sokol_gfx.h gl: fix max number of storage buffer bindings (fixes #1193) (#1196)

CHANGELOG.md

@@ -1,5 +1,30 @@
 ## Updates
 
+### 23-Jan-2025
+
+A minor, potentially breaking update in the sokol-gfx GL backend when
+using storage buffers on the fragment shader stage:
+
+The GL backend will no longer use storage buffer bindslots in the
+range 8..15. This allows sokol-gfx to be used on GL drivers
+that only support the minimal number of storage buffer bindings.
+
+This may be a breaking change if you are using sokol-shdc with the glsl430
+output format which uses storage buffers on the fragment shader stage.
+
+Previously this would assign storage buffer bindings on the fragment stage
+to the bind slot range 8..15 which will now cause a validation layer error
+in debug mode, or a panic-level error in release mode (which won't have a lot
+of information in release mode, rebuild in debug to get much more useful
+error messages).
+
+To fix this problem, just recompile your shaders with the latest sokol-shdc.
+
+Also see issue https://github.com/floooh/sokol/issues/1193 and the PRs
+https://github.com/floooh/sokol/pull/1196 and https://github.com/floooh/sokol-tools/pull/170
+for details.
+
+
 ### 12-Jan-2025
 
 - The Jai and D language bindings now also have integrated comments

sokol_gfx.h

@@ -776,7 +776,7 @@
               (in HLSL, storage buffers and texture share the same bind space)
             - Metal/MSL: the buffer bind slot N (`[[buffer(N)]]`) where N is 8..15
             - WebGPU/WGSL: the binding N in `@group(0) @binding(N)` where N is 0..127
-            - GL/GLSL: the buffer binding N in `layout(binding=N)` where N is 0..16
+            - GL/GLSL: the buffer binding N in `layout(binding=N)` where N is 0..7
         - note that storage buffers are not supported on all backends
           and platforms
 
@@ -3062,7 +3062,7 @@ typedef struct sg_sampler_desc {
             - HLSL: the texture(sic) register `register(t0..23)`
             - MSL: the buffer attribute `[[buffer(8..15)]]`
             - WGSL: the binding in `@group(1) @binding(0..127)`
-            - GL: the binding in `layout(binding=0..16)`
+            - GL: the binding in `layout(binding=0..7)`
 
     - reflection information for each combined image-sampler object
       used by the shader:
@@ -3683,6 +3683,7 @@ typedef struct sg_frame_stats {
     _SG_LOGITEM_XMACRO(GL_TEXTURE_FORMAT_NOT_SUPPORTED, "pixel format not supported for texture (gl)") \
     _SG_LOGITEM_XMACRO(GL_3D_TEXTURES_NOT_SUPPORTED, "3d textures not supported (gl)") \
     _SG_LOGITEM_XMACRO(GL_ARRAY_TEXTURES_NOT_SUPPORTED, "array textures not supported (gl)") \
+    _SG_LOGITEM_XMACRO(GL_STORAGEBUFFER_GLSL_BINDING_OUT_OF_RANGE, "GLSL storage buffer bindslot is out of range (must be 0..7) (gl)") \
     _SG_LOGITEM_XMACRO(GL_SHADER_COMPILATION_FAILED, "shader compilation failed (gl)") \
     _SG_LOGITEM_XMACRO(GL_SHADER_LINKING_FAILED, "shader linking failed (gl)") \
     _SG_LOGITEM_XMACRO(GL_VERTEX_ATTRIBUTE_NOT_FOUND_IN_SHADER, "vertex attribute not found in shader; NOTE: may be caused by GL driver's GLSL compiler removing unused globals") \
@@ -3828,7 +3829,7 @@ typedef struct sg_frame_stats {
     _SG_LOGITEM_XMACRO(VALIDATE_SHADERDESC_STORAGEBUFFER_METAL_BUFFER_SLOT_COLLISION, "storage buffer 'msl_buffer_n' must be unique across uniform blocks and storage buffer in same shader stage") \
     _SG_LOGITEM_XMACRO(VALIDATE_SHADERDESC_STORAGEBUFFER_HLSL_REGISTER_T_OUT_OF_RANGE, "storage buffer 'hlsl_register_t_n' is out of range (must be 0..23)") \
     _SG_LOGITEM_XMACRO(VALIDATE_SHADERDESC_STORAGEBUFFER_HLSL_REGISTER_T_COLLISION, "storage_buffer 'hlsl_register_t_n' must be unique across storage buffers and images in same shader stage") \
-    _SG_LOGITEM_XMACRO(VALIDATE_SHADERDESC_STORAGEBUFFER_GLSL_BINDING_OUT_OF_RANGE, "storage buffer 'glsl_binding_n' is out of range (must be 0..15)") \
+    _SG_LOGITEM_XMACRO(VALIDATE_SHADERDESC_STORAGEBUFFER_GLSL_BINDING_OUT_OF_RANGE, "storage buffer 'glsl_binding_n' is out of range (must be 0..7)") \
     _SG_LOGITEM_XMACRO(VALIDATE_SHADERDESC_STORAGEBUFFER_GLSL_BINDING_COLLISION, "storage buffer 'glsl_binding_n' must be unique across shader stages") \
     _SG_LOGITEM_XMACRO(VALIDATE_SHADERDESC_STORAGEBUFFER_WGSL_GROUP1_BINDING_OUT_OF_RANGE, "storage buffer 'wgsl_group1_binding_n' is out of range (must be 0..127)") \
     _SG_LOGITEM_XMACRO(VALIDATE_SHADERDESC_STORAGEBUFFER_WGSL_GROUP1_BINDING_COLLISION, "storage buffer 'wgsl_group1_binding_n' must be unique across all images, samplers and storage buffers") \
@@ -5566,7 +5567,7 @@ typedef struct {
     GLuint sampler;
 } _sg_gl_cache_texture_sampler_bind_slot;
 
-#define _SG_GL_MAX_SBUF_BINDINGS (2 * SG_MAX_STORAGEBUFFER_BINDSLOTS)
+#define _SG_GL_MAX_SBUF_BINDINGS (SG_MAX_STORAGEBUFFER_BINDSLOTS)
 #define _SG_GL_MAX_IMG_SMP_BINDINGS (SG_MAX_IMAGE_SAMPLER_PAIRS)
 typedef struct {
     sg_depth_state depth;
@@ -8704,11 +8705,25 @@ _SOKOL_PRIVATE GLuint _sg_gl_compile_shader(sg_shader_stage stage, const char* s
     return gl_shd;
 }
 
+// NOTE: this is an out-of-range check for GLSL bindslots that's also active in release mode
+_SOKOL_PRIVATE void _sg_gl_ensure_glsl_bindslot_ranges(const sg_shader_desc* desc) {
+    SOKOL_ASSERT(desc);
+    for (size_t i = 0; i < SG_MAX_STORAGEBUFFER_BINDSLOTS; i++) {
+        if (desc->storage_buffers[i].glsl_binding_n >= _SG_GL_MAX_SBUF_BINDINGS) {
+            _SG_PANIC(GL_STORAGEBUFFER_GLSL_BINDING_OUT_OF_RANGE);
+        }
+    }
+}
+
 _SOKOL_PRIVATE sg_resource_state _sg_gl_create_shader(_sg_shader_t* shd, const sg_shader_desc* desc) {
     SOKOL_ASSERT(shd && desc);
     SOKOL_ASSERT(!shd->gl.prog);
     _SG_GL_CHECK_ERROR();
 
+    // perform a fatal range-check on GLSL bindslots that's also active
+    // in release mode to avoid potential out-of-bounds array accesses
+    _sg_gl_ensure_glsl_bindslot_ranges(desc);
+
     // copy the optional vertex attribute names over
     for (int i = 0; i < SG_MAX_VERTEX_ATTRIBUTES; i++) {
         _sg_strcpy(&shd->gl.attrs[i].name, desc->attrs[i].glsl_name);