glxewInit check for current X11 display rather than crashing

auto/src/glew_init_glx.c

@@ -14,9 +14,13 @@ GLboolean glxewGetExtension (const char* name)
 
 GLenum glxewInit ()
 {
+  Display* display;
   int major, minor;
   const GLubyte* extStart;
   const GLubyte* extEnd;
+  /* check for a display */
+  display = glXGetCurrentDisplay();
+  if (display == NULL) return GLEW_ERROR_NO_GLX_DISPLAY;
   /* initialize core GLX 1.2 */
   if (_glewInit_GLX_VERSION_1_2()) return GLEW_ERROR_GLX_VERSION_11_ONLY;
   /* initialize flags */
@@ -26,7 +30,7 @@ GLenum glxewInit ()
   GLXEW_VERSION_1_3 = GL_TRUE;
   GLXEW_VERSION_1_4 = GL_TRUE;
   /* query GLX version */
-  glXQueryVersion(glXGetCurrentDisplay(), &major, &minor);
+  glXQueryVersion(display, &major, &minor);
   if (major == 1 && minor <= 3)
   {
     switch (minor)
@@ -46,7 +50,7 @@ GLenum glxewInit ()
   /* query GLX extension string */
   extStart = 0;
   if (glXGetCurrentDisplay != NULL)
-    extStart = (const GLubyte*)glXGetClientString(glXGetCurrentDisplay(), GLX_EXTENSIONS);
+    extStart = (const GLubyte*)glXGetClientString(display, GLX_EXTENSIONS);
   if (extStart == 0)
     extStart = (const GLubyte *)"";
   extEnd = extStart + _glewStrLen(extStart);

auto/src/glew_tail.h

@@ -6,6 +6,7 @@
 #define GLEW_ERROR_NO_GL_VERSION 1  /* missing GL version */
 #define GLEW_ERROR_GL_VERSION_10_ONLY 2  /* Need at least OpenGL 1.1 */
 #define GLEW_ERROR_GLX_VERSION_11_ONLY 3  /* Need at least GLX 1.2 */
+#define GLEW_ERROR_NO_GLX_DISPLAY 4  /* Need GLX display for GLX support */
 
 /* string codes */
 #define GLEW_VERSION 1