~~This patch series first starts with a number of commits stubbing out
functions in the existing `THREAD_model=posix` code. According to "The
Open Group Base Specifications Issue 7, 2018 edition", there are a
number of mandatory functions which have not been provided. There are
also some optional functions that have been partially provided in a
not-useful way (e.g. get but no set function). For these, I have chosen
to clean them up and remove the get functions for consistency.~~ EDIT:
These have been split off into separate PRs and merged.
The remainder of the patches then build up a stub implementation of
pthreads for `THREAD_MODEL=single`. I have done my best to try to make
sure that all functions are as conforming as possible (under the
assumption that another thread cannot ever be launched). This means that
objects such as mutexes and rwlocks actually do update their state and
will correctly fail when locks cannot be acquired.
When an inevitable deadlock occurs, I have chosen to return EDEADLK when
it has been explicitly listed as a permissible return value, and to
invoke `__builtin_trap` otherwise.
I have tested this by rebuilding libc++ with threads enabled and then
smoke-testing Clang/LLVM-on-WASI to make sure that it can compile a
simple program. I have not run any more-extensive conformance testing.
Fixes#501
[POSIX semaphores] come in two forms: named and unnamed. Roughly, named
semaphores use files to implement locking across processes; unnamed
semaphores use a shared memory region to implement locking across
threads in the same process. Since WASI currently has no process concept
(and it is relatively unclear how to map the WASI files as shared
memory), only the unnamed semaphores are supported by this changed. This
means that `sem_open`, `sem_close`, and `sem_unlink` will not available
to programs compiled with a threads-enabled `wasi-libc`.
[POSIX semaphores]: https://man7.org/linux/man-pages/man7/sem_overview.7.html
See the WHATSNEW file for details. The biggest change in musl is the
switch to 64-bit time_t for 32-bit targets, however WASI libc was already
using 64-bit time_t. The main change affecting WASI is an update to
Unicode 12.1.0.
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.
