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41 lines
2.1 KiB
Markdown
41 lines
2.1 KiB
Markdown
## Extending limits
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The `ENUM` macro makes heavy use of the preprocessor, and some of the internal
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macros have size limits. There are two: on the number of constants you can
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declare, and on the maximum length of a constant name under very specific
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conditions. If you run into either one, you can extend the limit by following
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the instructions on this page.
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The second limit, on the maximum length of a constant name, applies only when
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you are compiling an enum in
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["full" `constexpr`](${prefix}OptInFeatures.html#CompileTimeNameTrimming) mode
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*and* the constant has an initializer. Otherwise, your constants can have names
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of arbitrary length.
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The default limits are 64 constants in an enum and 23 characters for initialized
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constants of full-`constexpr` enums. To extend:
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1. Pick your desired limits. I will use 512 constants and 63 characters as an
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example. Add 1 to the number of characters to account for the null
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terminator — our numbers are now 512 and 64.
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2. Get `make_macros.py` from your copy of the full Better Enums distribution
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or from <a href="https://raw.githubusercontent.com/aantron/better-enums/$version/script/make_macros.py" download>GitHub</a>.
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3. You will run this script to generate a header file containing some
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replacement macros for `enum.h` to use. Pick a name for this file and a
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location somewhere in your include path. I will assume that this file is
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`common/enum_macros.h` in your project.
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4. Run `python make_macros.py 512 64 > common/enum_macros.h`.
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5. Define `BETTER_ENUMS_MACRO_FILE <common/enum_macros.h>` before including
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`enum.h`. This is typically done by supplying extra flags to the compiler
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on the command line:
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- For g++ and clang++, `-DBETTER_ENUMS_MACRO_FILE='<common/enum_macros.h>'`
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- For VC++, `\DBETTER_ENUMS_MACRO_FILE='<common/enum_macros.h>'`
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6. Enjoy the looser limits. Just watch out — increasing the second
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number can really slow down compilation of full-`constexpr` enums.
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7. You don't need `make_macros.py` anymore. It's not part of your build
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process and you can delete it.
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%% description = How to extend limits imposed by internal macros.
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