[Mesa-dev] [PATCH] glsl: handle unsigned int wraparound in link_shaders()

[Lars Hamre]

check_explicit_uniform_locations() returns a -1 when the extension
ARB_explicit_uniform_location is not found.

We were storing the result in num_explicit_uniform_locs as an
unsigned int which caused it to be 4294967295 when a -1 was returned.

This in turn would cause the following error during linking:
error: count of uniform locations > MAX_UNIFORM_LOCATIONS(4294967295 > 98304)

Here are the results from running piglit tests/all with this patch:
changes:     178
fixes:       176
regressions: 2

The two regressions are for the following tests:
glean at glsl1-matrix column check (1)
glean at glsl1-matrix column check (2)
which regress from FAIL to CRASH.

I am okay with these regressions because the tests are currently
failing due to the aforementioned linker error.

Signed-off-by: Lars Hamre <chemecse at gmail.com>

---
 src/compiler/glsl/linker.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
index cd35464..a0a9104 100644
--- a/src/compiler/glsl/linker.cpp
+++ b/src/compiler/glsl/linker.cpp
@@ -4171,7 +4171,7 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)

    tfeedback_decl *tfeedback_decls = NULL;
    unsigned num_tfeedback_decls = prog->TransformFeedback.NumVarying;
-   unsigned int num_explicit_uniform_locs = 0;
+   int num_explicit_uniform_locs = 0;

    void *mem_ctx = ralloc_context(NULL); // temporary linker context

@@ -4354,6 +4354,8 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
    }

    num_explicit_uniform_locs = check_explicit_uniform_locations(ctx, prog);
+   if (num_explicit_uniform_locs < 0)
+      num_explicit_uniform_locs = 0;
    link_assign_subroutine_types(prog);

    if (!prog->LinkStatus)
@@ -4585,7 +4587,7 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)

    update_array_sizes(prog);
    link_assign_uniform_locations(prog, ctx->Const.UniformBooleanTrue,
-                                 num_explicit_uniform_locs,
+                                 (unsigned int)num_explicit_uniform_locs,
                                  ctx->Const.MaxUserAssignableUniformLocations);
    link_assign_atomic_counter_resources(ctx, prog);
    store_fragdepth_layout(prog);
--
2.5.5