Subject: [PATCH 2/2] uapi: add a compatibility layer between linux/uio.h and glibc

From: "Dmitry V. Levin" <[email-masked]>
Date: Wed, 22 Feb 2017 05:29:47 +0300

Do not define struct iovec in linux/uio.h when <sys/uio.h> or <fcntl.h>
is already included and provides these definitions.

This fixes the following compilation error when <sys/uio.h> or <fcntl.h>
is included before <linux/uio.h>:

/usr/include/linux/uio.h:16:8: error: redefinition of 'struct iovec'

Signed-off-by: Dmitry V. Levin <[email-masked]>
---
 include/uapi/linux/libc-compat.h | 10 ++++++++++
 include/uapi/linux/uio.h         |  3 +++
 2 files changed, 13 insertions(+)

diff --git a/include/uapi/linux/libc-compat.h b/include/uapi/linux/libc-compat.h
index 481e3b1..9b88586 100644
--- a/include/uapi/linux/libc-compat.h
+++ b/include/uapi/linux/libc-compat.h
@@ -205,6 +205,13 @@
 #define __UAPI_DEF_TIMEZONE		1
 #endif
 
+/* Coordinate with glibc bits/uio.h header. */
+#if defined(_SYS_UIO_H) || defined(_FCNTL_H)
+#define __UAPI_DEF_IOVEC		0
+#else
+#define __UAPI_DEF_IOVEC		1
+#endif
+
 /* Definitions for xattr.h */
 #if defined(_SYS_XATTR_H)
 #define __UAPI_DEF_XATTR		0
@@ -261,6 +268,9 @@
 #define __UAPI_DEF_TIMEVAL			1
 #define __UAPI_DEF_TIMEZONE			1
 
+/* Definitions for uio.h */
+#define __UAPI_DEF_IOVEC		1
+
 /* Definitions for xattr.h */
 #define __UAPI_DEF_XATTR		1
 
diff --git a/include/uapi/linux/uio.h b/include/uapi/linux/uio.h
index 2731d56..e6e12cf 100644
--- a/include/uapi/linux/uio.h
+++ b/include/uapi/linux/uio.h
@@ -9,15 +9,18 @@
 #ifndef _UAPI__LINUX_UIO_H
 #define _UAPI__LINUX_UIO_H
 
+#include <linux/libc-compat.h>
 #include <linux/compiler.h>
 #include <linux/types.h>

+#if __UAPI_DEF_IOVEC
 struct iovec
 {
 	void __user *iov_base;	/* BSD uses caddr_t (1003.1g requires void *) */
 	__kernel_size_t iov_len; /* Must be size_t (1003.1g) */
 };
+#endif /* __UAPI_DEF_IOVEC */
 
 /*
  *	UIO_MAXIOV shall be at least 16 1003.1g (5.4.1.1)
-- 
ldv