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ES.33: another warning against macros

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Bjarne Stroustrup 2015-12-05 18:33:36 -05:00
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@ -7230,6 +7230,7 @@ Declaration rules:
* [ES.30: Don't use macros for program text manipulation](#Res-macros)
* [ES.31: Don't use macros for constants or "functions"](#Res-macros2)
* [ES.32: Use `ALL_CAPS` for all macro names](#Res-ALL_CAPS)
* [ES.33: If you must use macros, give them unique names](#Res-MACROS)
* [ES.40: Don't define a (C-style) variadic function](#Res-ellipses)
Expression rules:
@ -8165,6 +8166,28 @@ Convention. Readability. Distinguishing macros.
Scream when you see a lower case macro.
### <a name="Res-MACROS"></a> ES.33: If you must use macros, give them unique names
##### Reason
Macros do not obey scope rules.
##### Example
#define MYCHAR /* BAD, will eventually clash with someone else's MYCHAR*/
#define ZCORP_CHAR /* Still evil, but less likely to clash */
##### Note
Avoid macros if you can: [ES.30](#Res-macros), [ES.31](#Res-macros2), and [ES.32](#Res-ALL_CAPS).
However, there are billions of lines of code literated with macros and a long tradition for using and overusing macros.
If you are forced to use macros, use long names and supposedly unique prefixes (e.g., your organization's name) to lower the likelyhood of a clash.
##### Enforcement
Warn against short macro names.
### <a name="Res-ellipses"></a> ES.40: Don't define a (C-style) variadic function
##### Reason