new file mode 100644
--- /dev/null
+++ b/m4/decl.m4
@@ -0,0 +1,54 @@
+AC_DEFUN(jm_CHECK_DECLARATION,
+[
+test -z "$ac_cv_header_strings_h" && AC_CHECK_HEADERS(strings.h)
+test -z "$ac_cv_header_stdlib_h" && AC_CHECK_HEADERS(stdlib.h)
+test -z "$ac_cv_header_unistd_h" && AC_CHECK_HEADERS(unistd.h)
+AC_MSG_CHECKING([whether $1 is declared])
+AC_CACHE_VAL(jm_cv_func_decl_$1,
+[AC_TRY_COMPILE([
+#include <stdio.h>
+#ifdef HAVE_STRING_H
+# include <string.h>
+#else
+# ifdef HAVE_STRINGS_H
+#  include <strings.h>
+# endif
+#endif
+#ifdef HAVE_STDLIB_H
+# include <stdlib.h>
+#endif
+#ifdef HAVE_UNISTD_H
+# include <unistd.h>
+#endif],
+[
+#ifndef $1
+char *(*pfn) = (char *(*)) $1
+#endif
+],
+  eval "jm_cv_func_decl_$1=yes",
+  eval "jm_cv_func_decl_$1=no")])
+
+if eval "test \"`echo '$jm_cv_func_decl_'$1`\" = yes"; then
+  AC_MSG_RESULT(yes)
+  ifelse([$2], , :, [$2])
+else
+  AC_MSG_RESULT(no)
+  ifelse([$3], , , [$3
+])dnl
+fi
+])dnl
+
+dnl jm_CHECK_DECLARATIONS(FUNCTION... [, ACTION-IF-DECLARED
+dnl                       [, ACTION-IF-NOT-DECLARED]])
+AC_DEFUN(jm_CHECK_DECLARATIONS,
+[
+  for jm_func in $1
+  do
+    jm_CHECK_DECLARATION($jm_func,
+    [
+      lower=abcdefghijklmnopqrstuvwxyz
+      upper=ABCDEFGHIJKLMNOPQRSTUVWXYZ
+      jm_tr_func=HAVE_DECLARATION_`echo $jm_func | tr $lower $upper`
+      AC_DEFINE_UNQUOTED($jm_tr_func) $2], $3)dnl
+  done
+])

new file mode 100644
--- /dev/null
+++ b/m4/do-decl.m4
@@ -0,0 +1,14 @@
+dnl This is just a wrapper function to encapsulate this kludge.
+dnl Putting it in a separate file like this helps share it between
+dnl different packages.
+AC_DEFUN(jm_CHECK_DECLS,
+[
+  if test x = y; then
+    dnl This code is deliberately never run via ./configure.
+    dnl FIXME: this is a gross hack to make autoheader put entries
+    dnl for each of these symbols in the config.h.in.
+    AC_CHECK_FUNCS(DECLARATION_FREE DECLARATION_MALLOC DECLARATION_REALLOC \
+		   DECLARATION_STPCPY DECLARATION_STRSTR)
+  fi
+  jm_CHECK_DECLARATIONS(free malloc realloc stpcpy strstr)
+])