[jira] [Resolved] (AVRO-4360) [C++] Float and double binary codecs use native byte order on big-endian hosts

["Fokko Driesprong (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/AVRO-4360?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Fokko Driesprong resolved AVRO-4360.
------------------------------------
    Resolution: Fixed

> [C++] Float and double binary codecs use native byte order on big-endian hosts
> ------------------------------------------------------------------------------
>
>                 Key: AVRO-4360
>                 URL: https://issues.apache.org/jira/browse/AVRO-4360
>             Project: Apache Avro
>          Issue Type: Bug
>          Components: c++
>            Reporter: Manu Zhang
>            Priority: Major
>              Labels: big-endian, pull-request-available, s390x
>          Time Spent: 40m
>  Remaining Estimate: 0h
>
> Avro C++ binary float/double encoding and decoding copy native memory bytes directly, while the Avro binary format requires little-endian IEEE 754 bytes.
> On a big-endian host such as s390x:
> * Encoding float 1.0 produces 3f 80 00 00 instead of 00 00 80 3f.
> * Encoding double 1.0 produces 3f f0 00 00 00 00 00 00 instead of 00 00 00 00 00 00 f0 3f.
> * Decoding valid little-endian Avro bytes produces incorrect values.
> Affected methods:
> * lang/c++/impl/BinaryEncoder.cc: BinaryEncoder::encodeFloat and encodeDouble.
> * lang/c++/impl/BinaryDecoder.cc: BinaryDecoder::decodeFloat and decodeDouble.
> The defect is present on current main, commit 28cb08c15543c8c2dd8d186db2029bfe760940a5. An encode/decode round trip on a single big-endian host can conceal it because the two incorrect operations cancel each other out.
> Reproduction and validation:
> * Independent fixed wire-byte tests for float and double, covering positive and negative zero, 1.0, -2.5, subnormal and normal limits, largest finite values, infinities, and quiet NaN payloads.
> * Stream chunk sizes of 1, 3 and 16 bytes.
> * GCC 14 s390x cross-build under QEMU: the original codec fails 120 of 132 assertions; the corrected codec passes all 132. This is emulation rather than physical s390x hardware.
> * Complete CodecTests passes on native macOS and Linux ARM64: 852 test cases and 103,659 assertions on each.
> Expected behavior: encode and decode the required little-endian wire bytes while preserving raw IEEE 754 bits.
> Proposed fix uses C++20 bit_cast and endian-aware byte reversal in all four methods. Regression tests check each direction independently.
> Pull request: https://github.com/apache/avro/pull/4043
> Specification: https://avro.apache.org/docs/1.12.0/specification/



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