tags 542601 fixed-upstream
thanks
On Thu, Aug 20, 2009 at 1:02 PM, Török Edwin edwinto...@gmail.com wrote:
Package: manpages-dev
Version: 3.22-1
Severity: normal
When _XOPEN_SOURCE is defined the glibc headers no longer define MAP_ANON or
MAP_ANONYMOUS (because _BSD_SOURCE is no longer defined by default).
So if I want to use both pread(2) and mmap(2) in same C source file,
I have to define both _XOPEN_SOURCE and _BSD_SOURCE to get the prototype
for pread *and* MAP_ANON for mmap(2).
The manpage of pread(2) does say that _XOPEN_SOURCE 500 is needed, but doesn't
say that this breaks mmap. mmap's manpage doesn't say that some constants
may not be available under _XOPEN_SOURCE.
Why is _XOPEN_SOURCE 500 even needed for pread? It is a POSIX function,
and defining _XOPEN_SOURCE is not needed for other POSIX functions.
Also the POSIX manpage for pread(3p) doesn't say that _XOPEN_SOURCE is needed,
so this seems like an unnecessary complication on Linux.
If pread(2) was available w/o _XOPEN_SOURCE being defined, then the problem
with using pread and mmap would no longer exist. I think this is rather a
question for glibc though.
I applied the patch below upstream.
Thanks,
Michael
--- a/man2/mmap.2
+++ b/man2/mmap.2
@@ -49,6 +49,8 @@ mmap, munmap \- map or unmap files or devices into memory
.BIint fd , off_t offset );
.BI int munmap(void * addr , size_t length );
.fi
+
+See NOTES for information on feature test macro requirements.
.SH DESCRIPTION
.BR mmap ()
creates a new mapping in the virtual address space of
@@ -541,6 +543,36 @@ If the
flag is specified, and
.I addr
is 0 (NULL), then the mapped address will be 0 (NULL).
+
+Certain
+.I flags
+constants are defined only if either
+.BR _BSD_SOURCE
+or
+.BR _SVID_SOURCE
+is defined.
+(Requiring
+.BR _GNU_SOURCE
+also suffices,
+and requiring that macro specifically would have been more logical,
+since these flags are all Linux specific.)
+The relevant flags are:
+.BR MAP_32BIT ,
+.BR MAP_ANONYMOUS
+(and the synonym
+.BR MAP_ANON ),
+.BR MAP_DENYWRITE ,
+.BR MAP_EXECUTABLE ,
+.BR MAP_FILE ,
+.BR MAP_GROWSDOWN ,
+.BR MAP_HUGETLB ,
+.BR MAP_LOCKED ,
+.BR MAP_NONBLOCK ,
+.BR MAP_NORESERVE ,
+.BR MAP_POPULATE ,
+and
+.BR MAP_STACK .
+
.SH BUGS
On Linux there are no guarantees like those suggested above under
.BR MAP_NORESERVE .
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of The Linux Programming Interface; http://man7.org/tlpi/
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