Special thanks to @retep998 for the [excellent writeup](https://github.com/rust-lang/rfcs/issues/1061) of tasks to be done and @ricky26 for initially blazing the trail here!
# MSVC Support
This goal of this series of commits is to add MSVC support to the Rust compiler
and build system, allowing it more easily interoperate with Visual Studio
installations and native libraries compiled outside of MinGW.
The tl;dr; of this change is that there is a new target of the compiler,
`x86_64-pc-windows-msvc`, which will not interact with the MinGW toolchain at
all and will instead use `link.exe` to assemble output artifacts.
## Why try to use MSVC?
With today's Rust distribution, when you install a compiler on Windows you also
install `gcc.exe` and a number of supporting libraries by default (this can be
opted out of). This allows installations to remain independent of MinGW
installations, but it still generally requires native code to be linked with
MinGW instead of MSVC. Some more background can also be found in #1768 about the
incompatibilities between MinGW and MSVC.
Overall the current installation strategy is quite nice so long as you don't
interact with native code, but once you do the usage of a MinGW-based `gcc.exe`
starts to get quite painful.
Relying on a nonstandard Windows toolchain has also been a long-standing "code
smell" of Rust and has been slated for remedy for quite some time now. Using a
standard toolchain is a great motivational factor for improving the
interoperability of Rust code with the native system.
## What does it mean to use MSVC?
"Using MSVC" can be a bit of a nebulous concept, but this PR defines it as:
* The build system for Rust will build as much code as possible with the MSVC
compiler, `cl.exe`.
* The build system will use native MSVC tools for managing archives.
* The compiler will link all output with `link.exe` instead of `gcc.exe`.
None of these are currently implemented today, but all are required for the
compiler to fluently interoperate with MSVC.
## How does this all work?
At the highest level, this PR adds a new target triple to the Rust compiler:
x86_64-pc-windows-msvc
All logic for using MSVC or not is scoped within this triple and code can
conditionally build for MSVC or MinGW via:
#[cfg(target_env = "msvc")]
It is expected that auto builders will be set up for MSVC-based compiles in
addition to the existing MinGW-based compiles, and we will likely soon start
shipping MSVC nightlies where `x86_64-pc-windows-msvc` is the host target triple
of the compiler.
# Summary of changes
Here I'll explain at a high level what many of the changes made were targeted
at, but many more details can be found in the commits themselves. Many thanks to
@retep998 for the excellent writeup in rust-lang/rfcs#1061 and @rick26 for a lot
of the initial proof-of-concept work!
## Build system changes
As is probably expected, a large chunk of this PR is changes to Rust's build
system to build with MSVC. At a high level **it is an explicit non goal** to
enable building outside of a MinGW shell, instead all Makefile infrastructure we
have today is retrofitted with support to use MSVC instead of the standard MSVC
toolchain. Some of the high-level changes are:
* The configure script now detects when MSVC is being targeted and adds a number
of additional requirements about the build environment:
* The `--msvc-root` option must be specified or `cl.exe` must be in PATH to
discover where MSVC is installed. The compiler in use is also required to
target x86_64.
* Once the MSVC root is known, the INCLUDE/LIB environment variables are
scraped so they can be reexported by the build system.
* CMake is required to build LLVM with MSVC (and LLVM is also configured with
CMake instead of the normal configure script).
* jemalloc is currently unconditionally disabled for MSVC targets as jemalloc
isn't a hard requirement and I don't know how to build it with MSVC.
* Invocations of a C and/or C++ compiler are now abstracted behind macros to
appropriately call the underlying compiler with the correct format of
arguments, for example there is now a macro for "assemble an archive from
objects" instead of hard-coded invocations of `$(AR) crus liboutput.a ...`
* The output filenames for standard libraries such as morestack/compiler-rt are
now "more correct" on windows as they are shipped as `foo.lib` instead of
`libfoo.a`.
* Rust targets can now depend on native tools provided by LLVM, and as you'll
see in the commits the entire MSVC target depends on `llvm-ar.exe`.
* Support for custom arbitrary makefile dependencies of Rust targets has been
added. The MSVC target for `rustc_llvm` currently requires a custom `.DEF`
file to be passed to the linker to get further linkages to complete.
## Compiler changes
The modifications made to the compiler have so far largely been minor tweaks
here and there, mostly just adding a layer of abstraction over whether MSVC or a
GNU-like linker is being used. At a high-level these changes are:
* The section name for metadata storage in dynamic libraries is called `.rustc`
for MSVC-based platorms as section names cannot contain more than 8
characters.
* The implementation of `rustc_back::Archive` was refactored, but the
functionality has remained the same.
* Targets can now specify the default `ar` utility to use, and for MSVC this
defaults to `llvm-ar.exe`
* The building of the linker command in `rustc_trans:🔙:link` has been
abstracted behind a trait for the same code path to be used between GNU and
MSVC linkers.
## Standard library changes
Only a few small changes were required to the stadnard library itself, and only
for minor differences between the C runtime of msvcrt.dll and MinGW's libc.a
* Some function names for floating point functions have leading underscores, and
some are not present at all.
* Linkage to the `advapi32` library for crypto-related functions is now
explicit.
* Some small bits of C code here and there were fixed for compatibility with
MSVC's cl.exe compiler.
# Future Work
This commit is not yet a 100% complete port to using MSVC as there are still
some key components missing as well as some unimplemented optimizations. This PR
is already getting large enough that I wanted to draw the line here, but here's
a list of what is not implemented in this PR, on purpose:
## Unwinding
The revision of our LLVM submodule [does not seem to implement][llvm] does not
support lowering SEH exception handling on the Windows MSVC targets, so
unwinding support is not currently implemented for the standard library (it's
lowered to an abort).
[llvm]: https://github.com/rust-lang/llvm/blob/rust-llvm-2015-02-19/lib/CodeGen/Passes.cpp#L454-L461
It looks like, however, that upstream LLVM has quite a bit more support for SEH
unwinding and landing pads than the current revision we have, so adding support
will likely just involve updating LLVM and then adding some shims of our own
here and there.
## dllimport and dllexport
An interesting part of Windows which MSVC forces our hand on (and apparently
MinGW didn't) is the usage of `dllimport` and `dllexport` attributes in LLVM IR
as well as native dependencies (in C these correspond to
`__declspec(dllimport)`).
Whenever a dynamic library is built by MSVC it must have its public interface
specified by functions tagged with `dllexport` or otherwise they're not
available to be linked against. This poses a few problems for the compiler, some
of which are somewhat fundamental, but this commit alters the compiler to attach
the `dllexport` attribute to all LLVM functions that are reachable (e.g. they're
already tagged with external linkage). This is suboptimal for a few reasons:
* If an object file will never be included in a dynamic library, there's no need
to attach the dllexport attribute. Most object files in Rust are not destined
to become part of a dll as binaries are statically linked by default.
* If the compiler is emitting both an rlib and a dylib, the same source object
file is currently used but with MSVC this may be less feasible. The compiler
may be able to get around this, but it may involve some invasive changes to
deal with this.
The flipside of this situation is that whenever you link to a dll and you import
a function from it, the import should be tagged with `dllimport`. At this time,
however, the compiler does not emit `dllimport` for any declarations other than
constants (where it is required), which is again suboptimal for even more
reasons!
* Calling a function imported from another dll without using `dllimport` causes
the linker/compiler to have extra overhead (one `jmp` instruction on x86) when
calling the function.
* The same object file may be used in different circumstances, so a function may
be imported from a dll if the object is linked into a dll, but it may be
just linked against if linked into an rlib.
* The compiler has no knowledge about whether native functions should be tagged
dllimport or not.
For now the compiler takes the perf hit (I do not have any numbers to this
effect) by marking very little as `dllimport` and praying the linker will take
care of everything. Fixing this problem will likely require adding a few
attributes to Rust itself (feature gated at the start) and then strongly
recommending static linkage on Windows! This may also involve shipping a
statically linked compiler on Windows instead of a dynamically linked compiler,
but these sorts of changes are pretty invasive and aren't part of this PR.
## CI integration
Thankfully we don't need to set up a new snapshot bot for the changes made here as our snapshots are freestanding already, we should be able to use the same snapshot to bootstrap both MinGW and MSVC compilers (once a new snapshot is made from these changes).
I plan on setting up a new suite of auto bots which are testing MSVC configurations for now as well, for now they'll just be bootstrapping and not running tests, but once unwinding is implemented they'll start running all tests as well and we'll eventually start gating on them as well.
---
I'd love as many eyes on this as we've got as this was one of my first interactions with MSVC and Visual Studio, so there may be glaring holes that I'm missing here and there!
cc @retep998, @ricky26, @vadimcn, @klutzy
r? @brson
Building with `--target=mipsel-unknown-linux-gnu` currently results in the following errors, fixed by this PR:
```
rustc: x86_64-unknown-linux-gnu/stage2/lib/rustlib/mipsel-unknown-linux-gnu/lib/libstd
/vol/rust/src/libstd/os/linux/raw.rs:76:21: 76:28 error: use of undeclared type name `c_ulong`
/vol/rust/src/libstd/os/linux/raw.rs:76 pub st_dev: c_ulong,
^~~~~~~
/vol/rust/src/libstd/os/linux/raw.rs:83:22: 83:29 error: use of undeclared type name `c_ulong`
/vol/rust/src/libstd/os/linux/raw.rs:83 pub st_rdev: c_ulong,
^~~~~~~
/vol/rust/src/libstd/sys/common/net2.rs:210:52: 210:70 error: unresolved name `libc::TCP_KEEPIDLE`
/vol/rust/src/libstd/sys/common/net2.rs:210 setsockopt(&self.inner, libc::IPPROTO_TCP, libc::TCP_KEEPIDLE,
```
These constants were added in 6f54ce9aa5 and
e8fbd1ce04 to a consts module that is behind a
gate.
I have not confirmed that these constants do indeed work on either OSX or iOS.
It appears that some of the constants may actually belong in a POSIX module,
but I didn't make these changes here because I don't have access to the POSIX
standard.
PR #24611 added these for other architectures, but missed
the `#[cfg(any(target_arch = "mips", target_arch = "mipsel"))]`
version of the module. The values are the same.
This commit modifies the standard library and its dependencies to link correctly
when built against MUSL. This primarily ensures that the right libraries are
linked against and when they're linked against they're linked against
statically.
This patch adds a `Debug` impl for `std::fs::File`.
On all platforms (Unix and Windows) it shows the file descriptor.
On Linux, it displays the path and access mode as well.
Ideally we should show the path/mode for all platforms, not just Linux,
but this will do for now.
cc #24570
This is probably more broadly applicable than these two platforms
(since it's part of the bsd4.4 standard) but that's outside my problem domain today.
If this goes well, I may submit Linux/64 support in a separate PR.
Reviewers should take a look at http://www.opensource.apple.com/source/xnu/xnu-792.17.14/bsd/sys/socket.h?txt
which defines constants for OSX. iOS uses the same header.
I release this patch under the MIT license.
Hopefully didn’t miss or mess up anything.
~~EDIT: ah, as usual, just didn’t bother running build before pushing a submit request button. Build pending.~~
The alignment field is actually a "pointer sized" type instead of always i64,
requiring that the size of the padding field is also calculated slightly
differently.
Closes#23425
To the correct MAP_NORESERVE. Every other thing is known as MAP_NORESERVE, so this is just a basic typo.
I really doubt this will break anybody's but my own code.
This separates definitions of struct stat and other typedefs between Android and Linux on ARM (Android has a non-standard one). This makes functions such as `File::metadata()` work correctly and makes one able to check file's size. All tests from std (and also run-pass: stat.rs) now pass on ARM Linux. Fixes#20007.
According to Apple's [arm64 calling convention](https://developer.apple.com/library/ios/documentation/Xcode/Conceptual/iPhoneOSABIReference/Articles/ARM64FunctionCallingConventions.html#//apple_ref/doc/uid/TP40013702-SW1) varargs always are passed
through stack. Since `open` is actually a vararg function on Darwin,
it means that older declaration caused permissions to be taken from
stack, while passed through register => it set file permissions
to garbage and it was simply impossible to read/delete files after they
were created.
They way this commit handles it is to preserve compatibility with
existing code - it simply creates a shim unsafe function so all existing
callers continue work as nothing happened.
According to Apple arm64 calling convention varargs always are passed
through stack. Since `open` is actually a vararg function on Darwin's,
it means that older declaration caused permissions to be taken from
stack, while passed through register => it set file permissions
to garbage and it was simply impossible to read/delete files after they
were created.
They way this commit handles it is to preserve compatibility with
existing code - it simply creates a shim unsafe function so all existing
callers continue work as nothing happened.
Automatic has-same-types testing methodology can be found in #22501.
Because most of them don't work with `--pretty=typed`, compile-fail tests were manually audited.
r? @aturon
This same source is being built in the Cargo ecosystem and hence needs to build
on stable Rust as well. This commit places the `no_std` attribute along with the
`no_std` feature behind a `cfg_attr` flag so they are not processed when
compiled on crates.io
