build: remove linking librt for backwards compatibility

fanquake · fanquake · commit f7453dcc0386 · 2019-12-31T21:58:00.000+03:00
Now that we require glibc 2.17+, #17538, we can remove linking in librt for backwards compatibility purposes. The clock_* functions from librt were merged into glibc as part of the 2.17 release. * The `clock_*' suite of functions (declared in <time.h>) is now available directly in the main C library. Previously it was necessary to link with -lrt to use these functions. This change has the effect that a single-threaded program that uses a function such as `clock_gettime' (and is not linked with -lrt) will no longer implicitly load the pthreads library at runtime and so will not suffer the overheads associated with multi-thread support in other code such as the C++ runtime library. https://sourceware.org/ml/libc-announce/2012/msg00001.html Note that librt is already not linked by the RISC-V and AARCH64 binaries.
diff --git a/build_msvc/bitcoin_config.h b/build_msvc/bitcoin_config.h
@@ -218,9 +218,6 @@
 /* Define to 1 if you have the `rpcrt4' library (-lrpcrt4). */
 #define HAVE_LIBRPCRT4 1
 
-/* Define to 1 if you have the `rt' library (-lrt). */
-/* #undef HAVE_LIBRT */
-
 /* Define to 1 if you have the `shell32' library (-lshell32). */
 #define HAVE_LIBSHELL32 1
 
diff --git a/configure.ac b/configure.ac
@@ -693,10 +693,6 @@ AX_GCC_FUNC_ATTRIBUTE([dllimport])
 
 if test x$use_glibc_compat != xno; then
 
-  dnl glibc absorbed clock_gettime in 2.17. librt (its previous location) is safe to link
-  dnl in anyway for back-compat.
-  AC_CHECK_LIB([rt],[clock_gettime],, AC_MSG_ERROR(librt missing))
-
   dnl __fdelt_chk's params and return type have changed from long unsigned int to long int.
   dnl See which one is present here.
   AC_MSG_CHECKING(__fdelt_chk type)
