problem in #define

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#define A3FID(T) A3FCHUNCK_ID_##T
#define A3FNAME(T) A3FCHUNK_NAME_##T
#define A3F_ID_NAME(T) ((const unsigned long)A3FID(T)),A3FNAME(T)

Please explain above Code? IS is Macro? What may be T? It shows undefined.. but does not give any Error...

Posted 15-Mar-10 1:21am

anurag1984

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Richard MacCutchan · Answer 1 · 2010-03-15T02:09:00

Each #define statement creates a macro. The first two prefix some value with a label, and the third generates some statement for example:

A3F_ID_NAME(22)

// generates
((const unsigned long)A3FCHUNCK_ID22, A3FCHUNCK_NAME22

However, I have no idea what code this is supposed to generate without seeing more of your source. The ## operator is the token paster[^], used by the preprocessor.

r.ps · Answer 2 · 2010-03-15T02:05:00

Solution 1

Yes, they are macros that uses concatenation. The 'T' is the parameter that you pass to the macro.

e.g. a statement like "int a = A3FID(PARAM);" will translate(after preprocessing) into "int a = A3FCHUNCK_ID_PARAM;"

hope that helps.

Posted 15-Mar-10 2:05am

r.ps