>>> ^
>>> 0xab6baf crash_signal
>>> /home/prathamesh.kulkarni/gnu-toolchain/src/gcc.git/gcc/toplev.c:366
>>> 0x694b14 verify_flow_info()
>>>
>>> /home/prathamesh.kulkarni/gnu-toolchain/src/gcc.git/gcc/cfghooks.c:109
>>> 0x9f7e64 execute_function_todo
>>>
>>> /home/prathamesh.kulkarni/gnu-toolchain/src/gcc.git/gcc/passes.c:1997
>>> 0x9f86eb execute_todo
>>>
>>> /home/prathamesh.kulkarni/gnu-toolchain/src/gcc.git/gcc/passes.c:2042
>>>
>>> Started with r210068.
>>> It looks like -dx causes cfun->cfg to be NULL, and hence the segfault
>>> in verify_flow_info().
>>> The attached patch tries to fix it by adding a check to cfun->cfg before
>>> calling
>>> verify_flow_info() from execute_function_todo().
>>> Bootstrapped and tested on x86_64-unknown-linux-gnu.
>>> OK for trunk ?
>>
>> No. We've checked cfun->curr_properties & PROP_cfg already. So whatever
>> is keeping that set but frees the CFG is the offender (and should
>> clear the flag).
> I think I have somewhat understood what's happening.
> -dx turns on flag rtl_dump_and_exit.
> pass_rest_of_compilation is gated on !rtl_dump_and_exit.
> Since rtl_dump_and_exit == 1 when -dx is passed,
> pass_rest_of_compilation and all the
> rtl passes inserted within pass_rest_of_compilation don't execute.
> One of these passes is pass_free_cfg which destorys PROP_cfg, but with
> -dx passed,
> this pass doesn't get executed and PROP_cfg remains set.
> Then pass_clean_state::execute() calls free_after_compilation(), which
> sets cfun->cfg = NULL.
> And hence after pass_clean_state finishes in execute_function_todo, we
> end up with cfun->cfg == NULL and CFG_prop set,
> which calls verify_flow_info() and we hit the segfault.
>
> The following untested patch tries to fix this by clearing CFG_prop in
> free_after_compilation.
> Shall that be correct approach ?
Yes, that looks good to me.
Richard.
> Thanks,
> Prathamesh
>>
>> Richard.
>>
>>> Thank you,
>>> Prathamesh
