Re: [PATCH] libgo: check if -lucontext is required for {make,set,get}context

[Ian Lance Taylor <iant@golang.org>]

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On Mon, Dec 19, 2022 at 8:59 AM <soeren@soeren-tempel.net> wrote:
>
> From: Sören Tempel <soeren@soeren-tempel.net>
>
> This patch is similar to the existing check for librt. If libucontext
> is installed and libucontext.a provides the aforementioned symbols, then
> it is added to $LIBS. If not, no error is emitted. We could,
> alternatively, also check libc.a for these symbols and thus prefer libc
> over libucontext if both are installed and provide the symbols. If
> deemed desirable, this could be achieved by changing the invocation
> to AC_SEARCH_LIBS([makecontext], [c ucontext]).
>
> This version of this patch has been tested on x86_64 Alpine Linux Edge
> (libucontext 1.2 + musl 1.2.3) and Arch Linux (glibc 2.36). On the
> latter, the check is a no-op and $LIBS is not modified.

Thanks.  I don't see a reason to check for all the functions.
Committed like so after testing on x86_64-pc-linux-gnu with glibc.

Ian

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e1e810e2f1d4f6c45021741cb3f8d7f2be15926d
diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index d8c4e02d6e6..d123c746fb2 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-9906861dc86c1733bb304d3d45b1534adb32712c
+ecc2a2e70e44fa76a75b12d0893bc1702b72a1b4
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
diff --git a/libgo/configure b/libgo/configure
index 460fdad70a8..a607dbff68e 100755
--- a/libgo/configure
+++ b/libgo/configure
@@ -14818,6 +14818,63 @@ fi
 
 
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing makecontext" >&5
+$as_echo_n "checking for library containing makecontext... " >&6; }
+if ${ac_cv_search_makecontext+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char makecontext ();
+int
+main ()
+{
+return makecontext ();
+  ;
+  return 0;
+}
+_ACEOF
+for ac_lib in '' ucontext; do
+  if test -z "$ac_lib"; then
+    ac_res="none required"
+  else
+    ac_res=-l$ac_lib
+    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
+  fi
+  if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_search_makecontext=$ac_res
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext
+  if ${ac_cv_search_makecontext+:} false; then :
+  break
+fi
+done
+if ${ac_cv_search_makecontext+:} false; then :
+
+else
+  ac_cv_search_makecontext=no
+fi
+rm conftest.$ac_ext
+LIBS=$ac_func_search_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_makecontext" >&5
+$as_echo "$ac_cv_search_makecontext" >&6; }
+ac_res=$ac_cv_search_makecontext
+if test "$ac_res" != no; then :
+  test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
+
+fi
+
+
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing sched_yield" >&5
 $as_echo_n "checking for library containing sched_yield... " >&6; }
 if ${ac_cv_search_sched_yield+:} false; then :
diff --git a/libgo/configure.ac b/libgo/configure.ac
index 09554a37a23..a59aa091d1d 100644
--- a/libgo/configure.ac
+++ b/libgo/configure.ac
@@ -570,6 +570,9 @@ PTHREAD_LIBS=
 AC_CHECK_LIB([pthread], [pthread_create], PTHREAD_LIBS=-lpthread)
 AC_SUBST(PTHREAD_LIBS)
 
+dnl Test if -lucontext is required for makecontext.
+AC_SEARCH_LIBS([makecontext], [ucontext])
+
 dnl Test if -lrt is required for sched_yield or nanosleep or clock_gettime.
 AC_SEARCH_LIBS([sched_yield], [rt])
 AC_SEARCH_LIBS([nanosleep], [rt])