util: check for frag/vertShader=0 before attaching

diff --git a/progs/util/shaderutil.c b/progs/util/shaderutil.c
index 745851395a735ddbacb1e9b5b6571ebbb7957984..2f1c4e38b3004b180d37a38cd4cc9b215ef8c05b 100644 (file)
--- a/progs/util/shaderutil.c
+++ b/progs/util/shaderutil.c
@@ -6,6 +6,7 @@
  */
 
 
+#include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <GL/glut.h>
@@ -106,8 +107,12 @@ LinkShaders(GLuint vertShader, GLuint fragShader)
 {
    GLuint program = glCreateProgram_func();
 
-   glAttachShader_func(program, fragShader);
-   glAttachShader_func(program, vertShader);
+   assert(vertShader || fragShader);
+
+   if (fragShader)
+      glAttachShader_func(program, fragShader);
+   if (vertShader)
+      glAttachShader_func(program, vertShader);
    glLinkProgram_func(program);
 
    /* check link */