emscripten webgpu.h bindings: WGPU_WHOLE_SIZE global constant leads to linker errors

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Andre Weissflog

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Feb 5, 2020, 10:57:54 AM2/5/20
to Dawn Graphics
Hi, I just stumbled over a little problem when using the new webgpu.h bindings in emscripten (provided by the Dawn team, that's why I'm posting here):

There's a globally visible symbol defined in the webgpu.h header:

const uint64_t WGPU_WHOLE_SIZE = 0xffffffffffffffffULL; // UINT64_MAX

If the header is now included in different compilation units, this leads to a linker error because the linker sees the same symbols multiple times:

wasm-ld: error: duplicate symbol: WGPU_WHOLE_SIZE
>>> defined in wgpu/CMakeFiles/clear-wgpu.dir/clear-wgpu.c.obj
>>> defined in wgpu/libwgpu_entry.a(wgpu_entry.c.obj)

Putting a "static" in front fixes the problem, however:

(1) WGPU_WHOLE_SIZE doesn't seem to be used anywhere in the header, so I wonder if it is necessary at all

(2) IMHO a traditional "#define WGPU_WHOLE_SIZE (0xffffffffffffffffULL)" would be better (since C doesn't have "proper" constants anyway)

Cheers!
-Floh.

Corentin Wallez

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Feb 5, 2020, 11:29:01 AM2/5/20
to Andre Weissflog, Dawn Graphics
Thanks for the report, that's indeed a C++ism that shouldn't be in the C header. Put up fixes for Dawn and webgpu-headers.

WGPU_WHOLE_SIZE can be used in the WGPUBindGroupBinding::size field to signify that the whole buffer should be used.

Cheers,

Corentin

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