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authorZack Weinberg <zackw@panix.com>2017-03-22 10:55:38 -0400
committerZack Weinberg <zackw@panix.com>2017-06-14 07:51:30 -0400
commit37f802f86400684c8d13403958b2c598721d6360 (patch)
tree1e7281fbdff02e8e0818300cf0ac1d496956d1a9
parent0572433b5beb636de1a49ec6b4fdab830c38cdc5 (diff)
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Remove __need_IOV_MAX and __need_FOPEN_MAX.
__need_FOPEN_MAX wasn't being used anywhere. __need_IOV_MAX was more complicated; the basic deal is that sys/uio.h wants to define a constant named UIO_MAXIOV and bits/xopen_lim.h wants to define a constant named IOV_MAX, with the same meaning. For no apparent reason this was being handled via bits/stdio_lim.h -- stdio.h is NOT supposed to define IOV_MAX -- and some mess in Makerules. Also, bits/uio.h on Linux was being used as a dumping ground for extension functions. So now we have bits/uio_lim.h, which defines __IOV_MAX. bits/xopen_lim.h and sys/uio.h use that to define their respective constants. We also now have bits/uio-ext.h, which is the official Proper Home for extensions to sys/uio.h. bits/uio.h is removed, and stdio_lim.h doesn't define IOV_MAX at all. * bits/uio_lim.h, sysdeps/unix/sysv/linux/bits/uio_lim.h * bits/uio-ext.h, sysdeps/unix/sysv/linux/bits/uio-ext.h: New file. * bits/uio.h, sysdeps/unix/sysv/linux/bits/uio.h: Delete file. * include/bits/xopen_lim.h: Use bits/uio_lim.h to get the value for IOV_MAX. * misc/Makefile: Install bits/uio-ext.h and bits/uio_lim.h. Don't install bits/uio.h. * misc/sys/uio.h: Don't include bits/uio.h. Do include bits/types/struct_iovec.h and bits/uio_lim.h. Set UIO_MAXIOV based on __IOV_MAX. Under __USE_GNU, also include bits/uio-ext.h. * stdio-common/stdio_lim.h.in: Remove logic for __need_FOPEN_MAX and __need_IOV_MAX. Don't define IOV_MAX at all. * Makerules (stdio_lim.h): Remove logic for setting IOV_MAX. * sysdeps/unix/sysv/linux/bits/fcntl-linux.h: Include bits/types/struct_iovec.h, not bits/uio.h. Use __ssize_t, not ssize_t, in function prototypes. Don't use hard TAB for double space after period in comments.
-rw-r--r--ChangeLog23
-rw-r--r--Makerules10
-rw-r--r--bits/uio-ext.h28
-rw-r--r--bits/uio_lim.h (renamed from bits/uio.h)13
-rw-r--r--include/bits/xopen_lim.h13
-rw-r--r--misc/Makefile3
-rw-r--r--misc/sys/uio.h18
-rw-r--r--stdio-common/stdio_lim.h.in31
-rw-r--r--sysdeps/unix/sysv/linux/bits/fcntl-linux.h52
-rw-r--r--sysdeps/unix/sysv/linux/bits/uio-ext.h (renamed from sysdeps/unix/sysv/linux/bits/uio.h)44
-rw-r--r--sysdeps/unix/sysv/linux/bits/uio_lim.h32
11 files changed, 164 insertions, 103 deletions
diff --git a/ChangeLog b/ChangeLog
index a06a70c..f7c9635 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,26 @@
+2017-06-14 Zack Weinberg <zackw@panix.com>
+
+ * bits/uio_lim.h, sysdeps/unix/sysv/linux/bits/uio_lim.h
+ * bits/uio-ext.h, sysdeps/unix/sysv/linux/bits/uio-ext.h: New file.
+ * bits/uio.h, sysdeps/unix/sysv/linux/bits/uio.h: Delete file.
+
+ * include/bits/xopen_lim.h: Use bits/uio_lim.h to get the value
+ for IOV_MAX.
+ * misc/Makefile: Install bits/uio-ext.h and bits/uio_lim.h.
+ Don't install bits/uio.h.
+ * misc/sys/uio.h: Don't include bits/uio.h. Do include
+ bits/types/struct_iovec.h and bits/uio_lim.h. Set UIO_MAXIOV
+ based on __IOV_MAX. Under __USE_GNU, also include bits/uio-ext.h.
+
+ * stdio-common/stdio_lim.h.in: Remove logic for __need_FOPEN_MAX
+ and __need_IOV_MAX. Don't define IOV_MAX at all.
+ * Makerules (stdio_lim.h): Remove logic for setting IOV_MAX.
+
+ * sysdeps/unix/sysv/linux/bits/fcntl-linux.h:
+ Include bits/types/struct_iovec.h, not bits/uio.h.
+ Use __ssize_t, not ssize_t, in function prototypes.
+ Don't use hard TAB for double space after period in comments.
+
2017-06-14 Alan Modra <amodra@gmail.com>
* elf/elf.h (PPC64_OPT_LOCALENTRY): Define.
diff --git a/Makerules b/Makerules
index f91a4c5..9bb707c 100644
--- a/Makerules
+++ b/Makerules
@@ -1521,8 +1521,7 @@ $(stdio_lim:h=st): $(..)stdio-common/stdio_lim.h.in $(..)Rules \
$(common-objpfx)config.make
$(make-target-directory)
{ echo '#include "$(..)posix/bits/posix1_lim.h"'; \
- echo '#define _LIBC 1'; \
- echo '#include "$(..)misc/sys/uio.h"'; } | \
+ } | \
$(CC) -E -dM -MD -MP -MF $(@:st=dT) -MT '$(@:st=h) $(@:st=d)' \
$(CPPUNDEFS) $(+includes) -xc - -o $(@:st=hT)
sed $(sed-remove-objpfx) $(sed-remove-dotdot) \
@@ -1530,21 +1529,14 @@ $(stdio_lim:h=st): $(..)stdio-common/stdio_lim.h.in $(..)Rules \
mv -f $(@:st=dt) $(@:st=d)
fopen_max=`sed -n 's/^#define OPEN_MAX //1p' $(@:st=hT)`; \
filename_max=`sed -n 's/^#define PATH_MAX //1p' $(@:st=hT)`; \
- iov_max=`sed -n 's/^#define UIO_MAXIOV //p' $(@:st=hT)`; \
fopen_max=$${fopen_max:-16}; \
filename_max=$${filename_max:-1024}; \
- if [ -z "$$iov_max" ]; then \
- define_iov_max="# undef IOV_MAX"; \
- else \
- define_iov_max="# define IOV_MAX $$iov_max"; \
- fi; \
sed -e "s/@FOPEN_MAX@/$$fopen_max/" \
-e "s/@FILENAME_MAX@/$$filename_max/" \
-e "s/@L_tmpnam@/$(L_tmpnam)/" \
-e "s/@TMP_MAX@/$(TMP_MAX)/" \
-e "s/@L_ctermid@/$(L_ctermid)/" \
-e "s/@L_cuserid@/$(L_cuserid)/" \
- -e "s/@define_IOV_MAX@/$$define_iov_max/" \
$< > $(@:st=h.new)
$(move-if-change) $(@:st=h.new) $(@:st=h)
# Remove these last so that they can be examined if something went wrong.
diff --git a/bits/uio-ext.h b/bits/uio-ext.h
new file mode 100644
index 0000000..cd4039c
--- /dev/null
+++ b/bits/uio-ext.h
@@ -0,0 +1,28 @@
+/* Operating system-specific extensions to sys/uio.h - generic version.
+ Copyright (C) 2017 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _BITS_UIO_EXT_H
+#define _BITS_UIO_EXT_H 1
+
+#ifndef _SYS_UIO_H
+# error "Never include <bits/uio-ext.h> directly; use <sys/uio.h> instead."
+#endif
+
+/* This operating system does not extend sys/uio.h. */
+
+#endif /* sys/uio_ext.h */
diff --git a/bits/uio.h b/bits/uio_lim.h
index 96a3a71..63afbdc 100644
--- a/bits/uio.h
+++ b/bits/uio_lim.h
@@ -1,4 +1,5 @@
-/* Copyright (C) 1996-2017 Free Software Foundation, Inc.
+/* Implementation limits related to sys/uio.h - generic version.
+ Copyright (C) 2017 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
@@ -15,9 +16,11 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
-#ifndef _SYS_UIO_H
-# error "Never include <bits/uio.h> directly; use <sys/uio.h> instead."
-#endif
+#ifndef _BITS_UIO_LIM_H
+#define _BITS_UIO_LIM_H 1
+/* Maximum length of the 'struct iovec' array in a single call to
+ readv or writev. If there is no limit, the macro is not defined. */
+#undef __IOV_MAX
-#include <bits/types/struct_iovec.h>
+#endif
diff --git a/include/bits/xopen_lim.h b/include/bits/xopen_lim.h
index 2ae7cb3..4c5e62f 100644
--- a/include/bits/xopen_lim.h
+++ b/include/bits/xopen_lim.h
@@ -29,9 +29,6 @@
#ifndef _XOPEN_LIM_H
#define _XOPEN_LIM_H 1
-#define __need_IOV_MAX
-#include <bits/stdio_lim.h>
-
/* We do not provide fixed values for
ARG_MAX Maximum length of argument to the `exec' function
@@ -60,10 +57,16 @@
*/
-/* Maximum number of `iovec' structures that one process has available
- for use with `readv' or writev'. */
+/* Maximum number of `iovec' structures that may be used in a single call
+ to `readv', `writev', etc. */
#define _XOPEN_IOV_MAX _POSIX_UIO_MAXIOV
+#include <bits/uio_lim.h>
+#ifdef __IOV_MAX
+# define IOV_MAX __IOV_MAX
+#else
+# undef IOV_MAX
+#endif
/* Maximum value of `digit' in calls to the `printf' and `scanf'
functions. We have no limit, so return a reasonable value. */
diff --git a/misc/Makefile b/misc/Makefile
index 46072e6..8660b6f 100644
--- a/misc/Makefile
+++ b/misc/Makefile
@@ -23,7 +23,8 @@ subdir := misc
include ../Makeconfig
-headers := sys/uio.h bits/uio.h sys/ioctl.h bits/ioctls.h bits/ioctl-types.h \
+headers := sys/uio.h bits/uio-ext.h bits/uio_lim.h \
+ sys/ioctl.h bits/ioctls.h bits/ioctl-types.h \
sys/ptrace.h sys/file.h sys/dir.h sys/cdefs.h \
ar.h a.out.h libgen.h stab.h bits/stab.def sgtty.h \
ttyent.h paths.h sys/reboot.h \
diff --git a/misc/sys/uio.h b/misc/sys/uio.h
index 66c22f0..2ae918a 100644
--- a/misc/sys/uio.h
+++ b/misc/sys/uio.h
@@ -19,15 +19,17 @@
#define _SYS_UIO_H 1
#include <features.h>
-
#include <sys/types.h>
+#include <bits/types/struct_iovec.h>
+#include <bits/uio_lim.h>
+#ifdef __IOV_MAX
+# define UIO_MAXIOV __IOV_MAX
+#else
+# undef UIO_MAXIOV
+#endif
__BEGIN_DECLS
-/* This file defines `struct iovec'. */
-#include <bits/uio.h>
-
-
/* Read data from file descriptor FD, and put the result in the
buffers described by IOVEC, which is a vector of COUNT 'struct iovec's.
The buffers are filled in the order specified.
@@ -160,4 +162,10 @@ extern ssize_t pwritev64v2 (int __fd, const struct iovec *__iodev,
__END_DECLS
+/* Some operating systems provide system-specific extensions to this
+ header. */
+#ifdef __USE_GNU
+# include <bits/uio-ext.h>
+#endif
+
#endif /* sys/uio.h */
diff --git a/stdio-common/stdio_lim.h.in b/stdio-common/stdio_lim.h.in
index 510bf00..5288907 100644
--- a/stdio-common/stdio_lim.h.in
+++ b/stdio-common/stdio_lim.h.in
@@ -15,28 +15,25 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
-#if !defined _STDIO_H && !defined __need_FOPEN_MAX && !defined __need_IOV_MAX
+#ifndef _BITS_STDIO_LIM_H
+#define _BITS_STDIO_LIM_H 1
+
+#ifndef _STDIO_H
# error "Never include <bits/stdio_lim.h> directly; use <stdio.h> instead."
#endif
-#ifdef _STDIO_H
-# define L_tmpnam @L_tmpnam@
-# define TMP_MAX @TMP_MAX@
-# define FILENAME_MAX @FILENAME_MAX@
+#define L_tmpnam @L_tmpnam@
+#define TMP_MAX @TMP_MAX@
+#define FILENAME_MAX @FILENAME_MAX@
-# ifdef __USE_POSIX
-# define L_ctermid @L_ctermid@
-# if !defined __USE_XOPEN2K || defined __USE_GNU
-# define L_cuserid @L_cuserid@
-# endif
+#ifdef __USE_POSIX
+# define L_ctermid @L_ctermid@
+# if !defined __USE_XOPEN2K || defined __USE_GNU
+# define L_cuserid @L_cuserid@
# endif
#endif
-#if defined __need_FOPEN_MAX || defined _STDIO_H
-# undef FOPEN_MAX
-# define FOPEN_MAX @FOPEN_MAX@
-#endif
+#undef FOPEN_MAX
+#define FOPEN_MAX @FOPEN_MAX@
-#if defined __need_IOV_MAX && !defined IOV_MAX
-@define_IOV_MAX@
-#endif
+#endif /* bits/stdio_lim.h */
diff --git a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
index 59d6631..0cd0a5d 100644
--- a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
+++ b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
@@ -35,7 +35,7 @@
*/
#ifdef __USE_GNU
-# include <bits/uio.h>
+# include <bits/types/struct_iovec.h>
#endif
/* open/fcntl. */
@@ -76,7 +76,7 @@
#endif
#ifndef __O_DIRECTORY
-# define __O_DIRECTORY 0200000
+# define __O_DIRECTORY 0200000
#endif
#ifndef __O_NOFOLLOW
# define __O_NOFOLLOW 0400000
@@ -104,9 +104,9 @@
# ifndef __USE_FILE_OFFSET64
# define F_GETLK 5 /* Get record locking info. */
# define F_SETLK 6 /* Set record locking info (non-blocking). */
-# define F_SETLKW 7 /* Set record locking info (blocking). */
+# define F_SETLKW 7 /* Set record locking info (blocking). */
# else
-# define F_GETLK F_GETLK64 /* Get record locking info. */
+# define F_GETLK F_GETLK64 /* Get record locking info. */
# define F_SETLK F_SETLK64 /* Set record locking info (non-blocking).*/
# define F_SETLKW F_SETLKW64 /* Set record locking info (blocking). */
# endif
@@ -114,7 +114,7 @@
#ifndef F_GETLK64
# define F_GETLK64 12 /* Get record locking info. */
# define F_SETLK64 13 /* Set record locking info (non-blocking). */
-# define F_SETLKW64 14 /* Set record locking info (blocking). */
+# define F_SETLKW64 14 /* Set record locking info (blocking). */
#endif
/* open file description locks.
@@ -139,27 +139,27 @@
#endif
#ifdef __USE_XOPEN2K8
-# define O_DIRECTORY __O_DIRECTORY /* Must be a directory. */
-# define O_NOFOLLOW __O_NOFOLLOW /* Do not follow links. */
+# define O_DIRECTORY __O_DIRECTORY /* Must be a directory. */
+# define O_NOFOLLOW __O_NOFOLLOW /* Do not follow links. */
# define O_CLOEXEC __O_CLOEXEC /* Set close_on_exec. */
#endif
#ifdef __USE_GNU
-# define O_DIRECT __O_DIRECT /* Direct disk access. */
+# define O_DIRECT __O_DIRECT /* Direct disk access. */
# define O_NOATIME __O_NOATIME /* Do not set atime. */
# define O_PATH __O_PATH /* Resolve pathname but do not open file. */
# define O_TMPFILE __O_TMPFILE /* Atomically create nameless file. */
#endif
-/* For now, Linux has no separate synchronicitiy options for read
+/* For now, Linux has no separate synchronicity options for read
operations. We define O_RSYNC therefore as the same as O_SYNC
since this is a superset. */
#if defined __USE_POSIX199309 || defined __USE_UNIX98
# define O_DSYNC __O_DSYNC /* Synchronize data. */
# if defined __O_RSYNC
-# define O_RSYNC __O_RSYNC /* Synchronize read operations. */
+# define O_RSYNC __O_RSYNC /* Synchronize read operations. */
# else
-# define O_RSYNC O_SYNC /* Synchronize read operations. */
+# define O_RSYNC O_SYNC /* Synchronize read operations. */
# endif
#endif
@@ -197,7 +197,7 @@
#endif
#ifdef __USE_GNU
-# define F_SETLEASE 1024 /* Set a lease. */
+# define F_SETLEASE 1024 /* Set a lease. */
# define F_GETLEASE 1025 /* Enquire what lease is active. */
# define F_NOTIFY 1026 /* Request notifications on a directory. */
# define F_SETPIPE_SZ 1031 /* Set pipe page size array. */
@@ -214,8 +214,8 @@
#ifndef F_RDLCK
/* For posix fcntl() and `l_type' field of a `struct flock' for lockf(). */
# define F_RDLCK 0 /* Read lock. */
-# define F_WRLCK 1 /* Write lock. */
-# define F_UNLCK 2 /* Remove lock. */
+# define F_WRLCK 1 /* Write lock. */
+# define F_UNLCK 2 /* Remove lock. */
#endif
@@ -235,10 +235,10 @@
#endif
#ifdef __USE_GNU
-# define LOCK_MAND 32 /* This is a mandatory flock: */
-# define LOCK_READ 64 /* ... which allows concurrent read operations. */
+# define LOCK_MAND 32 /* This is a mandatory flock: */
+# define LOCK_READ 64 /* ... which allows concurrent read operations. */
# define LOCK_WRITE 128 /* ... which allows concurrent write operations. */
-# define LOCK_RW 192 /* ... Which allows concurrent read & write operations. */
+# define LOCK_RW 192 /* ... Which allows concurrent read & write operations. */
#endif
#ifdef __USE_GNU
@@ -289,7 +289,7 @@ struct f_owner_ex
#ifdef __USE_XOPEN2K
# define POSIX_FADV_NORMAL 0 /* No further special treatment. */
# define POSIX_FADV_RANDOM 1 /* Expect random page references. */
-# define POSIX_FADV_SEQUENTIAL 2 /* Expect sequential page references. */
+# define POSIX_FADV_SEQUENTIAL 2 /* Expect sequential page references. */
# define POSIX_FADV_WILLNEED 3 /* Will need these pages. */
# define POSIX_FADV_DONTNEED __POSIX_FADV_DONTNEED /* Don't need these pages. */
# define POSIX_FADV_NOREUSE __POSIX_FADV_NOREUSE /* Data will be accessed once. */
@@ -339,7 +339,7 @@ __BEGIN_DECLS
#ifdef __USE_GNU
/* Provide kernel hint to read ahead. */
-extern ssize_t readahead (int __fd, __off64_t __offset, size_t __count)
+extern __ssize_t readahead (int __fd, __off64_t __offset, size_t __count)
__THROW;
@@ -355,23 +355,23 @@ extern int sync_file_range (int __fd, __off64_t __offset, __off64_t __count,
This function is a possible cancellation point and therefore not
marked with __THROW. */
-extern ssize_t vmsplice (int __fdout, const struct iovec *__iov,
- size_t __count, unsigned int __flags);
+extern __ssize_t vmsplice (int __fdout, const struct iovec *__iov,
+ size_t __count, unsigned int __flags);
/* Splice two files together.
This function is a possible cancellation point and therefore not
marked with __THROW. */
-extern ssize_t splice (int __fdin, __off64_t *__offin, int __fdout,
- __off64_t *__offout, size_t __len,
- unsigned int __flags);
+extern __ssize_t splice (int __fdin, __off64_t *__offin, int __fdout,
+ __off64_t *__offout, size_t __len,
+ unsigned int __flags);
/* In-kernel implementation of tee for pipe buffers.
This function is a possible cancellation point and therefore not
marked with __THROW. */
-extern ssize_t tee (int __fdin, int __fdout, size_t __len,
- unsigned int __flags);
+extern __ssize_t tee (int __fdin, int __fdout, size_t __len,
+ unsigned int __flags);
/* Reserve storage for the data of the file associated with FD.
diff --git a/sysdeps/unix/sysv/linux/bits/uio.h b/sysdeps/unix/sysv/linux/bits/uio-ext.h
index d5701f8..4ddb644 100644
--- a/sysdeps/unix/sysv/linux/bits/uio.h
+++ b/sysdeps/unix/sysv/linux/bits/uio-ext.h
@@ -1,4 +1,5 @@
-/* Copyright (C) 1996-2017 Free Software Foundation, Inc.
+/* Operating system-specific extensions to sys/uio.h - Linux version.
+ Copyright (C) 1996-2017 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
@@ -15,39 +16,13 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
-#if !defined _SYS_UIO_H && !defined _FCNTL_H
-# error "Never include <bits/uio.h> directly; use <sys/uio.h> instead."
-#endif
-
-#ifndef _BITS_UIO_H
-#define _BITS_UIO_H 1
-
-#include <sys/types.h>
-
-
-/* We should normally use the Linux kernel header file to define this
- type and macros but this calls for trouble because of the header
- includes other kernel headers. */
-
-/* Size of object which can be written atomically.
-
- This macro has different values in different kernel versions. The
- latest versions of the kernel use 1024 and this is good choice. Since
- the C library implementation of readv/writev is able to emulate the
- functionality even if the currently running kernel does not support
- this large value the readv/writev call will not fail because of this. */
-#define UIO_MAXIOV 1024
-
-
-#include <bits/types/struct_iovec.h>
+#ifndef _BITS_UIO_EXT_H
+#define _BITS_UIO_EXT_H 1
+#ifndef _SYS_UIO_H
+# error "Never include <bits/uio-ext.h> directly; use <sys/uio.h> instead."
#endif
-
-#ifdef __USE_GNU
-# if defined _SYS_UIO_H && !defined _BITS_UIO_H_FOR_SYS_UIO_H
-# define _BITS_UIO_H_FOR_SYS_UIO_H 1
-
__BEGIN_DECLS
/* Read from another process' address space. */
@@ -66,13 +41,12 @@ extern ssize_t process_vm_writev (pid_t __pid, const struct iovec *__lvec,
unsigned long int __flags)
__THROW;
-__END_DECLS
-
-# endif
/* Flags for preadv2/pwritev2: */
#define RWF_HIPRI 0x00000001 /* High priority request. */
#define RWF_DSYNC 0x00000002 /* per-IO O_DSYNC. */
#define RWF_SYNC 0x00000004 /* per-IO O_SYNC. */
-#endif
+__END_DECLS
+
+#endif /* bits/uio-ext.h */
diff --git a/sysdeps/unix/sysv/linux/bits/uio_lim.h b/sysdeps/unix/sysv/linux/bits/uio_lim.h
new file mode 100644
index 0000000..26c0b67
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/bits/uio_lim.h
@@ -0,0 +1,32 @@
+/* Implementation limits related to sys/uio.h - Linux version.
+ Copyright (C) 2017 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _BITS_UIO_LIM_H
+#define _BITS_UIO_LIM_H 1
+
+/* Maximum length of the 'struct iovec' array in a single call to
+ readv or writev.
+
+ This macro has different values in different kernel versions. The
+ latest versions of the kernel use 1024 and this is good choice. Since
+ the C library implementation of readv/writev is able to emulate the
+ functionality even if the currently running kernel does not support
+ this large value the readv/writev call will not fail because of this. */
+#define __IOV_MAX 1024
+
+#endif