PROBLEM: getpid() returning same value as getppid()

["Sébastien Paumier" <sebastien.paumier@univ-mlv.fr>]

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Hi,
here is a bug that occurs on my kernel 2.6.31-21, maybe with older ones. 
  If a C program contains a function with the constructor attribute that 
calls getpid(), then, a call to syscall(SYS_fork) produces a son that 
obtains the same value calling getpid() or getppid().

Best regards,
Sébastien Paumier

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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <sys/types.h>

void foo(void) __attribute__ ((constructor));

void foo(void) {
	/* Removing this call to getpid() removes the bug */
	getpid();
}


int main(void){
	int i=syscall(SYS_fork);
	if (0==i) 
		/* Big problem: the son prints the same value for getpid() and getppid() */
		printf("__son : %d   father : %d__\n", getpid(), getppid());
	else
		printf("<<father : %d   son : %d>>\n", getpid(), i);
	return 0;
}