is it possible to concatenate strings during preprocessing?
I found this example
#define H \"Hello \"
#define W \"World!\"
#define HW H W
printf(HW)
I just thought I would add an answer that cites the source as to why this works.
The C99 standard §5.1.1.2 defines translation phases for C code. Subsection 6 states:
- Adjacent string literal tokens are concatenated.
Similarly, in the C++ standards (ISO 14882) §2.1 defines the Phases of translation. Here Subsection 6 states:
6 Adjacent ordinary string literal tokens are concatenated. Adjacent wide string literal tokens are concatenated.
This is why you can concatenate strings simply by placing them adjacent to one another:
printf("string"" one\n");
>> ./a.out
>> string one
The preprocessing part of the question is simply the usage of the #define
preprocessing directive which does the substitution from identifier (H
) to string ("Hello "
).