[Mesa-dev] [PATCH] glsl: prevent qualifiers modification of predeclared variables

[asimiklit.work at gmail.com]

From: Andrii Simiklit <andrii.simiklit at globallogic.com>

GLSL 3.7 (Identifiers):
"However, as noted in the specification, there are some cases where
previously declared variables can be redeclared to change or add some
property, and predeclared "gl_" names are allowed to be redeclared in a
shader only for these specific purposes.  More generally, it is an error to
redeclare a variable, including those starting "gl_"."

This patch should fix piglit tests:
'clip-distance-redeclare-without-inout.frag'
'clip-distance-redeclare-without-inout.vert'
and leads to regression in clip-distance-out-values.shader_test
but probably a fix should be made in the test.

As far as I understood following mailing thread:
https://lists.freedesktop.org/archives/piglit/2013-October/007935.html
looks like we have accepted to remove an ability to change qualifiers
but have not done it yet. Unless I missed something)

Fixes: 8e6cb9fe51a2 "glsl: Refactor AST-to-HIR code handling variable
					 redeclarations"
Signed-off-by: Andrii Simiklit <andrii.simiklit at globallogic.com>
---
 src/compiler/glsl/ast_to_hir.cpp | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/compiler/glsl/ast_to_hir.cpp b/src/compiler/glsl/ast_to_hir.cpp
index 93e7c8ec33..e26ae6b92a 100644
--- a/src/compiler/glsl/ast_to_hir.cpp
+++ b/src/compiler/glsl/ast_to_hir.cpp
@@ -4240,10 +4240,15 @@ get_variable_being_redeclared(ir_variable **var_ptr, YYLTYPE loc,
     */
    if (earlier->type->is_unsized_array() && var->type->is_array()
        && (var->type->fields.array == earlier->type->fields.array)) {
-      /* FINISHME: This doesn't match the qualifiers on the two
-       * FINISHME: declarations.  It's not 100% clear whether this is
-       * FINISHME: required or not.
-       */
+
+      if ((strcmp("gl_ClipDistance", var->name) == 0) &&
+          earlier->data.mode != var->data.mode) {
+         _mesa_glsl_error(&loc, state,
+                          "redeclaration of '%s %s' with incorrect qualifiers '%s'.",
+                          mode_string(earlier),
+                          var->name,
+                          mode_string(var));
+      }
 
       const int size = var->type->array_size();
       check_builtin_array_max_size(var->name, size, loc, state);
-- 
2.17.1