Fix a crash in miniTempWebGL*Buffers optimization #22130
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library_webgl.js attempts to use a pool of temp float or int buffers for uniform uploads up to 288 elements, however it would only allocate 288 temp buffers, so 0 through 287 would be fine but 288 would crash (miniTempWebGLFloatBuffers[288] would be undefined). Fix for emscripten-core#21573
sbc100
reviewed
Jun 22, 2024
| $miniTempWebGLFloatBuffers__postset: `var miniTempWebGLFloatBuffersStorage = new Float32Array({{{ GL_POOL_TEMP_BUFFERS_SIZE }}}); | ||
| for (/**@suppress{duplicate}*/var i = 0; i < {{{ GL_POOL_TEMP_BUFFERS_SIZE }}}; ++i) { | ||
| // Create GL_POOL_TEMP_BUFFERS_SIZE+1 temporary buffers, for uploads of size 0 through GL_POOL_TEMP_BUFFERS_SIZE inclusive | ||
| for (/**@suppress{duplicate}*/var i = 0; i <= {{{ GL_POOL_TEMP_BUFFERS_SIZE }}}; ++i) { |
Collaborator
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I guess I was the one who broke this in #21573?
Could we instead update all the other places where GL_POOL_TEMP_BUFFERS_SIZE to use less than? e.g. all the places there we currently do if (count <= {{{ GL_POOL_TEMP_BUFFERS_SIZE }}})
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I considered this but decided it didn't make as much sense. Then the top end would be unused for vec2/vec3/vec4 - the maximum values that hit the optimization would be:
- 287 floats
- 143 vec2s (286 floats)
- 95 vec3s (285 floats)
- 71 vec4s (284 floats)
Also
miniTempWebGLFloatBuffersStorage = new Float32Array({{{ GL_POOL_TEMP_BUFFERS_SIZE }}});
would change to
miniTempWebGLFloatBuffersStorage = new Float32Array({{{ GL_POOL_TEMP_BUFFERS_SIZE }}} - 1);
sbc100
approved these changes
Jun 24, 2024
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library_webgl.js attempts to use a pool of temp float or int buffers for uniform uploads up to 288 elements, however it would only allocate 288 temp buffers, so 0 through 287 would be fine but 288 would crash (miniTempWebGLFloatBuffers[288] would be undefined).
Confirmed manually that any one of the six "Just at the optimization limit" calls would crash before, and with the fix does not.
Fix for the change in PR #21573