Current autoconf triggers the obsolete AC_HEADER_STDC checks, so force things before zlib.

configure

@@ -1513,6 +1513,39 @@ fi
 
 } # ac_fn_c_try_compile
 
+# ac_fn_c_check_header_compile LINENO HEADER VAR INCLUDES
+# -------------------------------------------------------
+# Tests whether HEADER exists and can be compiled using the include files in
+# INCLUDES, setting the cache variable VAR accordingly.
+ac_fn_c_check_header_compile ()
+{
+  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $2" >&5
+printf %s "checking for $2... " >&6; }
+if eval test \${$3+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+$4
+#include <$2>
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"
+then :
+  eval "$3=yes"
+else $as_nop
+  eval "$3=no"
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+fi
+eval ac_res=\$$3
+	       { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
+printf "%s\n" "$ac_res" >&6; }
+  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
+
+} # ac_fn_c_check_header_compile
+
 # ac_fn_c_try_link LINENO
 # -----------------------
 # Try to link conftest.$ac_ext, and return whether this succeeded.
@@ -1621,39 +1654,6 @@ printf "%s\n" "$ac_res" >&6; }
   eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
 
 } # ac_fn_c_check_func
-
-# ac_fn_c_check_header_compile LINENO HEADER VAR INCLUDES
-# -------------------------------------------------------
-# Tests whether HEADER exists and can be compiled using the include files in
-# INCLUDES, setting the cache variable VAR accordingly.
-ac_fn_c_check_header_compile ()
-{
-  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
-  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $2" >&5
-printf %s "checking for $2... " >&6; }
-if eval test \${$3+y}
-then :
-  printf %s "(cached) " >&6
-else $as_nop
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-$4
-#include <$2>
-_ACEOF
-if ac_fn_c_try_compile "$LINENO"
-then :
-  eval "$3=yes"
-else $as_nop
-  eval "$3=no"
-fi
-rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
-fi
-eval ac_res=\$$3
-	       { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
-printf "%s\n" "$ac_res" >&6; }
-  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
-
-} # ac_fn_c_check_header_compile
 ac_configure_args_raw=
 for ac_arg
 do
@@ -3940,6 +3940,43 @@ printf "%s\n" "using $INSTALL" >&6; }
 
 
 
+ac_header= ac_cache=
+for ac_item in $ac_header_c_list
+do
+  if test $ac_cache; then
+    ac_fn_c_check_header_compile "$LINENO" $ac_header ac_cv_header_$ac_cache "$ac_includes_default"
+    if eval test \"x\$ac_cv_header_$ac_cache\" = xyes; then
+      printf "%s\n" "#define $ac_item 1" >> confdefs.h
+    fi
+    ac_header= ac_cache=
+  elif test $ac_header; then
+    ac_cache=$ac_item
+  else
+    ac_header=$ac_item
+  fi
+done
+
+
+
+
+
+
+
+
+if test $ac_cv_header_stdlib_h = yes && test $ac_cv_header_string_h = yes
+then :
+
+printf "%s\n" "#define STDC_HEADERS 1" >>confdefs.h
+
+fi
+ac_fn_c_check_header_compile "$LINENO" "math.h" "ac_cv_header_math_h" "$ac_includes_default"
+if test "x$ac_cv_header_math_h" = xyes
+then :
+
+fi
+
+
+
 ac_fn_c_check_func "$LINENO" "timegm" "ac_cv_func_timegm"
 if test "x$ac_cv_func_timegm" = xyes
 then :
@@ -4110,35 +4147,6 @@ PKGCONFIG_REQUIRES="zlib"
 
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for zlib via pkg-config" >&5
 printf %s "checking for zlib via pkg-config... " >&6; }
-ac_header= ac_cache=
-for ac_item in $ac_header_c_list
-do
-  if test $ac_cache; then
-    ac_fn_c_check_header_compile "$LINENO" $ac_header ac_cv_header_$ac_cache "$ac_includes_default"
-    if eval test \"x\$ac_cv_header_$ac_cache\" = xyes; then
-      printf "%s\n" "#define $ac_item 1" >> confdefs.h
-    fi
-    ac_header= ac_cache=
-  elif test $ac_header; then
-    ac_cache=$ac_item
-  else
-    ac_header=$ac_item
-  fi
-done
-
-
-
-
-
-
-
-
-if test $ac_cv_header_stdlib_h = yes && test $ac_cv_header_string_h = yes
-then :
-
-printf "%s\n" "#define STDC_HEADERS 1" >>confdefs.h
-
-fi
 if $PKGCONFIG --exists zlib
 then :
 
@@ -4213,7 +4221,6 @@ fi
 
 fi
 
-
 # Check whether --enable-libpng was given.
 if test ${enable_libpng+y}
 then :

configure.ac

@@ -88,6 +88,10 @@ AC_SUBST([INSTALL])
 AC_MSG_RESULT([using $INSTALL])
 
 
+dnl Standard C stuff...
+AC_CHECK_HEADER([math.h])
+
+
 dnl Check for date/time functionality...
 AC_CHECK_FUNC([timegm], [
     AC_DEFINE([HAVE_TIMEGM], [1], [Do we have the timegm function?])
@@ -141,7 +145,6 @@ AS_IF([$PKGCONFIG --exists zlib], [
     PKGCONFIG_LIBS_PRIVATE="-lz $PKGCONFIG_LIBS_PRIVATE"
 ])
 
-
 dnl libpng...
 AC_ARG_ENABLE([libpng], AS_HELP_STRING([--enable-libpng], [use libpng for pdfioFileCreateImageObjFromFile, default=auto]))