Bug gives no stack trace on segfault

Bug gives no stack trace on segfault

[nick]

Greetings,

I've been busy so this probably has been fixed in since I last worked on it:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88395

I was using these instructions to try and get a trace:
https://www.gnu.org/software/gcc/bugs/segfault.html

But nothing seems to be outputted and don't known if that's normal. Here is what I'm
running the program with and I've enabled --enable-checking:

gdb --args ./bin/g++  -v -da -Q -fconcepts test.cpp 

Cheers,

Nick

Re: Bug gives no stack trace on segfault

[Jonathan Wakely]

On Sun, 17 Mar 2019, 00:21 nick, <xerofoify@gmail.com> wrote:

> Greetings,
>
> I've been busy so this probably has been fixed in since I last worked on
> it:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88395
>
> I was using these instructions to try and get a trace:
> https://www.gnu.org/software/gcc/bugs/segfault.html
>
> But nothing seems to be outputted and don't known if that's normal. Here
> is what I'm
> running the program with and I've enabled --enable-checking:
>
> gdb --args ./bin/g++  -v -da -Q -fconcepts test.cpp
>

That is not what the instructions you linked to tell you to do.

You need to run that command to find out how the g++ driver invokes the
cc1plus compiler, and then debug cc1plus, not g++.

Re: Bug gives no stack trace on segfault

[nick]

On 2019-03-17 6:50 a.m., Jonathan Wakely wrote:
> On Sun, 17 Mar 2019, 00:21 nick, <xerofoify@gmail.com> wrote:
> 
>> Greetings,
>>
>> I've been busy so this probably has been fixed in since I last worked on
>> it:
>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88395
>>
>> I was using these instructions to try and get a trace:
>> https://www.gnu.org/software/gcc/bugs/segfault.html
>>
>> But nothing seems to be outputted and don't known if that's normal. Here
>> is what I'm
>> running the program with and I've enabled --enable-checking:
>>
>> gdb --args ./bin/g++  -v -da -Q -fconcepts test.cpp
>>
> 
> That is not what the instructions you linked to tell you to do.
> 
> You need to run that command to find out how the g++ driver invokes the
> cc1plus compiler, and then debug cc1plus, not g++.
> 

Jonathan,

Thanks I wasn't running them correctly it seems. I'm wondering after tracing it as this looks
very odd to me but does this:

if (tree prev = lookup_concept_satisfaction (tmpl, targs))        
	return prev;  

on line 2044 in gcc/cp/constraint.cc return a NULL_TREE if it's no found as that seems to
be the case in the bug as it's the one place that is mostly after a very brief look
at for the segfault. 

Nick