[3.0] 282d713 Simplify libedit/readline detection somewhat.

[Tollef Fog Heen]

commit 282d713011ce70e68999eb50c779690b12cf8d3c
Author: Tollef Fog Heen <tfheen at varnish-software.com>
Date:   Tue Mar 12 14:40:21 2013 +0100

    Simplify libedit/readline detection somewhat.

diff --git a/configure.ac b/configure.ac
index 054353c..a17e139 100644
--- a/configure.ac
+++ b/configure.ac
@@ -149,15 +149,10 @@ AC_SUBST(PCRE_LIBS)
 
 PKG_CHECK_MODULES([LIBEDIT], [libedit], 
 	[AC_DEFINE([HAVE_LIBEDIT], [1], [Define we have libedit])],
-	[AC_CHECK_HEADERS([readline/readline.h])
-	 AC_CHECK_HEADERS([edit/readline/readline.h])
-	 AC_CHECK_LIB(edit, el_init,
-	        [ AC_DEFINE([HAVE_LIBEDIT], [1], [Define we have libedit])
-		  LIBEDIT_CFLAGS=""
-		  LIBEDIT_LIBS="-ledit ${CURSES_LIBS}"
-		],
-               [AC_MSG_ERROR([libedit or readline not found])],
-               [${CURSES_LIBS}])])
+	[AX_LIB_READLINE])
+if test "$ac_cv_have_readline" = no; then
+  AC_MSG_ERROR([libedit or readline not found])
+fi
 
 # Checks for header files.
 AC_HEADER_STDC
diff --git a/m4/ax_lib_readline.m4 b/m4/ax_lib_readline.m4
new file mode 100644
index 0000000..056f25c
--- /dev/null
+++ b/m4/ax_lib_readline.m4
@@ -0,0 +1,107 @@
+# ===========================================================================
+#      http://www.gnu.org/software/autoconf-archive/ax_lib_readline.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_LIB_READLINE
+#
+# DESCRIPTION
+#
+#   Searches for a readline compatible library. If found, defines
+#   `HAVE_LIBREADLINE'. If the found library has the `add_history' function,
+#   sets also `HAVE_READLINE_HISTORY'. Also checks for the locations of the
+#   necessary include files and sets `HAVE_READLINE_H' or
+#   `HAVE_READLINE_READLINE_H' and `HAVE_READLINE_HISTORY_H' or
+#   'HAVE_HISTORY_H' if the corresponding include files exists.
+#
+#   The libraries that may be readline compatible are `libedit',
+#   `libeditline' and `libreadline'. Sometimes we need to link a termcap
+#   library for readline to work, this macro tests these cases too by trying
+#   to link with `libtermcap', `libcurses' or `libncurses' before giving up.
+#
+#   Here is an example of how to use the information provided by this macro
+#   to perform the necessary includes or declarations in a C file:
+#
+#     #ifdef HAVE_LIBREADLINE
+#     #  if defined(HAVE_READLINE_READLINE_H)
+#     #    include <readline/readline.h>
+#     #  elif defined(HAVE_READLINE_H)
+#     #    include <readline.h>
+#     #  else /* !defined(HAVE_READLINE_H) */
+#     extern char *readline ();
+#     #  endif /* !defined(HAVE_READLINE_H) */
+#     char *cmdline = NULL;
+#     #else /* !defined(HAVE_READLINE_READLINE_H) */
+#       /* no readline */
+#     #endif /* HAVE_LIBREADLINE */
+#
+#     #ifdef HAVE_READLINE_HISTORY
+#     #  if defined(HAVE_READLINE_HISTORY_H)
+#     #    include <readline/history.h>
+#     #  elif defined(HAVE_HISTORY_H)
+#     #    include <history.h>
+#     #  else /* !defined(HAVE_HISTORY_H) */
+#     extern void add_history ();
+#     extern int write_history ();
+#     extern int read_history ();
+#     #  endif /* defined(HAVE_READLINE_HISTORY_H) */
+#       /* no history */
+#     #endif /* HAVE_READLINE_HISTORY */
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Ville Laurikari <vl at iki.fi>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 6
+
+AU_ALIAS([VL_LIB_READLINE], [AX_LIB_READLINE])
+AC_DEFUN([AX_LIB_READLINE], [
+  AC_CACHE_CHECK([for a readline compatible library],
+                 ax_cv_lib_readline, [
+    ORIG_LIBS="$LIBS"
+    for readline_lib in readline edit editline; do
+      for termcap_lib in "" termcap curses ncurses; do
+        if test -z "$termcap_lib"; then
+          TRY_LIB="-l$readline_lib"
+        else
+          TRY_LIB="-l$readline_lib -l$termcap_lib"
+        fi
+        LIBS="$ORIG_LIBS $TRY_LIB"
+        AC_TRY_LINK_FUNC(readline, ax_cv_lib_readline="$TRY_LIB")
+        if test -n "$ax_cv_lib_readline"; then
+          break
+        fi
+      done
+      if test -n "$ax_cv_lib_readline"; then
+        break
+      fi
+    done
+    if test -z "$ax_cv_lib_readline"; then
+      ax_cv_lib_readline="no"
+    fi
+    LIBS="$ORIG_LIBS"
+  ])
+
+  if test "$ax_cv_lib_readline" != "no"; then
+    LIBS="$LIBS $ax_cv_lib_readline"
+    AC_DEFINE(HAVE_LIBREADLINE, 1,
+              [Define if you have a readline compatible library])
+    AC_CHECK_HEADERS(readline.h readline/readline.h)
+    AC_CACHE_CHECK([whether readline supports history],
+                   ax_cv_lib_readline_history, [
+      ax_cv_lib_readline_history="no"
+      AC_TRY_LINK_FUNC(add_history, ax_cv_lib_readline_history="yes")
+    ])
+    if test "$ax_cv_lib_readline_history" = "yes"; then
+      AC_DEFINE(HAVE_READLINE_HISTORY, 1,
+                [Define if your readline library has \`add_history'])
+      AC_CHECK_HEADERS(history.h readline/history.h)
+    fi
+  fi
+])dnl