For `libc` types that will be initialized in FFI calls, we can just use
`MaybeUninit` and then pass around raw pointers.
For `sun_path_offset()`, which really wants `offset_of`, all callers
have a real `sockaddr_un` available, so we can use that reference.
This is a non-POSIX extension implemented in Solaris and in glibc 2.29.
With this we can still use `posix_spawn()` when `Command::current_dir()`
has been set, otherwise we fallback to `fork(); chdir(); exec()`.
This commit, after reverting #55359, applies a different fix for #46775
while also fixing #55775. The basic idea was to go back to pre-#55359
libstd, and then fix#46775 in a way that doesn't expose #55775.
The issue described in #46775 boils down to two problems:
* First, the global environment is reset during `exec` but, but if the
`exec` call fails then the global environment was a dangling pointer
into free'd memory as the block of memory was deallocated when
`Command` is dropped. This is fixed in this commit by installing a
`Drop` stack object which ensures that the `environ` pointer is
preserved on a failing `exec`.
* Second, the global environment was accessed in an unsynchronized
fashion during `exec`. This was fixed by ensuring that the
Rust-specific environment lock is acquired for these system-level
operations.
Thanks to Alex Gaynor for pioneering the solution here!
Closes#55775
Co-authored-by: Alex Gaynor <alex.gaynor@gmail.com>
Instead, pass the environment to execvpe, so the kernel can apply it directly to the new process. This avoids a use-after-free in the case where exec'ing the new process fails for any reason, as well as a race condition if there are other threads alive during the exec.
These were showing up in tests and in binaries but are trivially optimize-able
away, so add `#[inline]` attributes so LLVM has an opportunity to optimize them
out.
The expected behavior is that the environment's PATH should be used
to find the process. posix_spawn() could be used if we iterated
PATH to search for the binary to execute. For now just skip
posix_spawn() if PATH is modified.
spawn() is expected to return an error if the specified file could not be
executed. FreeBSD's posix_spawn() supports returning ENOENT/ENOEXEC if
the exec() fails, which not all platforms support. This brings a very
significant performance improvement for FreeBSD, involving heavy use of
Command in threads, due to fork() invoking jemalloc fork handlers and
causing lock contention. FreeBSD's posix_spawn() avoids this problem
due to using vfork() internally.
Remove support for the PNaCl target (le32-unknown-nacl)
This removes support for the `le32-unknown-nacl` target which is currently supported by rustc on tier 3. Despite the "nacl" in the name, the target doesn't output native code (x86, ARM, MIPS), instead it outputs binaries in the PNaCl format.
There are two reasons for the removal:
* Google [has announced](https://blog.chromium.org/2017/05/goodbye-pnacl-hello-webassembly.html) deprecation of the PNaCl format. The suggestion is to migrate to wasm. Happens we already have a wasm backend!
* Our PNaCl LLVM backend is provided by the fastcomp patch set that the LLVM fork used by rustc contains in addition to vanilla LLVM (`src/llvm/lib/Target/JSBackend/NaCl`). Upstream LLVM doesn't have PNaCl support. Removing PNaCl support will enable us to move away from fastcomp (#44006) and have a lighter set of patches on top of upstream LLVM inside our LLVM fork. This will help distribution packagers of Rust.
Fixes#42420
* Use size_t where size_t is used, while it's not critical on our
specifically supported architectures, this is more accurate.
* Update HND_SPECIAL_COUNT to the correct value, and give it the size
that enum is likely to be.
* Match definition of c_char in os/raw.rs with the libc definition
Due to historic reasons, os/raw.rs redefines types for c_char from
libc, but these didn't match. Now they do :).
* Enable signal reset on exec for L4Re
L4Re has full signal emulation and hence it needs to reset the
signal set of the child with sigemptyset. However, gid and uid
should *not* be set.
