refactor(delib-1a): platform pfd I/O uses Linux direct syscalls#47
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refactor(delib-1a): platform pfd I/O uses Linux direct syscalls#47
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First step toward the W46 un-link-libc migration. Replace
`std.c.{write,read,pread,pwrite,lseek,close,fsync}` inside
`platform.pfd*` helpers with `std.os.linux.*` direct syscalls
on Linux. Mac/BSD keep `std.c.*` (libSystem auto-link, still works).
Windows keeps the Win32 path added in 1af72d1.
Behavior unchanged: callers that read `std.c._errno()` still see
the right errno because the Linux branch mirrors the syscall's
errno into `_errno().*` before returning -1. `link_libc = true`
still on — actually removing it needs the path-based ops
(mkdirat / unlinkat / renameat / readlinkat / futimens / fstatat /
dup) migrated as well. Tracked as W46 Phase 1b+.
Restructures each pfd helper as a `switch (comptime builtin.os.tag)`
so the Mac `std.c.*` arm is not semantically analyzed on Linux or
Windows builds — a prerequisite for eventually dropping
`link_libc = true` without tripping "dependency on libc must be
explicitly specified" errors.
Verified: `zig build test` (Mac aarch64), `zig build
-Dtarget=x86_64-linux-gnu`, `zig build -Dtarget=x86_64-windows-gnu`
all succeed on the initial build. Full CI to follow.
This was referenced Apr 24, 2026
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Summary
First step toward the W46 un-link-libc migration. Linux branch of
platform.pfd*helpers now callsstd.os.linux.{write,read,pread,pwrite,lseek,close,fsync}directly instead of going through libc wrappers (std.c.*). Mac/BSD keepstd.c.*(libSystem auto-links), Windows keeps the Win32 path added in #45.Behavior preserved via errno mirroring: the Linux branch writes the syscall errno into
std.c._errno().*so callers that readcErrnoToWasi()continue to observe correct error codes during the transition.Restructured as
switch (comptime builtin.os.tag)so the Mac arm isn't semantically analyzed on Linux/Windows builds — prerequisite for later droppinglink_libc = true.What this does NOT do yet
link_libc = truein build.zig unchanged).mkdirat/unlinkat/renameat/readlinkat/futimens/fstatat/dup) still usestd.c.*directly, not gated. Those become W46 Phase 1b.link_libc.Test plan
zig build teston Mac aarch64 (all pass).zig build -Dtarget=x86_64-linux-gnuclean.zig build -Dtarget=x86_64-windows-gnuclean.Tracking:
.dev/checklist.md→ W46 (planned for zwasm-cleanup merge).