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132 lines
4.2 KiB
132 lines
4.2 KiB
<a id="top"></a>
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# Supplying main() yourself
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**Contents**<br>
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[Let Catch take full control of args and config](#let-catch-take-full-control-of-args-and-config)<br>
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[Amending the config](#amending-the-config)<br>
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[Adding your own command line options](#adding-your-own-command-line-options)<br>
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[Version detection](#version-detection)<br>
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The easiest way to use Catch is to let it supply ```main()``` for you and handle configuring itself from the command line.
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This is achieved by writing ```#define CATCH_CONFIG_MAIN``` before the ```#include "catch.hpp"``` in *exactly one* source file.
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Sometimes, though, you need to write your own version of main(). You can do this by writing ```#define CATCH_CONFIG_RUNNER``` instead. Now you are free to write ```main()``` as normal and call into Catch yourself manually.
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You now have a lot of flexibility - but here are three recipes to get your started:
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## Let Catch take full control of args and config
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If you just need to have code that executes before and/ or after Catch this is the simplest option.
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```c++
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#define CATCH_CONFIG_RUNNER
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#include "catch.hpp"
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int main( int argc, char* argv[] ) {
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// global setup...
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int result = Catch::Session().run( argc, argv );
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// global clean-up...
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return result;
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}
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```
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## Amending the config
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If you still want Catch to process the command line, but you want to programmatically tweak the config, you can do so in one of two ways:
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```c++
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#define CATCH_CONFIG_RUNNER
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#include "catch.hpp"
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int main( int argc, char* argv[] )
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{
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Catch::Session session; // There must be exactly one instance
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// writing to session.configData() here sets defaults
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// this is the preferred way to set them
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int returnCode = session.applyCommandLine( argc, argv );
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if( returnCode != 0 ) // Indicates a command line error
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return returnCode;
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// writing to session.configData() or session.Config() here
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// overrides command line args
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// only do this if you know you need to
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int numFailed = session.run();
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// numFailed is clamped to 255 as some unices only use the lower 8 bits.
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// This clamping has already been applied, so just return it here
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// You can also do any post run clean-up here
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return numFailed;
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}
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```
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Take a look at the definitions of Config and ConfigData to see what you can do with them.
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To take full control of the config simply omit the call to ```applyCommandLine()```.
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## Adding your own command line options
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Catch embeds a powerful command line parser called [Clara](https://github.com/philsquared/Clara).
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As of Catch2 (and Clara 1.0) Clara allows you to write _composable_ option and argument parsers,
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so extending Catch's own command line options is now easy.
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```c++
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#define CATCH_CONFIG_RUNNER
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#include "catch.hpp"
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int main( int argc, char* argv[] )
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{
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Catch::Session session; // There must be exactly one instance
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int height = 0; // Some user variable you want to be able to set
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// Build a new parser on top of Catch's
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using namespace Catch::clara;
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auto cli
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= session.cli() // Get Catch's composite command line parser
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["-g"]["--height"] // the option names it will respond to
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("how high?"); // description string for the help output
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// Now pass the new composite back to Catch so it uses that
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session.cli( cli );
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// Let Catch (using Clara) parse the command line
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int returnCode = session.applyCommandLine( argc, argv );
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if( returnCode != 0 ) // Indicates a command line error
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return returnCode;
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// if set on the command line then 'height' is now set at this point
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if( height > 0 )
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std::cout << "height: " << height << std::endl;
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return session.run();
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}
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```
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See the [Clara documentation](https://github.com/philsquared/Clara/blob/master/README.md) for more details.
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## Version detection
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Catch provides a triplet of macros providing the header's version,
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* `CATCH_VERSION_MAJOR`
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* `CATCH_VERSION_MINOR`
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* `CATCH_VERSION_PATCH`
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these macros expand into a single number, that corresponds to the appropriate
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part of the version. As an example, given single header version v2.3.4,
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the macros would expand into `2`, `3`, and `4` respectively.
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---
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[Home](Readme.md#top)
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