Make 64 bit compilation on 32 bit compiler possible

This patch is to be able to build ust with `i686-unknown-pc-gnu-gcc -m64', that
is, 32-bit compiler, 64-bit multilib.

diff --git a/configure.ac b/configure.ac
index b0320b02453dc62eb4a89998ff8784d778aa6dc3..73e95bb8bacc55458cf01762840840f925f5e5be 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -64,12 +64,38 @@ AC_CHECK_LIB([urcu-bp], [synchronize_rcu], [], [AC_MSG_ERROR([Cannot find liburc
 
 AC_CHECK_HEADERS([kcompat.h], [], [AC_MSG_ERROR([Cannot find kcompat headers (kcompat.h). Use [CFLAGS]=-Idir to specify their location.])])
 
+# Check for various supplementary host information (beyond the
+# triplet) which might affect the library format choices.  E.g., we
+# can be building with `i686-unknown-linux-gnu-gcc -m64'
+
+case "${host}" in
+changequote(,)dnl
+  i[34567]86-*-linux*)
+changequote([,])dnl
+    AC_CACHE_CHECK([if building for x86-64], [ust_cv_i386_is_x86_64],
+                    [save_CPPFLAGS="$CPPFLAGS"
+                    CPPFLAGS="$CPPFLAGS $CFLAGS"
+                    AC_EGREP_CPP([got it], [
+#if __x86_64__
+got it
+#endif
+                 ], [ust_cv_i386_is_x86_64=yes],
+                    [ust_cv_i386_is_x86_64=no])
+                    CPPFLAGS="$save_CPPFLAGS"])
+    ;;
+esac
+
 AC_MSG_CHECKING([library format for the host system])
 case $host_cpu in
-       i386) LIBFORMAT="elf32-i386" ;;
-       i486) LIBFORMAT="elf32-i386" ;;
-       i586) LIBFORMAT="elf32-i386" ;;
-       i686) LIBFORMAT="elf32-i386" ;;
+changequote(,)dnl
+       i[3456]86)
+changequote([,])dnl
+         if test "$ust_cv_i386_is_x86_64" = yes ; then
+            LIBFORMAT="elf64-x86-64"
+         else
+            LIBFORMAT="elf32-i386"
+         fi
+         ;;
        x86_64) LIBFORMAT="elf64-x86-64" ;;
        ppc) LIBFORMAT="elf32-powerpc" ;;
        ppc64) LIBFORMAT="elf64-powerpc" ;;