Question

I was trying to know how // and " can be passed into a macro substitution as like below:

#define STR(str) #str

while invoking STR(hel"lo) or STR(hel//lo).
This gives error. Is there any way to pass these into a macro?

Answer 1

There is no way to pass // into a macro invocation except embedded in a string or character constant as the // marks the start of a comment-to-end-of-line. Comment stripping is done before macros are processed.

Similarly, there is no way to pass a naked double quote to a macro. The double quote is either inside a character constant or marks the start of a string.

Similarly for /* and ', with appropriate changes to the reasoning.