MapBufferBuilder: fix size_t→int32 partial-write in putString/putMapBuffer length encoding#56525
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meta-yaohway wants to merge 1 commit intofacebook:mainfrom
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MapBufferBuilder: fix size_t→int32 partial-write in putString/putMapBuffer length encoding#56525meta-yaohway wants to merge 1 commit intofacebook:mainfrom
meta-yaohway wants to merge 1 commit intofacebook:mainfrom
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…uffer length encoding Summary: The MapBuffer wire format encodes lengths and offsets as `int32_t` (`MapBuffer::getString` / `getMapBuffer` read them as `*reinterpret_cast<const int32_t*>(...)`). But in `putString` and `putMapBuffer`: ```cpp auto strSize = value.size(); // size_t — 8 bytes on 64-bit memcpy(dynamicData_.data() + offset, &strSize, INT_SIZE); // copies first 4 of 8 bytes ``` `auto` deduces `size_t` from `.size()`, and `memcpy(&size_t_var, ..., 4)` writes only the **first 4 bytes** of an 8-byte object: - **little-endian:** writes the low 4 bytes — silent truncation if size > UINT32_MAX - **big-endian:** writes the high 4 bytes — encodes **zero** for normal sizes, producing a corrupt buffer the reader then trusts `putMapBufferList` already had the correct pattern: `auto offset = static_cast<int32_t>(dynamicData_.size())`. This diff applies that same explicit `static_cast<int32_t>` to `putString` (`strSize`, `offset`) and `putMapBuffer` (`mapBufferSize`, `offset`) so the value being `memcpy`'d is exactly `INT_SIZE` bytes wide. Changelog: [Internal] Reviewed By: NickGerleman Differential Revision: D100376322
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This pull request was successfully merged by @meta-yaohway in b111c0e When will my fix make it into a release? | How to file a pick request? |
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Summary:
The MapBuffer wire format encodes lengths and offsets as
int32_t(MapBuffer::getString/getMapBufferread them as*reinterpret_cast<const int32_t*>(...)). But inputStringandputMapBuffer:autodeducessize_tfrom.size(), andmemcpy(&size_t_var, ..., 4)writes only the first 4 bytes of an 8-byte object:putMapBufferListalready had the correct pattern:auto offset = static_cast<int32_t>(dynamicData_.size()). This diff applies that same explicitstatic_cast<int32_t>toputString(strSize,offset) andputMapBuffer(mapBufferSize,offset) so the value beingmemcpy'd is exactlyINT_SIZEbytes wide.Changelog: [Internal]
Reviewed By: NickGerleman
Differential Revision: D100376322