Question

For a lot of function calls in a C app that needs some degree of debugging I wanted to add a macro to ease the typing that I had to do.

right now I am calling a function like this:

aDebugFunction(&ptrToFunction, __LINE__, "ptrToFunction", param1, param2, etc)

So I thought lets write a macro that does the first 3 parameters for me, like this:

#define SOMEDEFINE(x) &x, __LINE__,  "x"

However, as most of you will immediately know, this won’t work it won’t replace “x” with the name that x has been given but will just pass “x” as 3rd parameter.

My knowledge of this preprocessor macro happening stuff is quite limited and thus my googling-ability is also quite useless due to not knowing where to search for exactly.

I hope one of you guys/girls could give me either a solution or point me in the right direction.

Answer 1

You need to use the # convert token to string command of the preprocessor. You should define your second macro this way:

#define SOMEDEFINE(x) &x, __LINE__,  # x

Or if x can also be a macro call, and you want the string to contains the expansion of the macro, you need to use an auxiliary macro:

#define TOKEN_TO_STRING(TOK) # TOK
#define STRINGIZE_TOKEN(TOK) TOKEN_TO_STRING(TOK)
#define SOMEDEFINE(x) &x, __LINE__, STRINGIZE_TOKEN(x)

For example, if you have the following code:

#define SHORT_NAME a_very_very_very_long_variable_name
SOMEDEFINE(SHORT_NAME)

Then, with the first macro, it will expand to

&a_very_very_very_long_variable_name, __LINE__, "SHORT_NAME"

While, with the second macro, it will expand to:

&a_very_very_very_long_variable_name, __LINE__, "a_very_very_very_long_variable_name"