cross compiling and autoconf's host vs build (vs target)

The autoconf 2.13 to 2.50 transition, er, "cleaned up" cross
compilation and, in the process, "clarified" the meaning of "host",
"build" and "target".

For instance, I can specify:

./configure --host=m68k-uclinux-linux --build=i686-pc-linux-gnu
--target=m68k-uclinux-linux ...

to cross compile npsr (--host and host!=build trigger the cross compile):

checking build system type... i686-pc-linux-gnu
checking host system type... m68k-uclinux-linux-gnu
checking target system type... m68k-uclinux-linux-gnu

However, for nspr, this didn't work.  Looking at configure.in, it
seems to still have traces of the old 2.13 conventions (mixing "$host"
and "$build").  For instance:

-if test "$target" != "$host"; then
-    echo "cross compiling from $host to $target"
+if test "$target" != "$build"; then
+    echo "cross compiling from $build to $target"

which is changed by the below patch.

However, tread carefully, I find the way this all hangs together
quickly gets messy and confusing (details are in "Hosts and
Cross-Compilation" section in autoconf's documentation).

Andrew

--- nspr-4.10.10/nspr/configure.in.orig    2015-11-26 10:15:40.436090828 -0500
+++ nspr-4.10.10/nspr/configure.in    2015-11-26 10:17:44.593081097 -0500
@@ -552,8 +552,8 @@
 dnl ========================================================
 dnl Checks for compilers.
 dnl ========================================================
-if test "$target" != "$host"; then
-    echo "cross compiling from $host to $target"
+if test "$target" != "$build"; then
+    echo "cross compiling from $build to $target"
     cross_compiling=yes

     case "$build:$target" in
@@ -582,7 +582,7 @@
 AC_PROG_CC

 dnl Reenter the conditional blocks after invoking AC_PROG_CC.
-if test "$target" != "$host"; then
+if test "$target" != "$build"; then
     if test -n "$USE_CPLUS"; then
         AC_CHECK_PROGS(CXX, $CXX "${target_alias}-g++" "${target}-g++", echo)
         unset ac_cv_prog_CXX
@@ -610,7 +610,7 @@
     _SAVE_CFLAGS="$CFLAGS"
     _SAVE_LDFLAGS="$LDFLAGS"

-    AC_MSG_CHECKING([for $host compiler])
+    AC_MSG_CHECKING([for $build compiler])
     AC_CHECK_PROGS(HOST_CC, $HOST_CC gcc cc /usr/ucb/cc, "")
     if test -z "$HOST_CC"; then
         AC_MSG_ERROR([no acceptable cc found in \$PATH])
@@ -621,10 +621,10 @@
     CFLAGS="$HOST_CFLAGS"
     LDFLAGS="$HOST_LDFLAGS"

-    AC_MSG_CHECKING([whether the $host compiler ($HOST_CC
$HOST_CFLAGS $HOST_LDFLAGS) works])
+    AC_MSG_CHECKING([whether the $build compiler ($HOST_CC
$HOST_CFLAGS $HOST_LDFLAGS) works])
     AC_TRY_COMPILE([], [return 0;],
         [AC_MSG_RESULT([yes])],
-        [AC_MSG_ERROR([installation or configuration problem: $host
compiler $HOST_CC cannot create executables.])] )
+        [AC_MSG_ERROR([installation or configuration problem: $build
compiler $HOST_CC cannot create executables.])] )

     CC=$_SAVE_CC
     CFLAGS=$_SAVE_CFLAGS
@@ -1163,9 +1163,9 @@
 fi

 dnl ========================================================
-dnl Override of system specific host options
+dnl Override of system specific build options
 dnl ========================================================
-case "$host" in
+case "$build" in
 *-mingw*|*-msys*)
     NSINSTALL=nsinstall
     ;;