[PATCH] socklen: do not depend on sys_socket

[Paul Eggert]

Here's another Emacs-related patch I'm proposing for gnulib
to break an unnecessary dependency, in this case a circular one.

----

While trying to modify Emacs to use gnulib's socklen module,
I discovered a circular dependency: socklen depends on sys_socket
and vice versa.  Emacs can use socklen, but it does not need
sys_socket because Emacs is not intended to be portable to
MingW and Cygwin.
* m4/socklen.m4 (gl_PREREQ_TYPE_SOCKLEN_T): New macro, taken from
parts of gl_PREREQ_SYS_H_SOCKET.
(gl_TYPE_SOCKLEN_T): Require it instead of requiring
gl_PREREQ_SYS_H_SOCKET.  Check for ws2tcpip.h only if
sys_socket is also used.
* m4/sys_socket_h.m4 (gl_PREREQ_SYS_H_SOCKET): Require
gl_PREREQ_TYPE_SOCKLEN_T instead of doing its work ourselves.
* modules/inet_ntop (Depends-on): Remove socklen, since
sys_socket is supposed to provide socklen_t and we already
depend on sys_socket.
* modules/inet_pton, modules/netdb: Likewise.
* modules/socklen: Do not depend on sys_socket.
---
 ChangeLog          |   21 +++++++++++++++++++++
 m4/socklen.m4      |   26 +++++++++++++++++++-------
 m4/sys_socket_h.m4 |    9 ++-------
 modules/inet_ntop  |    1 -
 modules/inet_pton  |    1 -
 modules/netdb      |    1 -
 modules/socklen    |    1 -
 7 files changed, 42 insertions(+), 18 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 917e834..199db7b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,24 @@
+2011-03-16  Paul Eggert  <address@hidden>
+
+       socklen: do not depend on sys_socket
+       While trying to modify Emacs to use gnulib's socklen module,
+       I discovered a circular dependency: socklen depends on sys_socket
+       and vice versa.  Emacs can use socklen, but it does not need
+       sys_socket because Emacs is not intended to be portable to
+       MingW and Cygwin.
+       * m4/socklen.m4 (gl_PREREQ_TYPE_SOCKLEN_T): New macro, taken from
+       parts of gl_PREREQ_SYS_H_SOCKET.
+       (gl_TYPE_SOCKLEN_T): Require it instead of requiring
+       gl_PREREQ_SYS_H_SOCKET.  Check for ws2tcpip.h only if
+       sys_socket is also used.
+       * m4/sys_socket_h.m4 (gl_PREREQ_SYS_H_SOCKET): Require
+       gl_PREREQ_TYPE_SOCKLEN_T instead of doing its work ourselves.
+       * modules/inet_ntop (Depends-on): Remove socklen, since
+       sys_socket is supposed to provide socklen_t and we already
+       depend on sys_socket.
+       * modules/inet_pton, modules/netdb: Likewise.
+       * modules/socklen: Do not depend on sys_socket.
+
 2011-03-16  Jim Meyering  <address@hidden>
 
        maint.mk: allow fine-grained syntax-check exclusion via Make variables
diff --git a/m4/socklen.m4 b/m4/socklen.m4
index 5e4c69e..28dcf07 100644
--- a/m4/socklen.m4
+++ b/m4/socklen.m4
@@ -1,4 +1,4 @@
-# socklen.m4 serial 8
+# socklen.m4 serial 9
 dnl Copyright (C) 2005-2007, 2009-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -14,10 +14,10 @@ dnl So we have to test to find something that will work.
 
 dnl On mingw32, socklen_t is in ws2tcpip.h ('int'), so we try to find
 dnl it there first.  That file is included by gnulib's sys_socket.in.h, which
-dnl all users of this module should include.  Cygwin must not include
-dnl ws2tcpip.h.
+dnl all users of this module should include if they want to be portable to
+dnl mingw32.  Cygwin must not include ws2tcpip.h.
 AC_DEFUN([gl_TYPE_SOCKLEN_T],
-  [AC_REQUIRE([gl_HEADER_SYS_SOCKET])dnl
+  [AC_REQUIRE([gl_PREREQ_TYPE_SOCKLEN_T])dnl
    AC_CHECK_TYPE([socklen_t], ,
      [AC_MSG_CHECKING([for socklen_t equivalent])
       AC_CACHE_VAL([gl_cv_socklen_t_equiv],
@@ -48,6 +48,18 @@ AC_DEFUN([gl_TYPE_SOCKLEN_T],
      [#include <sys/types.h>
       #if HAVE_SYS_SOCKET_H
       # include <sys/socket.h>
-      #elif HAVE_WS2TCPIP_H
-      # include <ws2tcpip.h>
-      #endif])])
+      ]m4_ifdef([gl_SYS_SOCKET_H_DEFAULTS],
+         [#elif HAVE_WS2TCPIP_H
+          # include <ws2tcpip.h>]
+      )[#endif])])
+
+AC_DEFUN([gl_PREREQ_TYPE_SOCKLEN_T],
+  [AC_CHECK_HEADERS_ONCE([sys/socket.h])
+   m4_ifdef([gl_SYS_SOCKET_H_DEFAULTS],
+     [if test $ac_cv_header_sys_socket_h = no; then
+        dnl We cannot use AC_CHECK_HEADERS_ONCE here, because that would make
+        dnl the check for those headers unconditional; yet cygwin reports
+        dnl that the headers are present but cannot be compiled (since on
+        dnl cygwin, all socket information should come from sys/socket.h).
+        AC_CHECK_HEADERS([ws2tcpip.h])
+      fi])])
diff --git a/m4/sys_socket_h.m4 b/m4/sys_socket_h.m4
index 12dc05d..0ba6109 100644
--- a/m4/sys_socket_h.m4
+++ b/m4/sys_socket_h.m4
@@ -1,4 +1,4 @@
-# sys_socket_h.m4 serial 21
+# sys_socket_h.m4 serial 22
 dnl Copyright (C) 2005-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -101,17 +101,12 @@ AC_DEFUN([gl_HEADER_SYS_SOCKET],
 AC_DEFUN([gl_PREREQ_SYS_H_SOCKET],
 [
   dnl Check prerequisites of the <sys/socket.h> replacement.
-  gl_CHECK_NEXT_HEADERS([sys/socket.h])
+  AC_REQUIRE([gl_PREREQ_TYPE_SOCKLEN_T])
   if test $ac_cv_header_sys_socket_h = yes; then
     HAVE_SYS_SOCKET_H=1
     HAVE_WS2TCPIP_H=0
   else
     HAVE_SYS_SOCKET_H=0
-    dnl We cannot use AC_CHECK_HEADERS_ONCE here, because that would make
-    dnl the check for those headers unconditional; yet cygwin reports
-    dnl that the headers are present but cannot be compiled (since on
-    dnl cygwin, all socket information should come from sys/socket.h).
-    AC_CHECK_HEADERS([ws2tcpip.h])
     if test $ac_cv_header_ws2tcpip_h = yes; then
       HAVE_WS2TCPIP_H=1
     else
diff --git a/modules/inet_ntop b/modules/inet_ntop
index c6a1b80..3b00b62 100644
--- a/modules/inet_ntop
+++ b/modules/inet_ntop
@@ -6,7 +6,6 @@ lib/inet_ntop.c
 m4/inet_ntop.m4
 
 Depends-on:
-socklen
 sys_socket
 arpa_inet
 errno
diff --git a/modules/inet_pton b/modules/inet_pton
index 271d778..44c50b8 100644
--- a/modules/inet_pton
+++ b/modules/inet_pton
@@ -7,7 +7,6 @@ m4/inet_pton.m4
 
 Depends-on:
 c-ctype
-socklen
 sys_socket
 arpa_inet
 errno
diff --git a/modules/netdb b/modules/netdb
index ea7dc63..9b95a6e 100644
--- a/modules/netdb
+++ b/modules/netdb
@@ -10,7 +10,6 @@ include_next
 arg-nonnull
 warn-on-use
 sys_socket
-socklen
 
 configure.ac:
 gl_HEADER_NETDB
diff --git a/modules/socklen b/modules/socklen
index 4986f10..bc1236f 100644
--- a/modules/socklen
+++ b/modules/socklen
@@ -5,7 +5,6 @@ Files:
 m4/socklen.m4
 
 Depends-on:
-sys_socket
 
 configure.ac:
 gl_TYPE_SOCKLEN_T
-- 
1.7.4