linking with __CTOR_LIST__

Abby abs621@yahoo.com
Tue Sep 12 16:51:00 GMT 2006


Hi,

Thanks Ravi,
I am using default linker script. ld -verbose.
which already has folloing section..

  .ctors          :
  {
    /* gcc uses crtbegin.o to find the start of
       the constructors, so we make sure it is
       first.  Because this is a wildcard, it
       doesn't matter if the user does not
       actually link against crtbegin.o; the
       linker won't look for a file to match a
       wildcard.  The wildcard also means that it
       doesn't matter which directory crtbegin.o
       is in.  */
    KEEP (*crtbegin*.o(.ctors))
    /* We don't want to include the .ctor section from
       from the crtend.o file until after the sorted ctors.
       The .ctor section from the crtend file contains the
       end of ctors marker and it must be last */
    KEEP (*(EXCLUDE_FILE (*crtend*.o ) .ctors))
    KEEP (*(SORT(.ctors.*)))
    KEEP (*(.ctors))
  }

you mean i can just append following line to the above lines
(sorry for asking all from you guys - still learning).

__CTOR_LIST__ = ADDR(.ctors)


Regards,
Abby.


Ravishankar S-2 wrote:
> 
> Hi,
> 
> It may be possible to do this with the linker. The constructors are
> allocatted to the .ctors section in the final ELF file.
> 
> Just add this in your linker script:
> 
> .ctors 
> {
>   *(.ctors);
> }
> 
> __CTOR_LIST__ = ADDR(.ctors)
> 
> Caveat: I have not tried this !
> 
> Regards,
> Ravishankar
> 
> 
> 
> -----Original Message-----
> From: gcc-help-owner@gcc.gnu.org [mailto:gcc-help-owner@gcc.gnu.org] On
> Behalf Of Abby
> Sent: Tuesday, September 12, 2006 3:48 PM
> To: gcc-help@gcc.gnu.org
> Subject: Re: linking with __CTOR_LIST__
> 
> 
> 
> Hi Grig,
> 
> thanks for reply. there must be some way to walk and call those
> pointers? want to do something like as follows on linux appllication. 
> 
> To use gcov for a application which runs all the time, i wanted to
> change the behavior.
> 
> This is the code extract from
> http://lwn.net/2002/0207/a/gcov-kernel.php3
> 
> extern long __CTOR_LIST__;
> typedef void (*func_ptr)(void) ;
> func_ptr *p = (func_ptr*) &__CTOR_LIST__;
> 
> if ( p == NULL) {
> printk("No CTORS\n");
> return;
> }
> for ( ; *p != (func_ptr) 0; p++) {
> (*p) ();
> }
> 
> I wanted to do similar stuff for the application.
> Any other idea or right alias (if it is not the one).
> 
> thanks and regards,
> abby.
> 
> 
> Grigory Zagorodnev wrote:
>> 
>> Abby wrote:
>>> i am writing an application (linux) where i am trying to reference 
>>> __CTOR_LIST__ ?
>>> /tmp/cc2rTvyB.o(.data+0x0): undefined reference to `__CTOR_LIST__'
>>> 
>>> any idea?
>>> abby.
>> 
>> __CTOR_LIST__ is a local symbol, it can't be referenced from outside
>> crtbegin*.o startup object file.
>> 
>> - Grigory
>> 
>> 
> 
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> 
> 
> 

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