A strange usage of # and sizeof.

George2 · 10-18-2005, 09:07 PM

Hello everyone,

I have found a very strange usage of # and sizeof in the following statement,

Code:

#define FOO(p) static const struct_goo p = { .length = sizeof(#p "\n")};

What means "#p"? What is the meaning of the parameter -- #p "\n" -- passed to sizeof?

thanks in advance,
George

primo · 10-18-2005, 10:39 PM

#p puts whatever p is within double quotes. sizeof(#p "\n") would be sizeof("bar" "\n") with FOO(bar). Then "bar" and "\n" are concatenated by the compiler.

George2 · 10-19-2005, 12:11 AM

Thanks primo,

Quote:

Originally posted by primo
#p puts whatever p is within double quotes. sizeof(#p "\n") would be sizeof("bar" "\n") with FOO(bar). Then "bar" and "\n" are concatenated by the compiler.

I have understood your points.

regards,
George