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Dragonion

A difference between typedef and #define?

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Hi

Can anyone come up with an example where you can not use this
[source]typedef int MyIntType;[/source]instead of this
[source]#define MyIntType int[/source]or vice versa for primitive data types?

Personally I would prefer a typedef since that would enable the compiler to report the correct type in case of an error, but I can actually not think of a situation where one style would have limitations compared to the other (unlike using #defines for constant values instead of declaring a const variable, for example).

EDIT: Oh yes, and besides the fact that typedefs are bound by namespaces, of course.

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As usual, #define doesn't respect syntax, and multiple tokens pasted by the preprocessor can associate in unexpected order.

[source]
typedef char * mystring_t;
#define mystring_d char *

int a,b;
mystring_t c,d;
mystring_d e,f;
[/source]
a and b are or type int.
c and d are of type char *.
e is of type char *, but f is not.

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Using a define for that is never acceptable imho.

I agree. It's ugly.

As usual, #define doesn't respect syntax, and multiple tokens pasted by the preprocessor can associate in unexpected order.

[source]
typedef char * mystring_t;
#define mystring_d char *

int a,b;
mystring_t c,d;
mystring_d e,f;
[/source]
a and b are or type int.
c and d are of type char *.
e is of type char *, but f is not.

Ah, very good point! This definitely shows that there is in fact a big difference. Thanks.

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If you are using an external library with an identifier containing "MyIntType", you could get strange and inconsistent results.

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