C Preprocessor, Stringify the result of a macro
I want to stringify the result of a macro expansion.
I've tried with the following:
#define QUOTE(str) #str
#d开发者_如何转开发efine TEST thisisatest
#define TESTE QUOTE(TEST)
And TESTE gets expanded to: "TEST", while I'm trying to get "thisisatest". I know this is the correct behavior of the preprocessor but can anyone help me with a way to achieve the other one?
Using TESTE #TEST is not valid
Using TESTE QUOTE(thisisatest) is not what I'm trying to do
Like this:
#include <stdio.h>
#define QUOTE(str) #str
#define EXPAND_AND_QUOTE(str) QUOTE(str)
#define TEST thisisatest
#define TESTE EXPAND_AND_QUOTE(TEST)
int main() {
printf(TESTE);
}
The reason is that when macro arguments are substituted into the macro body, they are expanded unless they appear with the # or ## preprocessor operators in that macro. So, str
(with value TEST
in your code) isn't expanded in QUOTE
, but it is expanded in EXPAND_AND_QUOTE
.
To clarify a bit more, essentially the preprocessor was made to execute another "stage". i.e :
1st case:
->TESTE
->QUOTE(TEST) # preprocessor encounters QUOTE
# first so it expands it *without expanding its argument*
# as the '#' symbol is used
->TEST
2nd case:
->TESTE
->EXPAND_AND_QUOTE(TEST)
->QUOTE(thisisatest)
# after expanding EXPAND_AND_QUOTE
# in the previous line
# the preprocessor checked for more macros
# to expand, it found TEST and expanded it
# to 'thisisatest'
->thisisatest
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