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Subject[PATCH tip/timers/core] uapi glibc compat: make linux/time.h compile after libc time.h files
Date
From: Willem de Bruijn <willemb@google.com>

Add libc-compat workaround for definitions in linux/time.h that
duplicate those in libc time.h, sys/time.h and bits/time.h.

With this change, userspace builds succeeds when linux/time.h is
included after those libc files. The inverse requires changes to
those userspace headers.

Without this patch, when compiling the following program after
make headers_install:

echo -e "#include <time.h>\n#include <linux/time.h>" | \
gcc -Wall -Werror -Iusr/include -c -xc -

gcc gives these errors:

#include <time.h>
#include <linux/time.h>

In file included from ../test_time.c:3:0:
/usr/include/time.h:120:8: error: redefinition of ‘struct timespec’
struct timespec
^
In file included from ../test_time.c:2:0:
./usr/include/linux/time.h:9:8: note: originally defined here
struct timespec {
^
In file included from ../test_time.c:3:0:
/usr/include/time.h:161:8: error: redefinition of ‘struct itimerspec’
struct itimerspec
^
In file included from ../test_time.c:2:0:
./usr/include/linux/time.h:34:8: note: originally defined here
struct itimerspec {

and this warning by indirect inclusion of bits/time.h:

In file included from ../test_time.c:4:0:
./usr/include/linux/time.h:67:0: error: "TIMER_ABSTIME" redefined [-Werror]
#define TIMER_ABSTIME 0x01
^
In file included from /usr/include/time.h:41:0,
from ../test_time.c:3:
/usr/include/x86_64-linux-gnu/bits/time.h:82:0: note: this is the location of the previous definition
# define TIMER_ABSTIME 1
^

Ran the same program for sys/time.h and bits/time.h. The _SYS_TIME_H
test resolves similar errors for timeval, timezone, itimerval and
warnings for ITIMER_REAL, ITIMER_VIRTUAL, ITIMER_PROF.

Signed-off-by: Willem de Bruijn <willemb@google.com>
---
include/uapi/linux/libc-compat.h | 50 ++++++++++++++++++++++++++++++++++++++++
include/uapi/linux/time.h | 15 ++++++++++++
2 files changed, 65 insertions(+)

diff --git a/include/uapi/linux/libc-compat.h b/include/uapi/linux/libc-compat.h
index e4f048e..9c3cbf5 100644
--- a/include/uapi/linux/libc-compat.h
+++ b/include/uapi/linux/libc-compat.h
@@ -146,6 +146,43 @@
#define __UAPI_DEF_XATTR 1
#endif

+/* Definitions for time.h */
+#if defined(__timespec_defined)
+#define __UAPI_DEF_TIMESPEC 0
+#else
+#define __UAPI_DEF_TIMESPEC 1
+#endif
+
+#if defined(_TIME_H) && defined(__USE_POSIX199309)
+#define __UAPI_DEF_ITIMERSPEC 0
+#else
+#define __UAPI_DEF_ITIMERSPEC 1
+#endif
+
+/* Definitions for sys/time.h */
+#if defined(_SYS_TIME_H)
+#define __UAPI_DEF_TIMEVAL 0
+#define __UAPI_DEF_ITIMERVAL 0
+#define __UAPI_DEF_ITIMER_WHICH 0
+#else
+#define __UAPI_DEF_TIMEVAL 1
+#define __UAPI_DEF_ITIMERVAL 1
+#define __UAPI_DEF_ITIMER_WHICH 1
+#endif
+
+/* Definitions for bits/time.h */
+#if defined(_BITS_TIME_H)
+#define __UAPI_DEF_ABSTIME 0
+#else
+#define __UAPI_DEF_ABSTIME 1
+#endif
+
+#if defined(_SYS_TIME_H) && defined(__USE_BSD)
+#define __UAPI_DEF_TIMEZONE 0
+#else
+#define __UAPI_DEF_TIMEZONE 1
+#endif
+
/* If we did not see any headers from any supported C libraries,
* or we are being included in the kernel, then define everything
* that we need. */
@@ -182,6 +219,19 @@
/* Definitions for xattr.h */
#define __UAPI_DEF_XATTR 1

+/* Definitions for time.h */
+#define __UAPI_DEF_TIMESPEC 1
+#define __UAPI_DEF_ITIMERSPEC 1
+
+/* Definitions for sys/time.h */
+#define __UAPI_DEF_TIMEVAL 1
+#define __UAPI_DEF_ITIMERVAL 1
+#define __UAPI_DEF_ITIMER_WHICH 1
+#define __UAPI_DEF_TIMEZONE 1
+
+/* Definitions for bits/time.h */
+#define __UAPI_DEF_ABSTIME 1
+
#endif /* __GLIBC__ */

#endif /* _UAPI_LIBC_COMPAT_H */
diff --git a/include/uapi/linux/time.h b/include/uapi/linux/time.h
index e75e1b6..4e7333c 100644
--- a/include/uapi/linux/time.h
+++ b/include/uapi/linux/time.h
@@ -1,9 +1,11 @@
#ifndef _UAPI_LINUX_TIME_H
#define _UAPI_LINUX_TIME_H

+#include <linux/libc-compat.h>
#include <linux/types.h>


+#if __UAPI_DEF_TIMESPEC
#ifndef _STRUCT_TIMESPEC
#define _STRUCT_TIMESPEC
struct timespec {
@@ -11,35 +13,46 @@ struct timespec {
long tv_nsec; /* nanoseconds */
};
#endif
+#endif

+#if __UAPI_DEF_TIMEVAL
struct timeval {
__kernel_time_t tv_sec; /* seconds */
__kernel_suseconds_t tv_usec; /* microseconds */
};
+#endif

+#if __UAPI_DEF_TIMEZONE
struct timezone {
int tz_minuteswest; /* minutes west of Greenwich */
int tz_dsttime; /* type of dst correction */
};
+#endif


/*
* Names of the interval timers, and structure
* defining a timer setting:
*/
+#if __UAPI_DEF_ITIMER_WHICH
#define ITIMER_REAL 0
#define ITIMER_VIRTUAL 1
#define ITIMER_PROF 2
+#endif

+#if __UAPI_DEF_ITIMERSPEC
struct itimerspec {
struct timespec it_interval; /* timer period */
struct timespec it_value; /* timer expiration */
};
+#endif

+#if __UAPI_DEF_ITIMERVAL
struct itimerval {
struct timeval it_interval; /* timer interval */
struct timeval it_value; /* current value */
};
+#endif

/*
* The IDs of the various system clocks (for POSIX.1b interval timers):
@@ -64,6 +77,8 @@ struct itimerval {
/*
* The various flags for setting POSIX.1b interval timers:
*/
+#if __UAPI_DEF_ABSTIME
#define TIMER_ABSTIME 0x01
+#endif

#endif /* _UAPI_LINUX_TIME_H */
--
2.8.0.rc3.226.g39d4020
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