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31db7b6a78
The compiler does not know that waitid() will only ever return 0 or -1.
If waitid() would return a positive value than waitpid() would return that
same value and *status would not be initialized.
However users calling waitpid() know that the only possible return values
of it are 0 or -1. They therefore might check for errors with
'ret == -1' or 'ret < 0' and use *status otherwise. The compiler will then
warn about the usage of a potentially uninitialized variable.
Example:
$ cat test.c
#include <stdio.h>
#include <unistd.h>
int main(void)
{
int ret, status;
ret = waitpid(0, &status, 0);
if (ret == -1)
return 0;
printf("status %x\n", status);
return 0;
}
$ gcc --version
gcc (GCC) 15.1.1 20250425
$ gcc -Wall -Os -Werror -nostdlib -nostdinc -static -Iusr/include -Itools/include/nolibc/ -o /dev/null test.c
test.c: In function ‘main’:
test.c:12:9: error: ‘status’ may be used uninitialized [-Werror=maybe-uninitialized]
12 | printf("status %x\n", status);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
test.c:6:18: note: ‘status’ was declared here
6 | int ret, status;
| ^~~~~~
cc1: all warnings being treated as errors
Avoid the warning by normalizing waitid() errors to '-1' in waitpid().
Fixes: 0c89abf5ab ("tools/nolibc: implement waitpid() in terms of waitid()")
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20250707-nolibc-waitpid-uninitialized-v1-1-dcd4e70bcd8f@linutronix.de
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
116 lines
2.4 KiB
C
116 lines
2.4 KiB
C
/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
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/*
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* wait definitions for NOLIBC
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* Copyright (C) 2017-2021 Willy Tarreau <w@1wt.eu>
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*/
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/* make sure to include all global symbols */
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#include "../nolibc.h"
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#ifndef _NOLIBC_SYS_WAIT_H
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#define _NOLIBC_SYS_WAIT_H
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#include "../arch.h"
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#include "../std.h"
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#include "../types.h"
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/*
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* pid_t wait(int *status);
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* pid_t wait4(pid_t pid, int *status, int options, struct rusage *rusage);
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* pid_t waitpid(pid_t pid, int *status, int options);
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* int waitid(idtype_t idtype, id_t id, siginfo_t *infop, int options);
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*/
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static __attribute__((unused))
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pid_t sys_wait4(pid_t pid, int *status, int options, struct rusage *rusage)
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{
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#ifdef __NR_wait4
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return my_syscall4(__NR_wait4, pid, status, options, rusage);
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#else
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return __nolibc_enosys(__func__, pid, status, options, rusage);
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#endif
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}
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static __attribute__((unused))
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pid_t wait4(pid_t pid, int *status, int options, struct rusage *rusage)
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{
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return __sysret(sys_wait4(pid, status, options, rusage));
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}
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static __attribute__((unused))
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int sys_waitid(int which, pid_t pid, siginfo_t *infop, int options, struct rusage *rusage)
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{
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return my_syscall5(__NR_waitid, which, pid, infop, options, rusage);
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}
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static __attribute__((unused))
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int waitid(int which, pid_t pid, siginfo_t *infop, int options)
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{
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return __sysret(sys_waitid(which, pid, infop, options, NULL));
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}
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static __attribute__((unused))
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pid_t waitpid(pid_t pid, int *status, int options)
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{
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int idtype, ret;
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siginfo_t info;
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pid_t id;
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if (pid == INT_MIN) {
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SET_ERRNO(ESRCH);
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return -1;
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} else if (pid < -1) {
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idtype = P_PGID;
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id = -pid;
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} else if (pid == -1) {
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idtype = P_ALL;
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id = 0;
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} else if (pid == 0) {
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idtype = P_PGID;
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id = 0;
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} else {
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idtype = P_PID;
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id = pid;
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}
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options |= WEXITED;
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ret = waitid(idtype, id, &info, options);
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if (ret)
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return -1;
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switch (info.si_code) {
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case 0:
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*status = 0;
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break;
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case CLD_EXITED:
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*status = (info.si_status & 0xff) << 8;
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break;
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case CLD_KILLED:
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*status = info.si_status & 0x7f;
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break;
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case CLD_DUMPED:
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*status = (info.si_status & 0x7f) | 0x80;
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break;
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case CLD_STOPPED:
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case CLD_TRAPPED:
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*status = (info.si_status << 8) + 0x7f;
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break;
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case CLD_CONTINUED:
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*status = 0xffff;
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break;
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default:
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return -1;
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}
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return info.si_pid;
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}
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static __attribute__((unused))
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pid_t wait(int *status)
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{
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return waitpid(-1, status, 0);
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}
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#endif /* _NOLIBC_SYS_WAIT_H */
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