On Thu, Mar 28, 2024 at 2:11 AM Alejandro Colomar <alx@xxxxxxxxxx> wrote:
>
> Hi Elliott,
>
> On Wed, Mar 27, 2024 at 05:20:18PM -0700, enh wrote:
> > > Do you intend to send patches? Otherwise, let me know, and I'll prepare
> > > something.
> >
> > i can do, but it also sounds like enough of a bikeshed that i imagine
> > you'd only want to rewrite it again anyway :-)
>
> Actually, I tried to write something, and felt like you'll definitely do
> better; I didn't like my text. Please send a patch. (I can do the
> bikeshed when applying it, if you don't feel like entertaining it.) :-}
heh, i didn't even write mine out and had the same worry. oh well,
i've attached something so at least we have something concrete to talk
about!
> > (i was actually surprised how many references to glibc 2.0 there are
> > in various man pages, and even more amused by references to "ancient
> > versions of glibc" being defined as "before glibc 2.0", as if 1997
> > isn't ancient :-) )
>
> You can move anything like that to HISTORY sections in any page you see
> it. In some cases, it might make sense to remove it, but only if it was
> a small bug.
>
> Have a lovely day!
> Alex
>
> --
> <https://www.alejandro-colomar.es/>
> Looking for a remote C programming job at the moment.
From e4e24a6a7ef66016edcd735f3cebc7f6583e716a Mon Sep 17 00:00:00 2001
From: Elliott Hughes <enh@xxxxxxxxxx>
Date: Fri, 29 Mar 2024 17:10:26 -0700
Subject: [PATCH] getpagesize.2/syscalls.2: modernization.
Remove the HP-UX portability advice, since getpagesize() is a slightly
better option than sysconf() for Linux systems.
Explain why this function exists, and why this man page is in the wrong
section. (The previous text tried to do both at the same, which was
confusing.) Also explain how the vast majority of architectures that
don't have a syscall (but do support multiple page sizes) actually work.
Also de-emphasize the glibc 2.0 bug, since most people don't need to
worry about compatibility with versions of glibc from 1997.
Finally, change "not on x86" in syscalls.2 to say where there _is_ a
syscall.
---
man2/getpagesize.2 | 47 ++++++++++------------------------------------
man2/syscalls.2 | 4 +++-
2 files changed, 13 insertions(+), 38 deletions(-)
diff --git a/man2/getpagesize.2 b/man2/getpagesize.2
index b82586f36..5d0006f04 100644
--- a/man2/getpagesize.2
+++ b/man2/getpagesize.2
@@ -44,46 +44,19 @@ This call first appeared in 4.2BSD.
SVr4, 4.4BSD, SUSv2.
In SUSv2 the
.BR getpagesize ()
-call is labeled LEGACY, and in POSIX.1-2001
-it has been dropped;
-HP-UX does not have this call.
+call was labeled LEGACY, and it was removed in POSIX.1-2001.
.SH NOTES
-Portable applications should employ
-.I sysconf(_SC_PAGESIZE)
-instead of
-.BR getpagesize ():
-.P
-.in +4n
-.EX
-#include <unistd.h>
-long sz = sysconf(_SC_PAGESIZE);
-.EE
-.in
-.P
-(Most systems allow the synonym
-.B _SC_PAGE_SIZE
-for
-.BR _SC_PAGESIZE .)
-.P
-Whether
-.BR getpagesize ()
-is present as a Linux system call depends on the architecture.
-If it is, it returns the kernel symbol
-.BR PAGE_SIZE ,
-whose value depends on the architecture and machine model.
-Generally, one uses binaries that are dependent on the architecture but not
-on the machine model, in order to have a single binary
-distribution per architecture.
-This means that a user program
-should not find
+A user program should not hard-code a page size,
+neither as a literal nor using the
.B PAGE_SIZE
-at compile time from a header file,
-but use an actual system call, at least for those architectures
-(like sun4) where this dependency exists.
-Here glibc 2.0 fails because its
+macro, because some architectures support multiple page sizes.
+.P
+This manual page is in section 2 because Alpha, SPARC, and SPARC64
+all have a Linux system call
.BR getpagesize ()
-returns a statically derived value, and does not use a system call.
-Things are OK in glibc 2.1.
+though other architectures do not, and use the ELF auxiliary vector
+instead. glibc 2.0 returned a constant even on architectures with mutliple
+page sizes.
.SH SEE ALSO
.BR mmap (2),
.BR sysconf (3)
diff --git a/man2/syscalls.2 b/man2/syscalls.2
index 6c2313506..69f24ef29 100644
--- a/man2/syscalls.2
+++ b/man2/syscalls.2
@@ -324,7 +324,9 @@ T}
\fBgetpeername\fP(2) 2.0 T{
See notes on \fBsocketcall\fP(2)
T}
-\fBgetpagesize\fP(2) 2.0 Not on x86
+\fBgetpagesize\fP(2) 2.0 T{
+Alpha, SPARC/SPARC64 only
+T}
\fBgetpgid\fP(2) 1.0
\fBgetpgrp\fP(2) 1.0
\fBgetpid\fP(2) 1.0
--
2.44.0.478.gd926399ef9-goog
