From 2c6ad763afa63e3326eef043eb0b2a87854cce9f Mon Sep 17 00:00:00 2001
From: Nigel Stewart <nigels@users.sourceforge.net>
Date: Sun, 13 Nov 2016 12:08:32 +1000
Subject: [PATCH] glxewInit check for current X11 display rather than crashing

---
 auto/src/glew_init_glx.c | 8 ++++++--
 auto/src/glew_tail.h     | 1 +
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/auto/src/glew_init_glx.c b/auto/src/glew_init_glx.c
index 159e45d..8c4596e 100644
--- a/auto/src/glew_init_glx.c
+++ b/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);
diff --git a/auto/src/glew_tail.h b/auto/src/glew_tail.h
index ce7ff3c..09daade 100644
--- a/auto/src/glew_tail.h
+++ b/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