Enable including 'readline' from a non standard location.

--with-readline=<location> may be given instead of --with-readline=yes
This is required when on macOS readline is installed from Homebrew.
Standard Xcode readline in macOS is not compatible with ngspice.
If --with-readline=yes is given, there is no change of behaviour
compared with previous releases.

compile_macos.sh

@@ -51,14 +51,14 @@ if test "$1" = "d"; then
   echo
 # You may add  --enable-adms to the following command for adding adms generated devices
 # builtin readline not compatible (Big Sur), readline via Homebrew required (in /usr/local/opt)
-  ../configure --with-x --enable-xspice --enable-cider --with-readline=/usr/local/opt --enable-openmp CFLAGS="-m64 -O0 -g -Wall -I/opt/X11/include/freetype2" LDFLAGS="-m64 -lomp -g"
+  ../configure --with-x --enable-xspice --enable-cider --with-readline=/usr/local/opt/readline --enable-openmp CFLAGS="-m64 -O0 -g -Wall -I/opt/X11/include/freetype2 -I/usr/local/opt/readline/include" LDFLAGS="-m64 -lomp -g -L/usr/local/opt/readline/lib"
 else
    cd release
    if [ $? -ne 0 ]; then  echo "cd release failed"; exit 1 ; fi
   echo "configuring for 64 bit release"
   echo
 # You may add  --enable-adms to the following command for adding adms generated devices
-  ../configure --with-x --enable-xspice --enable-cider --with-readline=/usr/local/opt --enable-openmp --disable-debug CFLAGS="-m64 -O2 -I/opt/X11/include/freetype2" LDFLAGS="-m64 -lomp"
+  ../configure --with-x --enable-xspice --enable-cider --with-readline=/usr/local/opt/readline --enable-openmp --disable-debug CFLAGS="-m64 -O2 -I/opt/X11/include/freetype2 -I/usr/local/opt/readline/include" LDFLAGS="-m64 -lomp -L/usr/local/opt/readline/lib"
 fi
 if [ $? -ne 0 ]; then  echo "../configure failed"; exit 1 ; fi
 

configure.ac

@@ -1161,24 +1161,43 @@ fi
 #  ----  Default: disabled.                                     ----
 #  ----  Hope to see in the future readline replacement.        ----
 
-if test "x$with_readline" != xyes; then
+if test "x$with_readline" = x  ||  test "x$with_readline" = xno ; then
     AC_MSG_RESULT([GNU readline disabled.])
 else
-    if test "x$with_tcl" = x  ||  test "x$with_tcl" = xno ; then
-        AC_MSG_RESULT([Checking for readline:])
-        AC_CHECK_HEADERS([readline/readline.h readline/history.h],
-            [AC_DEFINE([HAVE_GNUREADLINE], [], [Define if we have GNU readline])],
-            [AC_MSG_ERROR([Couldn't find GNU readline headers.])])
-        AC_SEARCH_LIBS([tputs], [ncurses tinfo termcap],
-            [AC_DEFINE([HAVE_TERMCAP], [], [Define if we have ncurses/terminfo or termcap])],
-            [AC_MSG_ERROR([Found neither ncurses/terminfo or termcap])])
-        AC_CHECK_LIB([readline], [readline],
-            [LIBS="$LIBS -lreadline"],
-            [AC_MSG_ERROR([Couldn't find readline libraries.])])
+    if test "x$with_readline" = xyes; then
+        if test "x$with_tcl" = x  ||  test "x$with_tcl" = xno ; then
+            AC_MSG_RESULT([Checking for readline:])
+            AC_CHECK_HEADERS([readline/readline.h readline/history.h],
+                [AC_DEFINE([HAVE_GNUREADLINE], [], [Define if we have GNU readline])],
+                [AC_MSG_ERROR([Couldn't find GNU readline headers.])])
+            AC_SEARCH_LIBS([tputs], [ncurses tinfo termcap],
+                [AC_DEFINE([HAVE_TERMCAP], [], [Define if we have ncurses/terminfo or termcap])],
+                [AC_MSG_ERROR([Found neither ncurses/terminfo or termcap])])
+            AC_CHECK_LIB([readline], [readline],
+                [LIBS="$LIBS -lreadline"],
+                [AC_MSG_ERROR([Couldn't find readline libraries.])])
+        fi
+    else
+# Especially defined for macOS (Big Sur), with readline installed from Brew
+        for dir in \
+            $with_readline
+            do
+                if test "x$with_tcl" = x  ||  test "x$with_tcl" = xno ; then
+                    AC_MSG_RESULT([Checking for readline:])
+                    AC_CHECK_HEADERS([$dir/include/readline/readline.h $dir/include/readline/history.h],
+                        [AC_DEFINE([HAVE_GNUREADLINE], [], [Define if we have GNU readline])],
+                        [AC_MSG_ERROR([Couldn't find GNU readline headers.])])
+                    AC_SEARCH_LIBS([tputs], [ncurses tinfo termcap],
+                        [AC_DEFINE([HAVE_TERMCAP], [], [Define if we have ncurses/terminfo or termcap])],
+                        [AC_MSG_ERROR([Found neither ncurses/terminfo or termcap])])
+                    AC_CHECK_LIB([readline], [readline],
+                        [LIBS="$LIBS -lreadline"],
+                        [AC_MSG_ERROR([Couldn't find readline libraries.])])
+                fi
+            done
     fi
 fi
 
-
 #  ----  Option to include BSD editline support in ngspice CLI  ----
 #  ----  Default: disabled.                                     ----