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From: Edek <edek.pieITAKNIECZYTAM@gmail.com>
Newsgroups: comp.lang.c++
Subject: Re: efficient function call
Date: Fri, 27 May 2011 16:39:05 +0200
Organization: ATMAN - ATM S.A.
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.c++:5703


> So you're saying a file
>
>    static int foo() { return 42; }
>    int bar() { return 69+foo(); }
>
> will never inline foo() if I use g++ with the -fpic option?
> That sounds wrong -- and I cannot repeat it on my system.
>
> tuva:/tmp>  g++ -W -Wall -ansi -fpic -O3 -c foo.cc
> tuva:/tmp>  nm -C foo.o
> 00000000 V DW.ref.__gxx_personality_v0
> 00000000 T bar()
>           U __gxx_personality_v0
>

To check that I am not lying to you:
------------------------------------------------------
int answer () { return 42; };

int bar () { return 69|answer(); }
-------------------------------------------------
gcc -O3 -S test.cpp

	.type	_Z3barv, @function
_Z3barv:
.LFB1:
	.cfi_startproc
	movl	$111, %eax
	ret
------------------------------------------------------
gcc -O3 -S -fPIC test.cpp

	.type	_Z3barv, @function
_Z3barv:
.LFB1:
	.cfi_startproc
	subq	$8, %rsp
	.cfi_def_cfa_offset 16
	call	_Z6answerv@PLT
	addq	$8, %rsp
	.cfi_def_cfa_offset 8
	orl	$69, %eax
	ret

And the working thing:
-------------------------------------------------------------------------
  [devel@marvin preload]$ LD_LIBRARY_PATH=. ./main
bar gives111
  [devel@marvin preload]$ LD_LIBRARY_PATH=. LD_PRELOAD=./mylib.so ./main
bar gives1093
  [devel@marvin preload]$
----------------------------------------------------------------------

where main is

#include <iostream>

extern int bar();

int main () {
     std::cout << "bar gives" << bar () <<std::endl;
}

Edek