[mypyc] Move API tables to static_data.c#21183
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p-sawicki wants to merge 2 commits intopython:masterfrom
Open
[mypyc] Move API tables to static_data.c#21183p-sawicki wants to merge 2 commits intopython:masterfrom
p-sawicki wants to merge 2 commits intopython:masterfrom
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JukkaL
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Apr 8, 2026
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| #ifdef MYPYC_EXPERIMENTAL | ||
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| void *LibRTStrings_API[LIBRT_STRINGS_API_LEN] = {0}; |
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Now all the API tables will always be included in each build, which increases the memory usage of each module a little. It's not a big deal right now, but this is not scalable if we add many librt submodules in the future. Could we instead have librt_vecs_static.c etc. and add them as dependencies?
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lib-rt API tables are defined as static variables in lib-rt headers. This means that each translation unit gets its own independent instance of these variables.
That becomes a problem in multi-file compilation mode when using
BytesWriter.write, as this function is translated toCPyBytesWriter_Writeby mypyc which is defined inbytes_writer_extra_ops.c. With multi-file compilation,bytes_writer_extra_ops.cis compiled as its own translation unit and gets linked with the C extension compiled from python files.The C extension TU copies the
librt.stringscapsule contents into the global table but because it's static this is not visible in the table in thebytes_writer_extra_ops.cTU, which stays zero-initialized. This results in a seg fault with the following call chain:CPyBytesWriter_Write->CPyBytesWriter_EnsureSize->LibRTStrings_ByteWriter_grow_buffer_internal->LibRTStrings_API[5]-> oops all zerosTo fix this, declare the tables as
externand define them instatic_data.cso there's only one global version of each variable.