Re: Difference between -O2 and -g

[Brian Wang <brian.wang.0721@gmail.com>]

On Fri, Oct 26, 2012 at 10:55 AM, Rich Felker <dalias@aerifal.cx> wrote:
> On Fri, Oct 26, 2012 at 10:47:57AM +0800, Brian Wang wrote:
>> On Fri, Oct 26, 2012 at 10:32 AM, Rich Felker <dalias@aerifal.cx> wrote:
>> > On Fri, Oct 26, 2012 at 10:04:46AM +0800, Brian Wang wrote:
>> >> > One very simple way to get a picture of what's going on in a program
>> >> > is to run it under strace. Try saving strace logs for both the working
>> >> > version and the broken version and comparing them either manually or
>> >> > with the diff utility (although the latter may be difficult unless you
>> >> > filter out the addresses and other contnets that will naturally
>> >> > differ, so it might be easier to visually inspect). If you don't
>> >> > already have an strace built for your target, I think Aboriginal Linux
>> >> > has static binaries you can use.
>> >>
>> >> I have previously built my static strace.
>> >> I could not decipher what went wrong.  Please find the strace logs for
>> >> the three binaries in question.
>> >> The source code is basically the same, except for the musl ones,
>> >> printf calls are sprinkled here and there
>> >> as my desperate attempt.
>> >
>> > The good and bad traces diverge at this line, which only happens in
>> > the good one:
>> >
>> > writev(2, [{"CreateColormap : good end\n", 26}, {NULL, 0}], 2) = 26
>> >
>> > So search the source for that string and see what condition is causing
>> > that code to be reached or not reached.
>>
>> Thank you for reading through them. :-)
>>
>> The failed call (XaceHook) is:
>> -----------
>>     /*
>>      * Security creation/labeling check
>>      */
>>     i = XaceHook(XACE_RESOURCE_ACCESS, clients[client], mid, RT_COLORMAP,
>>                pmap, RT_NONE, NULL, DixCreateAccess);
>>     if (i != Success) {
>>       fprintf(stderr, "%s : 9\n", __func__);
>>       FreeResource(mid, RT_NONE);
>>       return i;
>>     }
>> -----------
>
> It would help a lot if I knew what source you were using, or at least
> the part of the tree it corresponds to in the upstrea/latest X source
> tree, so I could take a look at it.

I am using a mildly patched one based on:
http://xorg.freedesktop.org/archive/individual/xserver/xorg-server-1.5.1.tar.bz2
The patch is about displaying a background ppm image and should be
after the error path.

The failed call is within dix/colormap.c:CreateColormap().

Thanks for helping.  I really appreciate it.


Brian

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