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rt: Turn forwards from librt to libc into compat symbols [BZ #24194]

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As the  result of commit 6e6249d0b4
("BZ#14743: Move clock_* symbols from librt to libc."), in glibc 2.17,
clock_gettime, clock_getres, clock_settime, clock_getcpuclockid,
clock_nanosleep were added to libc, and the file rt/clock-compat.c
was added with forwarders to the actual implementations in libc.
These forwarders were wrapped in

#if SHLIB_COMPAT (librt, GLIBC_2_2, GLIBC_2_17)

so that they are not present for newer architectures (such as
powerpc64le) with a 2.17 or later ABI baseline.  But the forwarders
were not marked as compatibility symbols.  As a result, on older
architectures, historic configure checks such as

AC_CHECK_LIB(rt, clock_gettime)

still cause linking against librt, even though this is completely
unnecessary.  It also creates a needless porting hazard because
architectures behave differently when it comes to symbol availability.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
Florian Weimer 2019-02-08 10:21:56 +01:00
parent 823624bdc4
commit f289e656ec
3 changed files with 14 additions and 3 deletions
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5
ChangeLog
View File

@ -1,3 +1,8 @@
2019-02-07 Florian Weimer <fweimer@redhat.com>
* rt/clock-compat.c (COMPAT_REDIRECT): Turn librt forwarders into
compatibility symbols.
2019-02-07 Stefan Liebler <stli@linux.ibm.com>
[BZ #24180]

6
NEWS
View File

@ -14,7 +14,11 @@ Major new features:
Deprecated and removed features, and other changes affecting compatibility:
[Add deprecations, removals and changes affecting compatibility here]
* The functions clock_gettime, clock_getres, clock_settime,
clock_getcpuclockid, clock_nanosleep were removed from the librt library
for new applications (on architectures which had them). Instead, the
definitions in libc will be used automatically, which have been available
since glibc 2.17.
Changes to build and runtime requirements:

6
rt/clock-compat.c
View File

@ -30,14 +30,16 @@
#if HAVE_IFUNC
# undef INIT_ARCH
# define INIT_ARCH()
# define COMPAT_REDIRECT(name, proto, arglist) libc_ifunc (name, &__##name)
# define COMPAT_REDIRECT(name, proto, arglist) libc_ifunc (name, &__##name) \
compat_symbol (librt, name, name, GLIBC_2_2);
#else
# define COMPAT_REDIRECT(name, proto, arglist) \
int \
name proto \
{ \
return __##name arglist; \
}
} \
compat_symbol (librt, name, name, GLIBC_2_2);
#endif
COMPAT_REDIRECT (clock_getres,