200 lines
6.1 KiB
Markdown
200 lines
6.1 KiB
Markdown
# Manifest Mode: CMake Example
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We would like to add vcpkg manifest support to an existing cmake project!
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Let's create a simple project that prints the fibonacci sequence up to a certain number,
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using some common dependencies.
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## Initial Layout
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Let's create the following file layout:
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```no-highlight
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fibo/
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src/
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main.cxx
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CMakeLists.txt
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```
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And we wish to use [fmt](https://github.com/fmtlib/fmt), [range-v3](https://github.com/ericniebler/range-v3),
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and [cxxopts](https://github.com/jarro2783/cxxopts).
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Let's write our `CMakeLists.txt` first:
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```cmake
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cmake_minimum_required(VERSION 3.15)
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project(fibo CXX)
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find_package(fmt REQUIRED)
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find_package(range-v3 REQUIRED)
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find_package(cxxopts REQUIRED)
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add_executable(fibo src/main.cxx)
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target_link_libraries(fibo
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PRIVATE
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fmt::fmt
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range-v3::range-v3
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cxxopts::cxxopts)
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```
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And then we should add `main.cxx`:
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```cxx
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#include <cxxopts.hpp>
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#include <fmt/format.h>
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#include <range/v3/view.hpp>
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namespace view = ranges::view;
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int fib(int x) {
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int a = 0, b = 1;
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for (int it : view::repeat(0) | view::take(x)) {
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(void)it;
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int tmp = a;
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a += b;
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b = tmp;
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}
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return a;
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}
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int main(int argc, char** argv) {
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cxxopts::Options options("fibo", "Print the fibonacci sequence up to a value 'n'");
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options.add_options()
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("n,value", "The value to print to", cxxopts::value<int>()->default_value("10"));
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auto result = options.parse(argc, argv);
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auto n = result["value"].as<int>();
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for (int x : view::iota(1) | view::take(n)) {
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fmt::print("fib({}) = {}\n", x, fib(x));
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}
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}
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```
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This is a simple project of course, but it should give us a clean project to start with.
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Let's try it out!
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Let's assume you have `fmt`, `range-v3`, and `cxxopts` installed with vcpkg classic mode;
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then, you can just do a simple:
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```cmd
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D:\src\fibo> cmake -B build -S . -DCMAKE_TOOLCHAIN_FILE=D:\src\vcpkg\scripts\buildsystems\vcpkg.cmake
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-- Building for: Visual Studio 16 2019
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-- Selecting Windows SDK version 10.0.18362.0 to target Windows 10.0.19041.
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-- The CXX compiler identification is MSVC 19.27.29111.0
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-- Detecting CXX compiler ABI info
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-- Detecting CXX compiler ABI info - done
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-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/MSVC/14.27.29110/bin/Hostx64/x64/cl.exe - skipped
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-- Detecting CXX compile features
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-- Detecting CXX compile features - done
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-- Configuring done
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-- Generating done
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-- Build files have been written to: D:/src/fibo/build
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D:\src\fibo> cmake --build build
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Microsoft (R) Build Engine version 16.7.0+b89cb5fde for .NET Framework
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Copyright (C) Microsoft Corporation. All rights reserved.
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Checking Build System
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Building Custom Rule D:/src/fibo/CMakeLists.txt
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main.cxx
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The contents of <span> are available only with C++20 or later.
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fibo.vcxproj -> D:\src\fibo\build\Debug\fibo.exe
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Building Custom Rule D:/src/fibo/CMakeLists.txt
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```
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And now we can try out the `fibo` binary!
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```cmd
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D:\src\fibo> .\build\Debug\fibo.exe -n 7
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fib(1) = 1
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fib(2) = 1
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fib(3) = 2
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fib(4) = 3
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fib(5) = 5
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fib(6) = 8
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fib(7) = 13
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```
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it works!
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## Converting to Manifest Mode
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We now wish to use manifest mode, so all of our dependencies are managed for us! Let's write a `vcpkg.json`:
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```json
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{
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"name": "fibo",
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"version-string": "0.1.0",
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"dependencies": [
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"cxxopts",
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"fmt",
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"range-v3"
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]
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}
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```
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Let's delete the build directory and rerun the build:
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```cmd
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D:\src\fibo> rmdir /S /Q build
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D:\src\fibo> cmake -B build -S . -DCMAKE_TOOLCHAIN_FILE=D:\src\vcpkg\scripts\buildsystems\vcpkg.cmake
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-- Running vcpkg install
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Detecting compiler hash for triplet x64-windows...
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The following packages will be built and installed:
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cxxopts[core]:x64-windows
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fmt[core]:x64-windows
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range-v3[core]:x64-windows
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Starting package 1/3: cxxopts:x64-windows
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Building package cxxopts[core]:x64-windows...
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Using cached binary package: C:\Users\me\AppData\Local\vcpkg/archives\d2\d2d1e5302cdfefef2fd090d8eda84cc0c1fbe6f1.zip
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Building package cxxopts[core]:x64-windows... done
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Installing package cxxopts[core]:x64-windows...
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Installing package cxxopts[core]:x64-windows... done
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Elapsed time for package cxxopts:x64-windows: 50.64 ms
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Starting package 2/3: fmt:x64-windows
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Building package fmt[core]:x64-windows...
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Using cached binary package: C:\Users\me\AppData\Local\vcpkg/archives\bf\bf00d5214e912d71414b545b241f54ef87fdf6e5.zip
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Building package fmt[core]:x64-windows... done
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Installing package fmt[core]:x64-windows...
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Installing package fmt[core]:x64-windows... done
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Elapsed time for package fmt:x64-windows: 225 ms
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Starting package 3/3: range-v3:x64-windows
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Building package range-v3[core]:x64-windows...
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Using cached binary package: C:\Users\me\AppData\Local\vcpkg/archives\fe\fe2cdedef6953bf954e8ddca471bf3cc8d9b06d7.zip
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Building package range-v3[core]:x64-windows... done
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Installing package range-v3[core]:x64-windows...
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Installing package range-v3[core]:x64-windows... done
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Elapsed time for package range-v3:x64-windows: 1.466 s
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Total elapsed time: 1.742 s
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-- Running vcpkg install - done
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-- Selecting Windows SDK version 10.0.18362.0 to target Windows 10.0.19041.
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-- The CXX compiler identification is MSVC 19.27.29111.0
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-- Detecting CXX compiler ABI info
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-- Detecting CXX compiler ABI info - done
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-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/MSVC/14.27.29110/bin/Hostx64/x64/cl.exe - skipped
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-- Detecting CXX compile features
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-- Detecting CXX compile features - done
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-- Configuring done
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-- Generating done
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-- Build files have been written to: D:/src/fibo/build
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D:\src\fibo> cmake --build build
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Microsoft (R) Build Engine version 16.7.0+b89cb5fde for .NET Framework
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Copyright (C) Microsoft Corporation. All rights reserved.
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Checking Build System
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Building Custom Rule D:/src/fibo/CMakeLists.txt
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main.cxx
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The contents of <span> are available only with C++20 or later.
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fibo.vcxproj -> D:\src\fibo\build\Debug\fibo.exe
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Building Custom Rule D:/src/fibo/CMakeLists.txt
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```
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You can see that with just a _single file_, we've changed over to manifests without _any_ trouble.
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The build system doesn't change _at all_! We just add a `vcpkg.json` file, delete the build directory,
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and reconfigure. And we're done!
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