79 lines
952 B
Markdown
79 lines
952 B
Markdown
---
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title: C Preprocessor
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category: C-like
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intro: |
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Quick reference for the [C macro preprocessor](https://en.m.wikipedia.org/wiki/C_preprocessor), which can be used independent of C/C++.
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---
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## Reference
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{: .-three-column}
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### Compiling
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```
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$ cpp -P file > outfile
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```
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### Includes
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```
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#include "file"
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```
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### Defines
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```
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#define FOO
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#define FOO "hello"
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#undef FOO
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```
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### If
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```
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#ifdef DEBUG
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console.log('hi');
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#elif defined VERBOSE
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...
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#else
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...
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#endif
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```
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### Error
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```
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#if VERSION == 2.0
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#error Unsupported
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#warning Not really supported
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#endif
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```
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### Macro
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```
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#define DEG(x) ((x) * 57.29)
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```
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### Token concat
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```
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#define DST(name) name##_s name##_t
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DST(object); #=> object_s object_t;
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```
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### Stringification
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```
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#define STR(name) #name
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char * a = STR(object); #=> char * a = "object";
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```
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### file and line
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```
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#define LOG(msg) console.log(__FILE__, __LINE__, msg)
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#=> console.log("file.txt", 3, "hey")
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```
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