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Re: gmon.out creation procedure


Dear Shafi

Thanks you very much for the clear details. Definitely your inputs are
helpful.

1) I am sure that in gcc-4.0 I found there is file gmon.c in the path
gcc-4.0.0/gcc/gmon.c.  Anyhow let me concentrate on gmon.c of glibc.

2) Next thing I would like to know is to better understand the gmon.c of
glibc I would like to degug glibc. since glibc is linked with gcc, I built
gcc and glibc separately. while debugging gcc is referring shared glib
library, but not the one I built freshly for debugging purpose. To  make
this happen, where I need to change the path to like both gcc and glibc ?

3) Please correct me If I am wrong
   a. for every function mcount() function is called to collect the caller
and callee address. where this collected info is placed ?
   b. the flow of monstartup() function
                monstartup()-->moncontrol() --> profil()

      who will call the monstartup() ? is it gcrt0 ? before calling the
main() function of our routine ?

   c. write_profiling() --->  write_gmon() functions calls write_hist(),
write_call_graph() and write_bb_counts(). here who calls the
write_profiling() ?

   d. mcleanup() calls write_gmon(). who calls the mcleanup() ? is it
gcrt0 ? after control return from main() function ?

Thanks and Regards
Raja








> 2008/5/19  <raja.saleru@iap-online.com>:
>> Hi,
>>
>> I am Raja, I need a favor on understand how the gmon.out file is
>> created.
>> Please help me.
>>
>> 1. gmon.c is available in both gcc and glibc.  Which is the one used to
>> create gmon.out ?
>
> I don't think gcc has gmon.c. Only glibc has it. You can also find
> gmon in newlib for some targets. But this will be customized for the
> target
>
>>
>> 2. Can you brief how profile information required to create gmon.out is
>> captured?&#65533;&#65533;&#65533;"B"BWhich are the functions are
responsible for this ?
>
> These days gmon.c is used only to get histogram records(time related
> infomation). All the other information is now produced by gcc itself,
> than can be analyzed using gcov. (You will get gcov when you build
> gcc).
> For histogram records, gmon.c code primarily uses 'profil' system
> call. You can get more information about this in man pages. And of
> course you will get to know how this is used if you go through the
> code in gmon.c
>
> When -pg switch is enabled all complier does is inserting a call to
> the function mcount, usually after the function prologue. This is the
> function the collects all the needed information. For profiling
> information about caller address and callee address is necessary. If
> this information cannot be obtained using __bultin_return_address then
> this is calculated by mcount in a target specific manner and passed
> onto another function that takes these address as the arguments and
> gathers the profiling information.
>
>>
>> 3. Suppose assume that executable is built without &#65533;&#65533;Cpg
option, but
>> want
>> to create gmon.out at run-time. Is there any way or guidelines to
>> implement?
>
> A call to the profiling function (mcount) should be there to generate
> profiling information. Without that you won't be able to generate
> gmon.out
>
> Hope this helps,
>
> Regards,
> Shafi
>
>>
>> Thanks and Regards
>> Raja Saleru
>>
>>
>


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