Re: How to troubleshoot a crash under Cygwin at -O3?

[Jeffrey Walton <noloader at gmail dot com>]

On Wed, Aug 12, 2015 at 5:31 AM, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> On 12 August 2015 at 10:22, Jonathan Wakely wrote:
>> On 12 August 2015 at 00:03, Jeffrey Walton wrote:
>>>
>>> *If* I force -fPIC on the command line and endure 135 or so of these:
>>>
>>>     $ make
>>>     g++ -DNDEBUG -g -O3 -fPIC -march=native -pipe -c shacal2.cpp
>>>     shacal2.cpp:1:0: warning: -fPIC ignored for target (all code is
>>> position independent)
>>>     // shacal2.cpp - by Kevin Springle, 2003
>>>     ^
>>>
>>> Then the program executes fine. But its a very messy compile, and its
>>> probably not going to be worth forcing -fPIC because we will get too
>>> much negative feedback.
>>
>> This doesn't make any sense. If -fPIC is ignored then how does addng
>> it make any difference?
>>
>> Have you compared the object files with and without -fPIC to see if it
>> does make any difference? If it does, there shouldn't be a warning
>> about ignoring it.
>
> Looking at the code for Cysgin it looks like for 64-bit -fpic is
> always used, so if you use -fPIC you get a warning, but -fpic would
> not get a warning. Adding -fPIC should not affect codegen, because
> with or without it you get -fpic. For 32-bit adding either -fpic or
> -fPIC gives a warning, but should not affect codegen.

I think you might be right here. I think I was working it with as
order-of-initialization problem, and I did add init_priority to try
and tame the issue.

Let me try to isolate it further in a cleaner room.

(And I know this is a horrible, open ended question. Sorry about the
question. I'm trying to figure out how to get a toehold into the
problem).

Jeff