In commit 26e37cef16, we started using
__WORDSIZE to get the size of longs on the given architecture, in
order to support all CPU architectures.
Unfortunately, __WORDSIZE is not enabled in musl, so in
19bd089004, we switched to using
LONG_BIT instead of __WORDSIZE.
However, LONG_BIT is not readily available on glibc, you need
_XOPEN_SOURCE to be defined, which was done in
a34e7f88f6.
However, in a34e7f88f6, _XOPEN_SOURCE
was just defined, with no specific value. This caused the build to
break again on uClibc-ng and older glibcs, because clock_gettime() and
CLOCK_MONOTONIC were no longer defined. In both uClibc-ng and glibc,
CLOCK_MONOTONIC is only defined if __USE_POSIX199309 is defined. It
turns out that simply defining _XOPEN_SOURCE with no value does not
lead to __USE_POSIX199309 being defined in uClibc-ng and old glibcs,
while it is defined in newer glibcs.
The difference comes from the following snippet of code, which is
present in recent enough glibc's <feature.h> but not uClibc-ng's or
older glibc's <feature.h>:
/* If none of the ANSI/POSIX macros are defined, or if _DEFAULT_SOURCE
is defined, use POSIX.1-2008 (or another version depending on
_XOPEN_SOURCE). */
So the fact that we are defining _DEFAULT_SOURCE makes it assume that
we're using POSIX 2008.09, which obviously includes POSIX 1993.09.
Due to the lack of this code snippet, uClibc-ng <features.h> only
enables:
!defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE)
but not:
So we need an _XOPEN_SOURCE level of at least 500 for POSIX 1993.09
definitions to be available.
This is confirmed by the feature_test_macros man page, which states:
_XOPEN_SOURCE < 500
_POSIX_C_SOURCE is defined with the value 2.
500 <= _XOPEN_SOURCE < 600
_POSIX_C_SOURCE is defined with the value 199506L.
When this is fixed, another issue arises with older glibc toolchains
(such as Sourcery ARM), where fd_set is no longer defined. Inded, with
POSIX-1.2001 being enabled, we need to include <sys/select.h> to
access the fd_set definition and friends (see man fd_set for details).
This commit was tested with two glibc toolchains (recent and old), one
uClibc-ng toolchain and one musl toolchain.
Fixes:
http://autobuild.buildroot.net/results/e20f9474fc0217036faa6561df33fa983466ddfe/
(uClibc-ng)
http://autobuild.buildroot.net/results/b5d944389fc96ef2c5e0608fe4ac34149e5f9739/
(glibc)
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Acked-by: Vincent Fazio <vfazio@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
dac45969b6