mirror of
https://github.com/microsoft/vcpkg.git
synced 2024-12-25 06:37:49 +08:00
93 lines
2.5 KiB
Markdown
93 lines
2.5 KiB
Markdown
# Selecting Library Features
|
|
|
|
**The latest version of this documentation is available on [GitHub](https://github.com/Microsoft/vcpkg/tree/master/docs/users/selecting-library-features.md).**
|
|
|
|
## Installing a library
|
|
|
|
We will look at [llvm](https://llvm.org/) as an example. You could install it using:
|
|
|
|
```powershell
|
|
> vcpkg install llvm
|
|
```
|
|
or via a manifest with
|
|
```json
|
|
{
|
|
"dependencies": ["llvm"]
|
|
}
|
|
```
|
|
|
|
With llvm now installed, we can execute:
|
|
|
|
```powershell
|
|
> installed\x86-windows\bin\llc.exe --version
|
|
```
|
|
|
|
we see:
|
|
|
|
```powershell
|
|
Registered Targets:
|
|
x86 - 32-bit X86: Pentium-Pro and above
|
|
x86-64 - 64-bit X86: EM64T and AMD64
|
|
```
|
|
|
|
## Installing additional features
|
|
|
|
But [llvm supports many more targets](https://llvm.org/docs/GettingStarted.html#local-llvm-configuration), from ARM to SPARC to SystemZ.
|
|
However, clearly our current installation doesn't include ARM as a target;
|
|
thus, we need to learn how vcpkg allows us to install other LLVM targets.
|
|
The llvm port allows this via the "target-*" features.
|
|
|
|
If we do:
|
|
|
|
```powershell
|
|
> vcpkg search llvm
|
|
```
|
|
|
|
We can see:
|
|
|
|
```
|
|
llvm 10.0.0#6 The LLVM Compiler Infrastructure
|
|
llvm[clang] Build C Language Family Front-end.
|
|
llvm[clang-tools-extra] Build Clang tools.
|
|
...
|
|
llvm[target-all] Build with all backends.
|
|
llvm[target-amdgpu] Build with AMDGPU backend.
|
|
llvm[target-arm] Build with ARM backend.
|
|
...
|
|
```
|
|
|
|
We can install any of these targets by using the install-feature syntax:
|
|
|
|
```powershell
|
|
> vcpkg install llvm[target-arm] # Installs LLVM with the ARM target
|
|
```
|
|
```json
|
|
{
|
|
"dependencies": [{ "name": "llvm", "features": ["target-arm"] }]
|
|
}
|
|
```
|
|
|
|
## Opting out of default features
|
|
|
|
The llvm port includes a few default features that you as a user may not want: for example,
|
|
the `clang` feature is default, which means that `vcpkg install llvm` will also build and install clang.
|
|
If you are writing a compiler that uses LLVM as a backend,
|
|
you're likely not interested in installing clang as well,
|
|
and we can do that by disabling default features with the special `core` "feature":
|
|
```powershell
|
|
> vcpkg install llvm[core,target-arm] # removing the default-feature with "core" also removes all of the default targets you get
|
|
```
|
|
or in manifest files:
|
|
```json
|
|
{
|
|
"dependencies": [{
|
|
"name": "llvm",
|
|
"default-features": false,
|
|
"features": ["target-arm"]
|
|
}]
|
|
}
|
|
```
|
|
|
|
# Further reading
|
|
- The [Feature Packages](../specifications/feature-packages.md) specification was the initial design for features.
|