Tighten host Scheme detection in configure script.

Now the script requires MIT_SCHEME_EXE to work if it is set, in order
to detect early the legitimate error of setting it wrong.

diff --git a/src/configure.ac b/src/configure.ac
index 30eb1cd43d19d77a3b791a47069d510bdfa546c8..e69034273e027839405f08894f601b2d652b1bab 100644 (file)
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -77,18 +77,48 @@ AUXDIR='$(libdir)'/${AUXDIR_NAME}
 #   src/configure.ac
 #   src/etc/make-native.sh
 
-: ${MIT_SCHEME_EXE:=mit-scheme-${mit_scheme_native_code}}
 if test x"${enable_host_scheme_test}" = xyes; then
     AC_MSG_CHECKING([for an existing MIT/GNU Scheme installation])
-    if "${MIT_SCHEME_EXE}" --batch-mode --eval '(%exit)' >/dev/null 2>&1; then
-       :
+    # Kinda hairy logic to detect this: (1) Use MIT_SCHEME_EXE, and
+    # don't try to detect anything automagically, if it's set -- this
+    # will make broken scripts that set MIT_SCHEME_EXE brokenly fail
+    # early.  (2) Otherwise, use mit-scheme-ARCH if we can, because
+    # it's guaranteed to have the right compiler.  (3) Try mit-scheme
+    # if that fails.  (Will mit-scheme and not mit-scheme-ARCH ever be
+    # the right thing?)
+    found_p=no
+    env_p=no
+    native_exe="mit-scheme-${mit_scheme_native_code}"
+    if test x"${MIT_SCHEME_EXE:+set}" = xset; then
+       env_p=yes
+       if "${MIT_SCHEME_EXE}" --batch-mode --eval '(%exit)' >/dev/null 2>&1;
+       then
+           found_p=yes
+       fi
+    elif "${native_exe}" --batch-mode --eval '(%exit)' >/dev/null 2>&1; then
+       MIT_SCHEME_EXE="${native_exe}"
+       found_p=yes
     elif mit-scheme --batch-mode --eval '(%exit)' >/dev/null 2>&1; then
        MIT_SCHEME_EXE=mit-scheme
+       found_p=yes
+    fi
+    if test x"${found_p}" = xyes; then
+       AC_MSG_RESULT([yes])
     else
+       message=
+       if test x"${env_p}" = xyes; then
+           message="the MIT_SCHEME_EXE environment variable does not run it:
+
+   MIT_SCHEME_EXE=${MIT_SCHEME_EXE}"
+       else
+           message="the following programs do not run it:
+
+   mit-scheme-${mit_scheme_native_code}
+   mit-scheme"
+       fi
        AC_MSG_ERROR([
 This script needs an existing MIT/GNU Scheme installation to function,
-but neither the program \`${MIT_SCHEME_EXE}' nor the program
-\`mit-scheme' appears to run it.
+but ${message}
 
 If you have installed MIT/GNU Scheme in an unusual location, set the
 environment variable MIT_SCHEME_EXE to the name or pathname of the
@@ -98,7 +128,6 @@ MITSCHEME_LIBRARY_PATH to the pathname of the MIT/GNU Scheme library
 directory, which is usually \`/usr/local/lib/mit-scheme-${mit_scheme_native_code}'.
 ])
     fi
-    AC_MSG_RESULT([yes])
 fi
 
 AC_SUBST([ALL_TARGET])