* Add a `getpagesize` function.
This adds a `getpagesize` function. This interface is deprecated in POSIX,
but it's sufficiently widely used and not problematic in practice.
* Use musl's `getpagesize`.
* Enable the `getpagesize` declaration in unistd.h.
* Add basic emulation of getcwd/chdir
This commit adds basic emulation of a current working directory to
wasi-libc. The `getcwd` and `chdir` symbols are now implemented and
available for use. The `getcwd` implementation is pretty simple in that
it just copies out of a new global, `__wasilibc_cwd`, which defaults to
`"/"`. The `chdir` implementation is much more involved and has more
ramification, however.
A new function, `make_absolute`, was added to the preopens object. Paths
stored in the preopen table are now always stored as absolute paths
instead of relative paths, and initial relative paths are interpreted as
being relative to `/`. Looking up a path to preopen now always turns it
into an absolute path, relative to the current working directory, and an
appropriate path is then returned.
The signature of `__wasilibc_find_relpath` has changed as well. It now
returns two path components, one for the absolute part and one for the
relative part. Additionally the relative part is always dynamically
allocated since it may no longer be a substring of the original input
path.
This has been tested lightly against the Rust standard library so far,
but I'm not a regular C developer so there's likely a few things to
improve!
* Amortize mallocs made in syscalls
* Avoid size bloat on programs that don't use `chdir`
* Add threading compat
* Collect `link`/`renameat` second path lookup
* Update comments about chdir.c in makefile
* Move definition of `__wasilibc_find_relpath_alloc` to header
* Expand comments
* Document the format of strings a bit more
* Fixup a few issues in path logic
* Fix GitHub Actions
* Avoid calling `poll_oneoff` with zero subscriptions.
With https://github.com/WebAssembly/WASI/pull/193 merged, WASI is moving
to make `poll_oneoff` with no arguments an error. Even though that's in
ephemeral and not yet in a snapshot, we can start to anticipate it in
libc:
- Remove the `pause` function, since WASI has no signals and thus no
way to ever wake it up short of having the host terminate it.
- Make `poll` and `pselect` return `ENOTSUP` in the case of having no
events to wait for.
* Remove `pause` from the defined-symbols.txt list.
* Fix __wasilibc_unmodified_upstream markers.
* Check for zero subscriptions, rather than zero events.
Make `poll` and `pselect` return `ENOTSUP` when asked to poll on zero
subscriptions, rather than when the systerm returns zero events.
While here, drop the `__wasilibc_unmodified_upstream` markers, which
were already pretty noisy here, and would be significantly worse with
this change.
* Add comments about the subtle relationship between nfds and nsubscriptions.
* Rewrite the comment.
* Fix code quotes.
See the WHATSNEW file for details; this doesn't have any major changes
for wasi-libc; in particular, the new catgets and GLOB_TILDE features
are disabled.
The lseek optimization turns lseek calls into __wasilibc_tell calls when
possible, using macros and __builtin_constant_p. However, this isn't
safe in C++ code in the presence of namespaces and `using` declarations,
to just disable it in C++ for now.
`lseek(x, 0, SEEK_CUR)` has no effect other than to return the current
file offset. The patch here uses a macro with `__builtin_constant_p` to
recognize this case and rewrite it to a library call that uses `fd_tell`
rather than `fd_seek`, so that programs that don't need actual seeking
don't end up importing `fd_seek`.
This is also the first usage of `__wasi_fd_tell` in WASI libc, so this
adds it to undefined-symbols.txt.
And clean up various stale declarations and macros that this turned up.
In particular:
- Don't install pthread.h or aio.h in THREAD_MODEL=single mode.
- Don't define mkstemp and friends, since WASI currently has no support for
temporary directories.
Add at least a one-line comment on every
`#ifdef __wasilibc_unmodified_upstream` briefly indicating what its
purpose is.
While here, reenable some of the code that was previously disabled when
getenv wasn't supported, as getenv is now supported.
