[Buildroot] [PATCH] package/ibm-sw-tpm2: re-fix build with uClibc-ng and older glibcs

Peter Korsgaard peter at korsgaard.com
Fri Aug 28 21:27:00 UTC 2020

>>>>> "Thomas" == Thomas Petazzoni <thomas.petazzoni at bootlin.com> writes:

 > In commit 26e37cef1627faa1f5ab8935482e2b2bc3465c33, 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
 > 19bd08900448aa45b506320ad2ab912f789e6e5e, 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
 > a34e7f88f67b77066f73894dc8e42bca3c076fa6.

 > However, in a34e7f88f67b77066f73894dc8e42bca3c076fa6, _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 at bootlin.com>

Committed to 2020.05.x, thanks.

Bye, Peter Korsgaard

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