mhd_check_func.m4: added check for function declaration

m4/mhd_check_func.m4

@@ -9,13 +9,15 @@
 #
 #   This macro checks for presence of specific function by including
 #   specified headers and compiling and linking CHECK_CODE.
-#   This check both declaration and presence in library.
+#   This checks both declaration and presence in library.
+#   If function is available then macro HAVE_function_name (the name
+#   of the function convetedd to all uppercase characters) is defined
+#   automatically.
 #   Unlike AC_CHECK_FUNCS macro, this macro do not produce false
 #   negative result if function is declared with specific calling
 #   conventions like __stdcall' or attribute like
-#   __attribute__((__dllimport__)) and linker failed to build test
-#   program if library contains function with calling conventions
-#   different from declared. 
+#   __attribute__((__dllimport__)) and linker failing to build test
+#   program due to the different calling conventions. 
 #   By using definition from provided headers, this macro ensures that
 #   correct calling convention is used for detection.
 #
@@ -26,13 +28,13 @@
 #                    [const void *ptr = memmem("aa", 2, "a", 1); (void)ptr;],
 #                    [var_use_memmem='yes'], [var_use_memmem='no'])
 #
-#   Defined cache variable used in check so if any test will not work
+#   The cache variable used in check so if any test will not work
 #   correctly on some platform, user may simply fix it by giving cache
 #   variable in configure parameters, for example:
 #
 #     ./configure mhd_cv_func_memmem_have=no
 #
-#   This simplify building from source on exotic platforms as patching
+#   This simplifies building from source on exotic platforms as patching
 #   of configure.ac is not required to change results of tests.
 #
 # LICENSE
@@ -44,47 +46,59 @@
 #   and this notice are preserved. This file is offered as-is, without any
 #   warranty.
 
-#serial 4
+#serial 5
 
 AC_DEFUN([MHD_CHECK_FUNC],[dnl
-  AC_PREREQ([2.64])dnl for AS_VAR_IF, m4_ifblank, m4_ifnblank
-  m4_ifblank(m4_translit([$1],[()],[  ]), [m4_fatal([First macro argument must not be empty])])dnl
-  m4_ifblank([$3], [m4_fatal([Third macro argument must not be empty])])dnl
-  m4_bmatch(m4_normalize([$1]), [\s],dnl
-            [m4_fatal([First macro argument must not contain whitespaces])])dnl
-  m4_if(m4_index([$3], m4_normalize(m4_translit([$1],[()],[  ]))), [-1], dnl
-        [m4_fatal([CHECK_CODE parameter (third macro argument) does not contain ']m4_normalize([$1])[' token])])dnl
-  AS_VAR_PUSHDEF([cv_Var], [mhd_cv_func_]m4_bpatsubst(_mhd_norm_expd(m4_translit([$1],[()],[  ])),[[^a-zA-Z0-9]],[_]))dnl
-  dnl
-  AC_CACHE_CHECK([for function $1], cv_Var,
-    [dnl
-      m4_ifnblank([$6],[dnl
-        mhd_check_func_SAVE_LIBS="$LIBS"
-        LIBS="$LIBS _mhd_norm_expd([$6])"
-      ])dnl
-      AC_LINK_IFELSE(
-        [AC_LANG_SOURCE([
+AC_PREREQ([2.64])dnl for AS_VAR_IF, m4_ifblank, m4_ifnblank
+m4_newline([[# Expansion of $0 macro starts here]])
+AC_LANG_ASSERT([C])dnl
+m4_ifblank(m4_translit([$1],[()],[  ]), [m4_fatal([First macro argument must not be empty])])dnl
+m4_ifblank([$3], [m4_fatal([Third macro argument must not be empty])])dnl
+m4_bmatch(m4_normalize([$1]), [\s],dnl
+          [m4_fatal([First macro argument must not contain whitespaces])])dnl
+m4_if(m4_index([$3], m4_normalize(m4_translit([$1],[()],[  ]))), [-1], dnl
+      [m4_fatal([CHECK_CODE parameter (third macro argument) does not contain ']m4_normalize([$1])[' token])])dnl
+AS_VAR_PUSHDEF([decl_cv_Var],[ac_cv_have_decl_]m4_bpatsubst(_mhd_norm_expd(m4_translit([$1],[()],[  ])),[[^a-zA-Z0-9]],[_]))dnl
+AS_VAR_PUSHDEF([cv_Var],[mhd_cv_func_]m4_bpatsubst(_mhd_norm_expd(m4_translit([$1],[()],[  ])),[[^a-zA-Z0-9]],[_]))dnl
+AS_VAR_SET_IF([cv_Var],[],[AC_CHECK_DECL(_mhd_norm_expd([$1]),[],[],[$2])])
+AC_CACHE_CHECK([for function $1], [cv_Var],dnl
+  [dnl
+    AS_VAR_IF([decl_cv_Var],["yes"],dnl
+      [dnl
+        m4_ifnblank([$6],[dnl
+          mhd_check_func_SAVE_LIBS="$LIBS"
+          LIBS="_mhd_norm_expd([$6]) $LIBS"
+        ])dnl
+        AC_LINK_IFELSE(
+          [AC_LANG_SOURCE([
 m4_default_nblank([$2],[AC_INCLUDES_DEFAULT])
 
-int main(void)
+[int main(void)
 {
 
-  $3
+  ]$3[
 
   return 0;
 }
-          ])
-        ],
-        [AS_VAR_SET([cv_Var],["yes"])], [AS_VAR_SET([cv_Var],["no"])] ) 
-      m4_ifnblank([$6],[dnl
-        LIBS="${mhd_check_func_SAVE_LIBS}"
-        AS_UNSET([mhd_check_func_SAVE_LIBS])
-      ])dnl
-    ])
-  AS_VAR_IF([cv_Var], ["yes"],
-            [AC_DEFINE([[HAVE_]]m4_bpatsubst(m4_toupper(_mhd_norm_expd(m4_translit([$1],[()],[  ]))),[[^A-Z0-9]],[_]),
-                       [1], [Define to 1 if you have the ']_mhd_norm_expd(m4_translit([$1],[()],[  ]))[' function.])
-            m4_n([$4])dnl
-            ], [$5])
-  AS_VAR_POPDEF([cv_Var])dnl
-])
+            ]])
+          ],
+          [AS_VAR_SET([cv_Var],["yes"])],
+          [AS_VAR_SET([cv_Var],["no"])]dnl
+        )
+        m4_ifnblank([$6],[dnl
+          LIBS="${mhd_check_func_SAVE_LIBS}"
+          AS_UNSET([mhd_check_func_SAVE_LIBS])
+        ])dnl
+      ],[AS_VAR_SET([cv_Var],["no"])]dnl
+    )dnl
+  ]dnl
+)
+AS_VAR_IF([cv_Var], ["yes"],
+          [AC_DEFINE([[HAVE_]]m4_bpatsubst(m4_toupper(_mhd_norm_expd(m4_translit([$1],[()],[  ]))),[[^A-Z0-9]],[_]),
+                     [1], [Define to 1 if you have the ']_mhd_norm_expd(m4_translit([$1],[()],[  ]))[' function.])
+          m4_n([$4])dnl
+          ],[$5])
+AS_VAR_POPDEF([cv_Var])dnl
+AS_VAR_POPDEF([decl_cv_Var])dnl
+m4_newline([[# Expansion of $0 macro ends here]])
+])dnl AC_DEFUN MHD_CHECK_FUNC