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Message-ID: <CAJgzZoou1wBNK8qHAheR7_haHf1njaTgRZwXnPGX+19qUAbwLg@mail.gmail.com>
Date: Thu, 12 Jun 2025 10:31:03 -0400
From: enh <enh@...gle.com>
To: musl@...ts.openwall.com
Cc: Namhyung Kim <namhyung@...nel.org>, Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: sys/prctl.h differences vs man page
yeah, apologies that i don't think i reported this to the list before,
but android also hit various prctl portability issues trying to use
musl as the host libc and added this ahead of the musl <sys/prctl.h>
as our workaround:
#ifndef _SYS_PRCTL_H
#define _SYS_PRCTL_H
#ifdef __cplusplus
extern "C" {
#endif
#include <stdint.h>
/*
* Get the constants and structs from uapi so that code that
* includes <linux/prctl.h> doesn't conflict with <sys/prctl.h>.
*/
#include <linux/prctl.h>
int prctl (int, ...);
#ifdef __cplusplus
}
#endif
#endif
"we don't duplicate anything that's in a uapi header" is just what
bionic does for everything, all the time, but interestingly
<sys/prctl.h> is a rare header where glibc also doesn't do their usual
copy & paste and just includes <linux/prctl.h> instead. (which is why
this is an issue unique to musl, not one shared with glibc.)
On Thu, Jun 12, 2025 at 2:49 AM Sebastian Andrzej Siewior
<bigeasy@...utronix.de> wrote:
>
> Hi,
>
> the man page for prctl(2) states:
> | SYNOPSIS
> | #include <linux/prctl.h> /* Definition of PR_* constants */
> | #include <sys/prctl.h>
>
> if one is going to include both headers then this happens:
> | In file included from file.c:6:
> | /usr/include/sys/prctl.h:88:8: error: redefinition of 'struct prctl_mm_map'
> | 88 | struct prctl_mm_map {
> | | ^~~~~~~~~~~~
> | In file included from file.c:5:
> | /linux/tools/include/uapi/linux/prctl.h:134:8: note: originally defined here
> | 134 | struct prctl_mm_map {
> | | ^~~~~~~~~~~~
>
> The problem is that musl's provided sys/prctl.h defines the struct
> prctl_mm_map which is a copy of linux kernel's linux/prctl.h. This breaks
> compiles based on the man page because that struct is defined twice.
> It makes it harder to write software which replaces linux/prctl.h with
> current header file while testing for recent features. It also increases
> the maintenance on musl's side to keep that file up to date.
>
> Could you please ship sys/prctl.h which provides the prctl() definition
> and include the PR_* definition from linux/prctl.h?
>
> This problem has been observed on Alpine Linux by Namhyung Kim [0].
>
> [0] https://lore.kernel.org/all/aEh6xO14wDSCFUDr@google.com/T/#u
>
> Sebastian
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