fix compilation with libgc 7.0, 7.1

* configure.ac: Check for GC_pthread_exit and GC_pthread_cancel.

* libguile/gen-scmconfig.c: Write HAVE_GC_PTHREAD_CANCEL and
  HAVE_GC_PTHREAD_EXIT into scmconfig.h.

* libguile/pthread-threads.h (scm_i_pthread_exit, scm_i_pthread_cancel):
  Only redefine to their GC_pthread_* variants if we have those
  functions, which is not the case in libgc < 7.2.

configure.ac

@@ -1238,7 +1238,7 @@ save_LIBS="$LIBS"
 LIBS="$BDW_GC_LIBS $LIBS"
 CFLAGS="$BDW_GC_CFLAGS $CFLAGS"
 
-AC_CHECK_FUNCS([GC_do_blocking GC_call_with_gc_active])
+AC_CHECK_FUNCS([GC_do_blocking GC_call_with_gc_active GC_pthread_exit GC_pthread_cancel])
 
 # Though the `GC_do_blocking ()' symbol is present in GC 7.1, it is not
 # declared, and has a different type (returning void instead of

libguile/gen-scmconfig.c

@@ -318,6 +318,18 @@ main (int argc, char *argv[])
   pf ("#define SCM_NEED_BRACES_ON_PTHREAD_MUTEX_INITIALIZER %d /* 0 or 1 */\n",
       SCM_I_GSC_NEED_BRACES_ON_PTHREAD_MUTEX_INITIALIZER);
 
+#ifdef HAVE_GC_PTHREAD_CANCEL
+  pf ("#define SCM_HAVE_GC_PTHREAD_CANCEL 1 /* 0 or 1 */\n");
+#else
+  pf ("#define SCM_HAVE_GC_PTHREAD_CANCEL 0 /* 0 or 1 */\n");
+#endif
+
+#ifdef HAVE_GC_PTHREAD_EXIT
+  pf ("#define SCM_HAVE_GC_PTHREAD_EXIT 1 /* 0 or 1 */\n");
+#else
+  pf ("#define SCM_HAVE_GC_PTHREAD_EXIT 0 /* 0 or 1 */\n");
+#endif
+
   pf ("\n\n/*** File system access ***/\n");
 
   pf ("/* Define to 1 if `struct dirent64' is available.  */\n");

libguile/pthread-threads.h

@@ -38,8 +38,19 @@
 #define scm_i_pthread_self                  pthread_self
 #define scm_i_pthread_create                GC_pthread_create
 #define scm_i_pthread_detach                GC_pthread_detach
+
+#if SCM_HAVE_GC_PTHREAD_EXIT
 #define scm_i_pthread_exit                  GC_pthread_exit
+#else
+#define scm_i_pthread_exit                  pthread_exit
+#endif
+
+#if SCM_HAVE_GC_PTHREAD_CANCEL
 #define scm_i_pthread_cancel                GC_pthread_cancel
+#else
+#define scm_i_pthread_cancel                pthread_cancel
+#endif
+
 #define scm_i_pthread_cleanup_push          pthread_cleanup_push
 #define scm_i_pthread_cleanup_pop           pthread_cleanup_pop
 #define scm_i_sched_yield                   sched_yield