fix: avoid statx syscall so zmx runs on pre-4.11 kernels (#186)#188
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zmx crashed with `error: Unexpected` on every invocation on a Synology
DiskStation (Linux 4.4.302). `error.Unexpected` is what Zig's std returns
for an unrecognized errno; here the errno is ENOSYS (38) from the `statx`
syscall, which only exists on Linux >= 4.11.
Two code paths issued statx via Zig std, which calls the raw statx syscall
directly and does not fall back like libc does:
- log.zig: LogSystem.init() called file.getEndPos() -> File.stat() -> statx.
This runs before command parsing, so it broke *every* subcommand, not
just attach.
- socket.zig: sessionExists() called Dir.statFile() -> statx.
Both now use fd/at-based stat instead:
- LogSystem.init() uses posix.fstat(file.handle).
- sessionExists() uses posix.fstatatZ() + S.ISSOCK().
Because zmx links musl, these resolve to SYS_fstat / SYS_fstatat (musl on
x86_64 skips statx entirely), which are available on 4.4. Verified by
disassembling the release binary: no reachable statx call remains on the
attach path (the only residual references are the DWARF stack-trace
unwinder and sendFile fast-paths, neither of which zmx exercises).
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zmx crashed with
error: Unexpectedon every invocation on a Synology DiskStation (Linux 4.4.302).error.Unexpectedis what Zig's std returns for an unrecognized errno; here the errno is ENOSYS (38) from thestatxsyscall, which only exists on Linux >= 4.11.Two code paths issued statx via Zig std, which calls the raw statx syscall directly and does not fall back like libc does:
Both now use fd/at-based stat instead:
Because zmx links musl, these resolve to SYS_fstat / SYS_fstatat (musl on x86_64 skips statx entirely), which are available on 4.4. Verified by disassembling the release binary: no reachable statx call remains on the attach path (the only residual references are the DWARF stack-trace unwinder and sendFile fast-paths, neither of which zmx exercises).
Fixes #186