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Windows: support of long paths - #495
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Files were opened with the ANSI API (CreateFileA, fopen, _access_s, _mkdir, FindFirstFileExA...), limited to MAX_PATH (260 characters) for the full path, so e.g. the reversibility data of a file in a directory of 200 characters could not be created. File names are now converted to the wide API, with the \\?\ prefix on the full path (from GetFullPathNameW, so relative paths, '/' and ".." are handled as before) if it is too long for the Win32 API, without the need of the LongPathsEnabled system setting. Short paths are used as before. This is used for reading and writing files, creating directories, listing directories and removing or renaming temporary files. FFmpeg 6.0 and later support long paths too (4.2 and 4.4 do not).
The x86 linker does not support EH continuation metadata (LNK1246 with /guard:ehcont), so it is enabled only for x64. File sizes from the directory listing are computed with uintmax_t, the shift of the 32-bit size_t by 32 was undefined behavior (C4293) in 32-bit builds.
A DPX file in a directory of 230 characters is encoded with the FFmpeg command displayed by rawcooked then decoded, its reversibility data and its decoded file have more than 260 characters (MAX_PATH on Windows). A sequence in a directory of more than 300 characters is encoded with --check then decoded in a new directory of more than 300 characters. The current directory stays shorter than MAX_PATH, else Git Bash does not start native programs. On Windows, FFmpeg needs to support long paths too (FFmpeg 6.0 and later).
Windows is checked by GitHub Actions (MSVC2026 build and all the tests of make check in Git Bash). The AppVeyor configuration built the removed MSVC2019 project and ran only a part of the tests (last update in 2020).
JeromeMartinez
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