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authorFlorian Weimer <fweimer@redhat.com>2019-02-08 10:21:56 +0100
committerFlorian Weimer <fweimer@redhat.com>2019-02-08 10:43:17 +0100
commitf289e656ec8221756519a601042bc9fbe1b310fb (patch)
treed0a6ca2140f0e4a0fa34fd10ee0b0c03266fb196
parent823624bdc47f1f80109c9c52dee7939b9386d708 (diff)
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rt: Turn forwards from librt to libc into compat symbols [BZ #24194]
As the  result of commit 6e6249d0b461b952d0f544792372663feb6d792a
("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>
-rw-r--r--ChangeLog5
-rw-r--r--NEWS6
-rw-r--r--rt/clock-compat.c6
3 files changed, 14 insertions, 3 deletions
diff --git a/ChangeLog b/ChangeLog
index 29f4ac31e1..20ff76ab62 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -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]
diff --git a/NEWS b/NEWS
index e14008d7ad..45792f62a9 100644
--- a/NEWS
+++ b/NEWS
@@ -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:
 
diff --git a/rt/clock-compat.c b/rt/clock-compat.c
index c603f40b69..d8ced3cdc1 100644
--- a/rt/clock-compat.c
+++ b/rt/clock-compat.c
@@ -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,