Merge branch 'rw/make-needs-librt'

Makefile assumed that -lrt is always available on platforms that
want to use clock_gettime() and CLOCK_MONOTONIC, which is not a
case for recent Mac OS X.  The necessary symbols are often found in
libc on many modern systems and having -lrt on the command line, as
long as the library exists, had no effect, but when the platform
removes librt.a that is a different matter--having -lrt will break
the linkage.

This change could be seen as a regression for those who do need to
specify -lrt, as they now specifically ask for NEEDS_LIBRT when
building. Hopefully they are in the minority these days.

* rw/make-needs-librt:
config.mak.uname: define NEEDS_LIBRT under Linux, for now
Makefile: add NEEDS_LIBRT to optionally link with librt

diff --git a/Makefile b/Makefile
index bfe85595cd0877924aa3cd3dca7b24ab17945d83..1978cb8d40b578648c05fbcfd783f9dbf2178abb 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -351,9 +351,12 @@ all::
 # Define GMTIME_UNRELIABLE_ERRORS if your gmtime() function does not
 # return NULL when it receives a bogus time_t.
 #
-# Define HAVE_CLOCK_GETTIME if your platform has clock_gettime in librt.
+# Define HAVE_CLOCK_GETTIME if your platform has clock_gettime.
 #
-# Define HAVE_CLOCK_MONOTONIC if your platform has CLOCK_MONOTONIC in librt.
+# Define HAVE_CLOCK_MONOTONIC if your platform has CLOCK_MONOTONIC.
+#
+# Define NEEDS_LIBRT if your platform requires linking with librt (glibc version
+# before 2.17) for clock_gettime and CLOCK_MONOTONIC.
 #
 # Define USE_PARENS_AROUND_GETTEXT_N to "yes" if your compiler happily
 # compiles the following initialization:
@@ -1467,13 +1470,16 @@ endif
 
 ifdef HAVE_CLOCK_GETTIME
        BASIC_CFLAGS += -DHAVE_CLOCK_GETTIME
-       EXTLIBS += -lrt
 endif
 
 ifdef HAVE_CLOCK_MONOTONIC
        BASIC_CFLAGS += -DHAVE_CLOCK_MONOTONIC
 endif
 
+ifdef NEEDS_LIBRT
+       EXTLIBS += -lrt
+endif
+
 ifdef HAVE_BSD_SYSCTL
        BASIC_CFLAGS += -DHAVE_BSD_SYSCTL
 endif

diff --git a/config.mak.uname b/config.mak.uname
index a88f13989ac9c2cbb303e2ae5f9ed43c9a5f778f..22958a8d6ffbf3ca937b5aac97bb9f616de70130 100644 (file)
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -36,6 +36,8 @@ ifeq ($(uname_S),Linux)
        HAVE_DEV_TTY = YesPlease
        HAVE_CLOCK_GETTIME = YesPlease
        HAVE_CLOCK_MONOTONIC = YesPlease
+       # -lrt is needed for clock_gettime on glibc <= 2.16
+       NEEDS_LIBRT = YesPlease
        HAVE_GETDELIM = YesPlease
        SANE_TEXT_GREP=-a
 endif