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instruction: 0.439
runtime: 0.384
syscall: 0.177
riscv32 user mode emulation: fork return values broken
When running in a chroot with riscv32 (on x86_64; qemu git master as of today):
The following short program forks; the child immediately returns with exit(42). The parent checks for the return value - and obtains 40!
gcc-10.2
===============================================
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/wait.h>
main(c, v)
int c;
char **v;
{
pid_t pid, p;
int s, i, n;
s = 0;
pid = fork();
if (pid == 0)
exit(42);
/* wait for the process */
p = wait(&s);
if (p != pid)
exit (255);
if (WIFEXITED(s))
{
int r=WEXITSTATUS(s);
if (r!=42) {
printf("child wants to return %i (0x%X), parent received %i (0x%X), difference %i\n",42,42,r,r,r-42);
}
}
}
===============================================
(riscv-ilp32 chroot) farino /tmp # ./wait-test-short
child wants to return 42 (0x2A), parent received 40 (0x28), difference -2
===============================================
(riscv-ilp32 chroot) farino /tmp # gcc --version
gcc (Gentoo 10.2.0-r1 p2) 10.2.0
Copyright (C) 2020 Free Software Foundation, Inc.
Dies ist freie Software; die Kopierbedingungen stehen in den Quellen. Es
gibt KEINE Garantie; auch nicht für MARKTGÄNGIGKEIT oder FÜR SPEZIELLE ZWECKE.
(riscv-ilp32 chroot) farino /tmp # ld --version
GNU ld (Gentoo 2.34 p6) 2.34.0
Copyright (C) 2020 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or (at your option) a later version.
This program has absolutely no warranty.
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