gccgo: link static libgo against -lrt on GNU/Linux

The upcoming Go 1.18 release requires linking against -lrt on GNU/Linux
(only) in order to call timer_create and friends.

Also change gotools to link the runtime test against -lrt.

	* gospec.cc (RTLIB, RT_LIBRARY): Define.
	(lang_specific_driver): Add -lrt if linking statically on
	GNU/Linux.

	* configure.ac (RT_LIBS): Define.
	* Makefile.am (check-runtime): Set GOLIBS to $(RT_LIBS).
	* configure, Makefile.in: Regenerate.

1 files changed, 37 insertions, 5 deletions

diff --git a/gcc/go/gospec.cc b/gcc/go/gospec.cc
index df92b62..ba7ba4e 100644
--- a/gcc/go/gospec.cc
+++ b/gcc/go/gospec.cc
@@ -29,10 +29,12 @@ along with GCC; see the file COPYING3.  If not see
 #define MATHLIB		(1<<2)
 /* This bit is set if they did `-lpthread'.  */
 #define THREADLIB	(1<<3)
+/* This bit is set if they did `-lrt'.  */
+#define RTLIB		(1<<4)
 /* This bit is set if they did `-lc'.  */
-#define WITHLIBC	(1<<4)
+#define WITHLIBC	(1<<5)
 /* Skip this option.  */
-#define SKIPOPT		(1<<5)
+#define SKIPOPT		(1<<6)
 
 #ifndef MATH_LIBRARY
 #define MATH_LIBRARY "m"
@@ -44,6 +46,8 @@ along with GCC; see the file COPYING3.  If not see
 #define THREAD_LIBRARY "pthread"
 #define THREAD_LIBRARY_PROFILE THREAD_LIBRARY
 
+#define RT_LIBRARY "rt"
+
 #define LIBGO "go"
 #define LIBGO_PROFILE LIBGO
 #define LIBGOBEGIN "gobegin"
@@ -74,6 +78,9 @@ lang_specific_driver (struct cl_decoded_option **in_decoded_options,
   /* "-lpthread" if it appears on the command line.  */
   const struct cl_decoded_option *saw_thread = 0;
 
+  /* "-lrt" if it appears on the command line.  */
+  const struct cl_decoded_option *saw_rt = 0;
+
   /* "-lc" if it appears on the command line.  */
   const struct cl_decoded_option *saw_libc = 0;
 
@@ -84,6 +91,9 @@ lang_specific_driver (struct cl_decoded_option **in_decoded_options,
   /* Whether we need the thread library.  */
   int need_thread = 0;
 
+  /* Whether we need the rt library.  */
+  int need_rt = 0;
+
   /* By default, we throw on the math library if we have one.  */
   int need_math = (MATH_LIBRARY[0] != '\0');
 
@@ -156,6 +166,8 @@ lang_specific_driver (struct cl_decoded_option **in_decoded_options,
 	    }
 	  else if (strcmp (arg, THREAD_LIBRARY) == 0)
 	    args[i] |= THREADLIB;
+	  else if (strcmp (arg, RT_LIBRARY) == 0)
+	    args[i] |= RTLIB;
 	  else if (strcmp (arg, "c") == 0)
 	    args[i] |= WITHLIBC;
 	  else
@@ -260,7 +272,7 @@ lang_specific_driver (struct cl_decoded_option **in_decoded_options,
 #endif
 
   /* Make sure to have room for the trailing NULL argument.  */
-  num_args = argc + need_math + shared_libgcc + (library > 0) * 5 + 10;
+  num_args = argc + need_math + shared_libgcc + (library > 0) * 6 + 10;
   new_decoded_options = XNEWVEC (struct cl_decoded_option, num_args);
 
   i = 0;
@@ -314,6 +326,12 @@ lang_specific_driver (struct cl_decoded_option **in_decoded_options,
 	  saw_thread = &decoded_options[i];
 	}
 
+      if (!saw_rt && (args[i] & RTLIB) && library > 0)
+	{
+	  --j;
+	  saw_rt = &decoded_options[i];
+	}
+
       if (!saw_libc && (args[i] & WITHLIBC) && library > 0)
 	{
 	  --j;
@@ -395,9 +413,23 @@ lang_specific_driver (struct cl_decoded_option **in_decoded_options,
 #endif
 
       /* When linking libgo statically we also need to link with the
-	 pthread library.  */
+	 pthread and (on GNU/Linux) the rt library.  */
       if (library > 1 || static_link)
-	need_thread = 1;
+	{
+	  need_thread = 1;
+	  if (strstr (DEFAULT_TARGET_MACHINE, "linux") != NULL)
+	    need_rt = 1;
+	}
+    }
+
+  if (saw_rt)
+    new_decoded_options[j++] = *saw_rt;
+  else if (library > 0 && need_rt)
+    {
+      generate_option (OPT_l, RT_LIBRARY, 1, CL_DRIVER,
+		       &new_decoded_options[j]);
+      added_libraries++;
+      j++;
     }
 
   if (saw_thread)