+ * Append string 'b' onto string 'a'. Free 'a' and return new string.
+ */
+static char *
+append(const char *a, const char *b)
+{
+ const GLuint aLen = a ? _mesa_strlen(a) : 0;
+ const GLuint bLen = b ? _mesa_strlen(b) : 0;
+ char *s = _mesa_calloc(aLen + bLen + 1);
+ if (s) {
+ if (a)
+ _mesa_memcpy(s, a, aLen);
+ if (b)
+ _mesa_memcpy(s + aLen, b, bLen);
+ s[aLen + bLen] = '\0';
+ }
+ if (a)
+ _mesa_free((void *) a);
+ return s;
+}
+
+
+/**
+ * Check the MESA_EXTENSION_OVERRIDE env var.
+ * For extension names that are recognized, turn them on. For extension
+ * names that are recognized and prefixed with '-', turn them off.
+ * Return a string of the unknown/leftover names.
+ */
+static const char *
+get_extension_override( GLcontext *ctx )
+{
+ const char *envExt = _mesa_getenv("MESA_EXTENSION_OVERRIDE");
+ char *extraExt = NULL;
+ char ext[1000];
+ GLuint extLen = 0;
+ GLuint i;
+ GLboolean disableExt = GL_FALSE;
+
+ if (!envExt)
+ return NULL;
+
+ for (i = 0; ; i++) {
+ if (envExt[i] == '\0' || envExt[i] == ' ') {
+ /* terminate/process 'ext' if extLen > 0 */
+ if (extLen > 0) {
+ assert(extLen < sizeof(ext));
+ /* enable extension named by 'ext' */
+ ext[extLen] = 0;
+ if (!set_extension(ctx, ext, !disableExt)) {
+ /* unknown extension name, append it to extraExt */
+ if (extraExt) {
+ extraExt = append(extraExt, " ");
+ }
+ extraExt = append(extraExt, ext);
+ }
+ extLen = 0;
+ disableExt = GL_FALSE;
+ }
+ if (envExt[i] == '\0')
+ break;
+ }
+ else if (envExt[i] == '-') {
+ disableExt = GL_TRUE;
+ }
+ else {
+ /* accumulate this non-space character */
+ ext[extLen++] = envExt[i];
+ }
+ }
+
+ return extraExt;
+}
+
+
+/**