Added new M4 helper macro

m4/mhd_check_link_run.m4

@@ -0,0 +1,67 @@
+# SYNOPSIS
+#
+#   MHD_CHECK_LINK_RUN(MESSAGE, CACHE_ID, COMMAND_IF_CROSS_COMPILING, INPUT,
+#                      [ACTION_IF_SUCCEED], [ACTION_IF_FAILED])
+#
+# DESCRIPTION
+#
+#   Improved version of AC_RUN_IFELSE macro.
+#   Unlike AC_RUN_IFELSE, this macro tries to link the code if cross-compiling.
+#   Action COMMAND_IF_CROSS_COMPILING is executed only if link is succeed,
+#   otherwise CACHE_ID variable set to "no". 
+#   COMMAND_IF_CROSS_COMPILING action must set CACHE_ID variable to "yes", "no",
+#   "assuming yes" or "assuming no".
+#   ACTION_IF_SUCCEED is executed if result is "yes" or "assuming yes".
+#   ACTION_IF_FAILED is execuded if result is "no" or "assuming no".
+#
+#   Example usage:
+#
+#     MHD_CHECK_LINK_RUN([for valid snprintf()], [mhd_cv_snprintf_valid],
+#                        AC_LANG_PROGRAM([AC_INCLUDES_DEFAULT],
+#                                        [if (4 != snprintf(NULL, 0, "test"))
+#                                           return 2;])],
+#                        [mhd_cv_snprintf_valid='assuming no'])
+#
+#
+# LICENSE
+#
+#   Copyright (c) 2022 Karlson2k (Evgeny Grin) <[email protected]>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 1
+
+AC_DEFUN([MHD_CHECK_LINK_RUN],[dnl
+m4_ifblank([$1],[m4_fatal([$0: The first macro argument ("MESSAGE") must not be empty])])dnl
+m4_ifblank([$2],[m4_fatal([$0: The second macro argument ("CACHE_ID") must not be empty])])dnl
+m4_ifblank([$3],[m4_fatal([$0: The third macro argument ("COMMAND_IF_CROSS_COMPILING") ]dnl
+[must not be empty])])dnl
+m4_ifblank([$4],[m4_fatal([$0: The fourth macro argument ("INPUT") must not be empty])])dnl
+m4_bmatch(_mhd_norm_expd([$2]),[\s],dnl
+[m4_fatal([$0: The second macro argument ("CACHE_ID") must not contain whitespaces])])dnl
+m4_bmatch(_mhd_norm_expd([$3]),[\<]m4_re_escape(_mhd_norm_expd([$2]))[\>],[],dnl
+[m4_fatal([$0: The third macro argument ("COMMAND_IF_CROSS_COMPILING") must assign ]dnl
+[a value to the cache variable ']_mhd_norm_expd([$2])['])])dnl
+m4_pushdef([cacheVar],_mhd_norm_expd([$2]))dnl
+AC_CACHE_CHECK([$1],[$2],
+[
+AC_LANG_CONFTEST([$4])
+AS_VAR_IF([cross_compiling],["yes"],
+[AC_LINK_IFELSE([],[
+$3
+],[cacheVar='no'])dnl AC_LINK_IFELSE
+],dnl
+[AC_RUN_IFELSE([],[cacheVar='yes'],[cacheVar='no'],[[# Dummy placeholder]])
+])
+rm -f conftest.$ac_ext
+])
+m4_ifnblank([$5],[
+AS_IF([test "x$cacheVar" = "xyes" || test "x$cacheVar" = "xassuming yes"],[$5])dnl AS_IF
+])dnl m4_ifnblank
+m4_ifnblank([$6],[
+AS_IF([test "x$cacheVar" = "xno" || test "x$cacheVar" = "xassuming no"],[$6])dnl AS_IF
+])dnl m4_ifnblank
+])dnl AC_DEFUN