From: Helmut Grohne <helmut@subdivi.de>
Subject: make cross compilation work

This patch essentially replaces most AC_TRY_RUN with something "better".
Dependening on the use case that may be AC_TRY_COMPILE, AC_COMPUTE_INT or even
AC_CHECK_TYPE. Uses beyond cross compilation:
 * Significant simplification of the code.
 * Some checks become cacheable.

Index: expect-5.45/configure.in
===================================================================
--- expect-5.45.orig/configure.in
+++ expect-5.45/configure.in
@@ -467,47 +467,32 @@
 # and if so that WNOHANG is not defined.  The only place I've
 # seen this is ISC.
 AC_MSG_CHECKING([if WNOHANG requires _POSIX_SOURCE])
-AC_TRY_RUN([
+AC_TRY_COMPILE([
 #include <sys/wait.h>
-main() {
+],[
 #ifndef WNOHANG
-	return 0;
-#else
-	return 1;
+#error WNOHANG missing
 #endif
-}],
-	AC_MSG_RESULT(yes)
-	AC_DEFINE(WNOHANG_REQUIRES_POSIX_SOURCE)
-,
+],
 	AC_MSG_RESULT(no)
 ,
-	AC_MSG_ERROR([Expect can't be cross compiled])
+	AC_MSG_RESULT(yes)
+	AC_DEFINE(WNOHANG_REQUIRES_POSIX_SOURCE)
 )
 
 AC_MSG_CHECKING([if any value exists for WNOHANG])
 rm -rf wnohang
-AC_TRY_RUN([
+AC_COMPUTE_INT(WNOHANG_BACKUP_VALUE, WNOHANG, [
 #include <stdio.h>
 #include <sys/wait.h>
-main() {
-#ifdef WNOHANG
-	FILE *fp = fopen("wnohang","w");
-	fprintf(fp,"%d",WNOHANG);
-	fclose(fp);
-	return 0;
-#else
-	return 1;
-#endif
-}],
-	AC_MSG_RESULT(yes)
-	AC_DEFINE_UNQUOTED(WNOHANG_BACKUP_VALUE, `cat wnohang`)
-	rm -f wnohang
-,
-	AC_MSG_RESULT(no)
+],[WNOHANG_BACKUP_VALUE=no])
+if "$WNOHANG_BACKUP_VALUE" = "no"; then
 	AC_DEFINE(WNOHANG_BACKUP_VALUE, 1)
-,
-	AC_MSG_ERROR([Expect can't be cross compiled])
-)
+	AC_MSG_RESULT(no)
+else
+	AC_DEFINE_UNQUOTED(WNOHANG_BACKUP_VALUE, [$WNOHANG_BACKUP_VALUE])
+	AC_MSG_RESULT(yes)
+fi
 
 #
 # check how signals work
@@ -711,22 +696,12 @@
 fi
 
 # first check for the pure bsd
-AC_MSG_CHECKING([for struct sgttyb])
-AC_TRY_RUN([
-#include <sgtty.h>
-main()
-{
-  struct sgttyb tmp;
-  exit(0);
-}],
-        AC_MSG_RESULT(yes)
+AC_CHECK_TYPE([struct sgttyb],[
         AC_DEFINE(HAVE_SGTTYB)
         PTY_TYPE=sgttyb
-,
-        AC_MSG_RESULT(no)
-,
-	AC_MSG_ERROR([Expect can't be cross compiled])
-)
+],[],[
+#include <sgtty.h>
+])
 
 # mach systems have include files for unimplemented features
 # so avoid doing following test on those systems
@@ -736,109 +711,77 @@
   # note that if we detect termio.h (only), we still set PTY_TYPE=termios
   # since that just controls which of pty_XXXX.c file is use and
   # pty_termios.c is set up to handle pty_termio.
-  AC_MSG_CHECKING([for struct termio])
-  AC_TRY_RUN([#include <termio.h>
-  main()
-  {
-    struct termio tmp;
-    exit(0);
-  }],
+  AC_CHECK_TYPE([struct termio],[
         AC_DEFINE(HAVE_TERMIO)
         PTY_TYPE=termios
-        AC_MSG_RESULT(yes)
-,
-        AC_MSG_RESULT(no)
-,
-	AC_MSG_ERROR([Expect can't be cross compiled])
-)
+],[],[
+#include <termio.h>
+])
 
   # now check for the new style ttys (not yet posix)
-  AC_MSG_CHECKING([for struct termios])
-  AC_TRY_RUN([
+  AC_CHECK_TYPE([struct termios],[
+        AC_DEFINE(HAVE_TERMIOS)
+        PTY_TYPE=termios
+  ],[],[
   /* including termios.h on Solaris 5.6 fails unless inttypes.h included */
 #  ifdef HAVE_INTTYPES_H
 #  include <inttypes.h>
 #  endif
 #  include <termios.h>
-  main()
-  {
-    struct termios tmp;
-    exit(0);
-  }],
-        AC_DEFINE(HAVE_TERMIOS)
-        PTY_TYPE=termios
-        AC_MSG_RESULT(yes)
-  ,
-        AC_MSG_RESULT(no)
-  ,
-	AC_MSG_ERROR([Expect can't be cross compiled])
-  )
+  ])
 fi
 
 AC_MSG_CHECKING([if TCGETS or TCGETA in termios.h])
-AC_TRY_RUN([
+AC_TRY_COMPILE([
 /* including termios.h on Solaris 5.6 fails unless inttypes.h included */
 #ifdef HAVE_INTTYPES_H
 #include <inttypes.h>
 #endif
 #include <termios.h>
-main() {
+],[
 #if defined(TCGETS) || defined(TCGETA)
-	return 0;
 #else
-	return 1;
+#error missing
 #endif
-}],
+],[
 	AC_DEFINE(HAVE_TCGETS_OR_TCGETA_IN_TERMIOS_H)
 	AC_MSG_RESULT(yes)
-,
+],[
 	AC_MSG_RESULT(no)
-,
-	AC_MSG_ERROR([Expect can't be cross compiled])
-)
+])
 
 AC_MSG_CHECKING([if TIOCGWINSZ in termios.h])
-AC_TRY_RUN([
+AC_TRY_COMPILE([
 /* including termios.h on Solaris 5.6 fails unless inttypes.h included */
 #ifdef HAVE_INTTYPES_H
 #include <inttypes.h>
 #endif
 #include <termios.h>
-main() {
-#ifdef TIOCGWINSZ
-	return 0;
-#else
-	return 1;
+],[
+#ifndef TIOCGWINSZ
+#error missing
 #endif
-}],
+],[
 	AC_DEFINE(HAVE_TIOCGWINSZ_IN_TERMIOS_H)
 	AC_MSG_RESULT(yes)
-,
+],[
 	AC_MSG_RESULT(no)
-,
-	AC_MSG_ERROR([Expect can't be cross compiled])
-)
+])
 
 # finally check for Cray style ttys
 AC_MSG_CHECKING([for Cray-style ptys])
 SETUID=":"
-AC_TRY_RUN([
-main(){
-#ifdef CRAY
-	return 0;
-#else
-	return 1;
+AC_TRY_COMPILE([],[
+#ifndef CRAY
+#error missing
 #endif
-}
-],
+],[
 	PTY_TYPE=unicos
 	SETUID="chmod u+s"
 	AC_MSG_RESULT(yes)
-,
+],[
 	AC_MSG_RESULT(no)
-,
-	AC_MSG_ERROR([Expect can't be cross compiled])
-)
+])
 
 #
 # Check for select and/or poll. If both exist, we prefer select.
@@ -875,21 +818,16 @@
 # check for timezones
 #
 AC_MSG_CHECKING([for SV-style timezone])
-AC_TRY_RUN([
+AC_TRY_COMPILE([
 extern char *tzname[2];
 extern int daylight;
-main()
-{
+],[
   int *x = &daylight;
   char **y = tzname;
-
-  exit(0);
-}],
+],
 	AC_DEFINE(HAVE_SV_TIMEZONE)
 	AC_MSG_RESULT(yes),
 	AC_MSG_RESULT(no)
-,
-	AC_MSG_ERROR([Expect can't be cross compiled])
 )