pthread_sigmask: Document MidnightBSD bug

[Bruno Haible]

The result of configure tests on MidnightBSD 1.1 shows that this platform
has the same bug as earlier FreeBSD versions. This patch documents it.


2021-02-07  Bruno Haible  <bruno@clisp.org>

        pthread_sigmask: Document MidnightBSD bug.
        * doc/posix-functions/pthread_sigmask.texi: Mention MidnightBSD as an
        affected platform.
        * m4/pthread_sigmask.m4 (gl_FUNC_PTHREAD_SIGMASK): Update
        cross-compilation guess accordingly.

diff --git a/doc/posix-functions/pthread_sigmask.texi 
b/doc/posix-functions/pthread_sigmask.texi
index 2814662..aefe0a9 100644
--- a/doc/posix-functions/pthread_sigmask.texi
+++ b/doc/posix-functions/pthread_sigmask.texi
@@ -18,7 +18,7 @@ FreeBSD 6.4, OpenBSD 3.8.
 @item
 This function does nothing and always returns 0 in programs that are not
 linked with @code{-lpthread} on some platforms:
-FreeBSD 6.4, HP-UX 11.31, Solaris 9.
+FreeBSD 6.4, MidnightBSD 1.1, HP-UX 11.31, Solaris 9.
 @item
 When it fails, this functions returns @minus{}1 instead of the error number on
 some platforms:
diff --git a/m4/pthread_sigmask.m4 b/m4/pthread_sigmask.m4
index eb4c784..7c74415 100644
--- a/m4/pthread_sigmask.m4
+++ b/m4/pthread_sigmask.m4
@@ -1,4 +1,4 @@
-# pthread_sigmask.m4 serial 19
+# pthread_sigmask.m4 serial 20
 dnl Copyright (C) 2011-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -111,9 +111,9 @@ AC_DEFUN([gl_FUNC_PTHREAD_SIGMASK],
     AC_REQUIRE([AC_PROG_CC])
     AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
 
-    dnl On FreeBSD 6.4, HP-UX 11.31, Solaris 9, in programs that are not linked
-    dnl with -lpthread, the pthread_sigmask() function always returns 0 and has
-    dnl no effect.
+    dnl On FreeBSD 6.4, MidnightBSD 1.1, HP-UX 11.31, Solaris 9, in programs
+    dnl that are not linked with -lpthread, the pthread_sigmask() function
+    dnl always returns 0 and has no effect.
     if test -z "$LIB_PTHREAD_SIGMASK"; then
       case " $LIBS " in
         *' -pthread '*) ;;
@@ -138,7 +138,7 @@ AC_DEFUN([gl_FUNC_PTHREAD_SIGMASK],
                 [
                  changequote(,)dnl
                  case "$host_os" in
-                   freebsd* | hpux* | solaris | solaris2.[2-9]*)
+                   freebsd* | midnightbsd* | hpux* | solaris | solaris2.[2-9]*)
                      gl_cv_func_pthread_sigmask_in_libc_works="guessing no";;
                    *)
                      gl_cv_func_pthread_sigmask_in_libc_works="guessing yes";;