In C, it’s common to define macros that do some stuff getting the verbatim argument, and at the same time define functions to be able to get the address of it transparently. // could evaluate at compile time if __builtin_sin gets // special treatment by the compiler #define sin(x) __builtin_sin(x) // parentheses avoid substitution by … Read more
In C, string literals are concatenated automatically. For example, const char * s1 = “foo” “bar”; const char * s2 = “foobar”; s1 and s2 are the same string. So, for your problem, the answer (without token pasting) is #ifdef __TESTING #define IV_DOMAIN “example.org” #elif __LIVE_TESTING #define IV_DOMAIN “test.example.com” #else #define IV_DOMAIN “example.com” #endif #define … Read more
No, you can’t unstringify something.
You could try typeid(T).name() Edit: Fixed based on comments.
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 … Read more
An occurrence of a parameter in a function-like macro, unless it is the operand of # or ##, is expanded before substituting it and rescanning the whole for further expansion. Because g‘s parameter is the operand of #, the argument is not expanded but instead immediately stringified (“f(1,2)”). Because h‘s parameter is not the operand … Read more
In this context (applied to a parameter reference in a macro definition), the pound sign means to expand this parameter to the literal text of the argument that was passed to the macro. In this case, if you call PRINT(5) the macro expansion will be printf(“5” “%d\n”, 5); which will print 5 5; not very … Read more
The relevant steps of macro expansion are (per C 2011 [n1570] 6.10.3.1 and C++ 1998 16.3.1): Process tokens that are preceded by # or ##. Apply macro replacement to each argument. Replace each parameter with the corresponding result of the above macro replacement. Rescan for more macros. Thus, with xstr(foo), we have: The replacement text, … Read more
see http://www.decompile.com/cpp/faq/file_and_line_error_string.htm specifically: #define STRINGIFY(x) #x #define TOSTRING(x) STRINGIFY(x) #define AT __FILE__ “:” TOSTRING(__LINE__) so your problem can be solved by doing sscanf(buf, “%” TOSTRING(MAX_LEN) “s”, val);
One thing to be aware of when you’re using the token-paste (‘##‘) or stringizing (‘#‘) preprocessing operators is that you have to use an extra level of indirection for them to work properly in all cases. If you don’t do this and the items passed to the token-pasting operator are macros themselves, you’ll get results … Read more