Many autoconf tests for availability of some function involve trying
to link the same C code with different libraries in attempt to detect
which one contains the function. Typically C input is the same, and
even the intermediate object file being linked with libs is the same.
However, TRY_LINK always puts `conftest.c' on compiler command line,
so we obtain the same object code several times, each time going
through extremely time- consuming compilation phases. Why can not we
avoid this?
The following patch to 2.13 adds macros to perform recompilation
avoidance. They might be used like this (recompilations in
AC_CHECK_LIB remain)
AC_CHECK_HEADER(dlfcn.h, [
AC_CHECK_LIB(dl, dlopen, [ have_dl=yes libdl=dl], [
AC_CHECK_LIB(c, dlopen, [ have_dl=yes ], [
AC_MSG_CHECKING([for dlopen in -lc including <dlfcn.h>])
AC_TRY_COMPILE_NRM([#include <dlfcn.h>],dnl
[(void) dlopen ("", 0);], [
AC_TRY_LINK_O([ have_dl=yes ], [
AC_MSG_CHECKING([for dlopen in -ldl including <dlfcn.h>])
ac_save_LIBS="$LIBS"
LIBS="-ldl $LIBS"
AC_TRY_LINK_O([ have_dl=yes ], [LIBS="$ac_save_LIBS"])
ac_save_LIBS=])])])])])
--- acgeneral.m4 2000/12/22 15:20:58 1.1
+++ acgeneral.m4 2000/12/22 17:34:50 1.3
@@ -1254,6 +1254,15 @@
cross_compiling=$ac_cv_prog_f77_cross
])
+dnl AC_LANG_O()
+AC_DEFUN(AC_LANG_O,
+[define([AC_LANG], [O])dnl
+ac_ext=o
+ac_compile=:
+ac_link='${CC-cc} -o conftest${ac_exeext} $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext
+$LIBS 1>&AC_FD_CC'
+cross_compiling=$ac_cv_prog_cc_cross
+])
+
dnl Push the current language on a stack.
dnl AC_LANG_SAVE()
define(AC_LANG_SAVE,
@@ -1264,7 +1273,8 @@
pushdef([AC_LANG_RESTORE],
[ifelse(AC_LANG_STACK, [C], [AC_LANG_C],dnl
AC_LANG_STACK, [CPLUSPLUS], [AC_LANG_CPLUSPLUS],dnl
-AC_LANG_STACK, [FORTRAN77], [AC_LANG_FORTRAN77])[]popdef([AC_LANG_STACK])])
+AC_LANG_STACK, [FORTRAN77], [AC_LANG_FORTRAN77],dnl
+AC_LANG_STACK, [O], [AC_LANG_O])[]popdef([AC_LANG_STACK])])
dnl ### Compiler-running mechanics
@@ -1748,6 +1758,33 @@
])dnl
fi
rm -f conftest*])
+dnl AC_TRY_COMPILE_NRM(INCLUDES, FUNCTION-BODY,
+dnl [ACTION-IF-FOUND [, ACTION-IF-NOT-FOUND]])
+AC_DEFUN(AC_TRY_COMPILE_NRM,
+[cat > conftest.$ac_ext <<EOF
+ifelse(AC_LANG, [FORTRAN77],
+[ program main
+[$2]
+ end],
+[dnl This sometimes fails to find confdefs.h, for some reason.
+dnl [#]line __oline__ "[$]0"
+[#]line __oline__ "configure"
+#include "confdefs.h"
+[$1]
+int main() {
+[$2]
+; return 0; }
+])EOF
+if AC_TRY_EVAL(ac_compile); then
+ ifelse([$3], , :, [$3])
+else
+ echo "configure: failed program was:" >&AC_FD_CC
+ cat conftest.$ac_ext >&AC_FD_CC
+ifelse([$4], , , [ rm -rf conftest*
+ $4
+])dnl
+fi
+rm -f conftest*])
dnl ### Examining libraries
@@ -1792,6 +1829,26 @@
])dnl
fi
rm -f conftest*])
+dnl AC_TRY_LINK_O([ACTION-IF-FOUND [, ACTION-IF-NOT-FOUND]])
+AC_DEFUN(AC_TRY_LINK_O,
+[AC_LANG_SAVE()dnl
+AC_LANG_O
+if
+ AC_TRY_EVAL(ac_link)
+ ac_exit_status=$?
+ AC_LANG_RESTORE
+ test $ac_exit_status -eq 0 -a -s conftest${ac_exeext}
+then
+ ifelse([$1], , :, [rm -rf conftest${ac_exeext}
+ $1])
+else
+ echo "configure: failed program was:" >&AC_FD_CC
+ cat conftest.$ac_ext >&AC_FD_CC
+ifelse([$2], , , [ rm -rf conftest${ac_exeext}
+ $2
+])dnl
+fi
+rm -f conftest${ac_exeext}])
dnl ### Checking for run-time features
