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Re: Bizarre GCC problem - how do I debug it?


On 08/06/10 10:24, David Daney wrote:
> On 08/06/2010 10:19 AM, Bruce Korb wrote:
>> The problem seems to be that GDB thinks all the code belongs to a
>> single line of text.  At first, it was a file of mine, so I presumed
>> I had done something strange and passed it off.  I needed to do some
>> more debugging again and my "-g -O0" output still said all code
>> belonged to that one line.  So, I made a .i file and compiled that.
>> Different file, but the same problem.  The .i file contains the
>> correct preprocessor directives:
>>
>>    # 309 "wrapup.c"
>>    static void
>>    done_check(void)
>>    {
>>
>> but under gdb:
>>
>>    (gdb) b done_check
>>    Breakpoint 5 at 0x40af44: file /usr/include/gmp.h, line 1661.
>>
>> the break point *is* on the entry to "done_check", but the
>> source code displayed is line 1661 of gmp.h.  Not helpful.
>> Further, I cannot set break points on line numbers because
>> all code belongs to the one line in gmp.h.
>>
>> Yes, for now I can debug in assembly code, but it isn't very easy.....
>>
>> $ gcc --version
>> gcc (SUSE Linux) 4.5.0 20100604 [gcc-4_5-branch revision 160292]
>> Copyright (C) 2010 Free Software Foundation, Inc.
>> This is free software; see the source for copying conditions.  There
>> is NO
>> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
>> PURPOSE.
>>
>> I've googled for:  gcc|gdb wrong source file
>> which only yields how to examine source files in gdb.
>>
> 
> Which version of GDB?
> 
> IIRC with GCC-4.5 you need a very new version of GDB.  This page:
> 
> http://gcc.gnu.org/gcc-4.5/changes.html
> 
> indicates that GDB 7.0 or later would be good candidates.

That seems to work.  There are one or two or three bugs then.
Either gdb needs to recognize an out of sync object code, or else
gcc needs to produce object code that forces gdb to object in a way
more obvious than just deciding upon the wrong file and line --
or both.  I simply installed the latest openSuSE and got whatever
was supplied.  It isn't reasonable to expect folks to go traipsing
through upstream web sites looking for "changes.html" files ....

And, of course, the insight stuff needs to incorporate the latest
and greatest gdb.  (I don't use ddd because it is _completely_ non-
intuitive.)


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