diff --git a/panda/src/glstuff/glGraphicsBuffer_src.cxx b/panda/src/glstuff/glGraphicsBuffer_src.cxx
index 05d8c4b78f..cd40b52384 100644
--- a/panda/src/glstuff/glGraphicsBuffer_src.cxx
+++ b/panda/src/glstuff/glGraphicsBuffer_src.cxx
@@ -1062,6 +1062,7 @@ attach_tex(int layer, int view, Texture *attach, GLenum attachpoint) {
 #ifndef OPENGLES
   if (_rb_size_z != 1) {
     // Bind all of the layers of the texture.
+    nassertv(glgsg->_glFramebufferTexture != NULL);
     glgsg->_glFramebufferTexture(GL_FRAMEBUFFER_EXT, attachpoint,
                                  gtc->_index, 0);
     return;
diff --git a/panda/src/glstuff/glGraphicsStateGuardian_src.cxx b/panda/src/glstuff/glGraphicsStateGuardian_src.cxx
index cb7b0e4da3..db342f423a 100644
--- a/panda/src/glstuff/glGraphicsStateGuardian_src.cxx
+++ b/panda/src/glstuff/glGraphicsStateGuardian_src.cxx
@@ -829,13 +829,22 @@ reset() {
 
   _supports_2d_texture_array = false;
 #ifndef OPENGLES
-  _supports_2d_texture_array = has_extension("GL_EXT_texture_array");
-  if (_supports_2d_texture_array) {
+  if (is_at_least_gl_version(3, 0)) {
+    _supports_2d_texture_array = true;
+
+    _glFramebufferTextureLayer = (PFNGLFRAMEBUFFERTEXTURELAYERPROC)
+      get_extension_func("glFramebufferTextureLayer");
+
+  } else if (has_extension("GL_EXT_texture_array")) {
+    _supports_2d_texture_array = true;
+
     _glFramebufferTextureLayer = (PFNGLFRAMEBUFFERTEXTURELAYERPROC)
       get_extension_func("glFramebufferTextureLayerEXT");
-  } else {
-    // ARB_geometry_shader4 also provides a version.
-    _glFramebufferTextureLayer = NULL;
+  }
+
+  if (_supports_2d_texture_array && _glFramebufferTextureLayer == NULL) {
+    GLCAT.warning()
+      << "Texture arrays advertised as supported by OpenGL runtime, but could not get pointer to glFramebufferTextureLayer function.\n";
   }
 #endif
 
@@ -1263,20 +1272,40 @@ reset() {
 #endif // HAVE_CG
 
 
-#ifdef OPENGLES_2
+#if defined(OPENGLES_1)
+  _supports_glsl = false;
+  _supports_geometry_shaders = false;
+  _supports_tessellation_shaders = false;
+#elif defined(OPENGLES)
   _supports_glsl = true;
   _supports_geometry_shaders = false;
   _supports_tessellation_shaders = false;
 #else
-  #ifdef OPENGLES_1
-    _supports_glsl = false;
+  _supports_glsl = is_at_least_gl_version(2, 0) || has_extension("GL_ARB_shading_language_100");
+  _supports_tessellation_shaders = is_at_least_gl_version(4, 0) || has_extension("GL_ARB_tessellation_shader");
+
+  if (is_at_least_gl_version(3, 2)) {
+    _supports_geometry_shaders = true;
+    _glFramebufferTexture = (PFNGLFRAMEBUFFERTEXTUREARBPROC)
+      get_extension_func("glFramebufferTexture");
+
+  } else if (has_extension("GL_ARB_geometry_shader4")) {
+    _supports_geometry_shaders = true;
+    _glFramebufferTexture = (PFNGLFRAMEBUFFERTEXTUREARBPROC)
+      get_extension_func("glFramebufferTextureARB");
+    _glProgramParameteri = (PFNGLPROGRAMPARAMETERIPROC)
+      get_extension_func("glProgramParameteriARB");
+
+  } else if (has_extension("GL_EXT_geometry_shader4")) {
+    _supports_geometry_shaders = true;
+    _glFramebufferTexture = NULL;
+    _glProgramParameteri = (PFNGLPROGRAMPARAMETERIPROC)
+      get_extension_func("glProgramParameteriEXT");
+
+  } else {
     _supports_geometry_shaders = false;
-    _supports_tessellation_shaders = false;
-  #else
-    _supports_glsl = is_at_least_gl_version(2, 0) || has_extension("GL_ARB_shading_language_100");
-    _supports_geometry_shaders = is_at_least_gl_version(3, 2) || has_extension("GL_ARB_geometry_shader4");
-    _supports_tessellation_shaders = is_at_least_gl_version(4, 0) || has_extension("GL_ARB_tessellation_shader");
-  #endif
+    _glFramebufferTexture = NULL;
+  }
 #endif
   _shader_caps._supports_glsl = _supports_glsl;
 
@@ -1378,17 +1407,6 @@ reset() {
       _glVertexAttribLPointer = NULL;
     }
 
-    if (_supports_geometry_shaders) {
-      _glProgramParameteri = (PFNGLPROGRAMPARAMETERIPROC)
-        get_extension_func("glProgramParameteri");
-      _glFramebufferTexture = (PFNGLFRAMEBUFFERTEXTUREARBPROC)
-        get_extension_func("glFramebufferTextureARB");
-
-      if (_glFramebufferTextureLayer == NULL) {
-        _glFramebufferTextureLayer = (PFNGLFRAMEBUFFERTEXTURELAYERPROC)
-          get_extension_func("glFramebufferTextureLayerARB");
-      }
-    }
     if (_supports_tessellation_shaders) {
       _glPatchParameteri = (PFNGLPATCHPARAMETERIPROC)
          get_extension_func("glPatchParameteri");
@@ -1533,7 +1551,7 @@ reset() {
     _glDrawElementsInstanced = (PFNGLDRAWELEMENTSINSTANCEDPROC)
       get_extension_func("glDrawElementsInstancedARB");
     _supports_geometry_instancing = true;
-  
+
   } else if (has_extension("GL_EXT_draw_instanced")) {
     _glDrawArraysInstanced = (PFNGLDRAWARRAYSINSTANCEDPROC)
       get_extension_func("glDrawArraysInstancedEXT");
@@ -2202,8 +2220,10 @@ reset() {
   if (is_at_least_gl_version(4, 1) || has_extension("GL_ARB_get_program_binary")) {
     _glGetProgramBinary = (PFNGLGETPROGRAMBINARYPROC)
       get_extension_func("glGetProgramBinary");
+    _glProgramParameteri = (PFNGLPROGRAMPARAMETERIPROC)
+      get_extension_func("glProgramParameteri");
 
-    if (_glGetProgramBinary != NULL) {
+    if (_glGetProgramBinary != NULL && _glProgramParameteri != NULL) {
       _supports_get_program_binary = true;
     }
   }
diff --git a/panda/src/glstuff/glShaderContext_src.cxx b/panda/src/glstuff/glShaderContext_src.cxx
index bb58a45572..2a67e0ba21 100644
--- a/panda/src/glstuff/glShaderContext_src.cxx
+++ b/panda/src/glstuff/glShaderContext_src.cxx
@@ -212,10 +212,11 @@ CLP(ShaderContext)(CLP(GraphicsStateGuardian) *glgsg, Shader *s) : ShaderContext
   if (_glsl_parameter_map.size() == 0) {
     int seqno = 0, texunitno = 0, imgunitno = 0;
     string noprefix;
-    GLint param_count, param_maxlength, param_size;
+    GLint param_count = 0, param_maxlength = 0, param_size;
     GLenum param_type;
     _glgsg->_glGetProgramiv(_glsl_program, GL_ACTIVE_UNIFORMS, &param_count);
     _glgsg->_glGetProgramiv(_glsl_program, GL_ACTIVE_UNIFORM_MAX_LENGTH, &param_maxlength);
+    param_maxlength = max(64, param_maxlength);
     char* param_name_cstr = (char *)alloca(param_maxlength);
 
     for (int i = 0; i < param_count; ++i) {
@@ -856,6 +857,7 @@ CLP(ShaderContext)(CLP(GraphicsStateGuardian) *glgsg, Shader *s) : ShaderContext
     // Now we've processed the uniforms, we'll process the attribs.
     _glgsg->_glGetProgramiv(_glsl_program, GL_ACTIVE_ATTRIBUTES, &param_count);
     _glgsg->_glGetProgramiv(_glsl_program, GL_ACTIVE_ATTRIBUTE_MAX_LENGTH, &param_maxlength);
+    param_maxlength = max(64, param_maxlength);
     param_name_cstr = (char *)alloca(param_maxlength);
 
     for (int i = 0; i < param_count; ++i) {
@@ -1940,13 +1942,13 @@ glsl_compile_and_link() {
   if (!_shader->get_text(Shader::ST_geometry).empty()) {
     valid &= glsl_compile_shader(Shader::ST_geometry);
 
-    // Set the vertex output limit to the maximum.
-    // This is slow, but it is probably reasonable to require
-    // the user to override this in his shader using layout().
-    nassertr(_glgsg->_glProgramParameteri != NULL, false);
-    GLint max_vertices;
-    glGetIntegerv(GL_MAX_GEOMETRY_OUTPUT_VERTICES, &max_vertices);
-    _glgsg->_glProgramParameteri(_glsl_program, GL_GEOMETRY_VERTICES_OUT_ARB, max_vertices);
+    //XXX Actually, it turns out that this is unavailable in the core
+    // version of geometry shaders.  Probably no need to bother with it.
+
+    //nassertr(_glgsg->_glProgramParameteri != NULL, false);
+    //GLint max_vertices;
+    //glGetIntegerv(GL_MAX_GEOMETRY_OUTPUT_VERTICES, &max_vertices);
+    //_glgsg->_glProgramParameteri(_glsl_program, GL_GEOMETRY_VERTICES_OUT_ARB, max_vertices);
   }
 #endif