https://github.com/fract4d/gnofract4d/pull/254

From dd92a4bf2c6e68352203c511f465846e5c96407b Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Fri, 14 Apr 2023 09:33:28 +0200
Subject: [PATCH] Declare image_lookup, gradient in fract_stdlib.h
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This avoids test failures in generated code with C compilers
that do not support implicit function declartions:

>           raise fracttypes.TranslationError(
                "Error reported by C compiler:%s" % output)
E           fract4d_compiler.fracttypes.TranslationError: Error reported by C co
mpiler:/tmp/fract4d_4tueiy9c/gnofract4d-cache/fract4d_9ebc1853081db2ea5eb7cce846
42cd4e.c: In function ‘pf_calc’:
E           /tmp/fract4d_4tueiy9c/gnofract4d-cache/fract4d_9ebc1853081db2ea5eb7c
ce84642cd4e.c:282:1: error: implicit declaration of function ‘image_lookup’
E             282 | image_lookup(t__a_cf1image,z_re,z_im, &t__cf10, &t__cf11, &t
__cf12);
E                 | ^~~~~~~~~~~~


>           raise fracttypes.TranslationError(
                "Error reported by C compiler:%s" % output)
E           fract4d_compiler.fracttypes.TranslationError: Error reported by C compiler:/tmp/fract4d_4tueiy9c/gnofract4d-cache/fract4d_2ccc81a001cdf717973d45d4cbd12778.c: In function ‘pf_calc’:
E           /tmp/fract4d_4tueiy9c/gnofract4d-cache/fract4d_2ccc81a001cdf717973d45d4cbd12778.c:323:1: error: implicit declaration of function ‘gradient’
E             323 | gradient(t__a__gradient,t__cf09, &t__cf010, &t__cf011, &t__cf012);
E                 | ^~~~~~~~
--- a/fract4d/c/fract_stdlib.h
+++ b/fract4d/c/fract_stdlib.h
@@ -52,6 +52,9 @@ extern "C"
     double read_float_array_2D(void *array, int x, int y);
     int write_float_array_2D(void *array, int x, int y, double val);
 
+    void image_lookup(void *im, double x, double y, double *pr, double *pg, double *pb);
+    void gradient(void *grad_object, double index, double *r, double *g, double *b);
+
 #ifdef __cplusplus
 }
 #endif