How to convert a string to variable name using macro?

Question

#define TRACE(arg1,...)  char* arg1; 

int main(void)
{
    int a=4;
    TRACE(("Hello",a));  // convert "Hello" to a valid char variable name.
    return 0;
}

I'm having trouble in converting the string "Hello" into a variable name. for example: "Hello" should be converted as const char* Hello; by using a macro. Since there are double quotes I'm unable to convert it. This is my first question in Stack Overflow.

yAlso, here your TRACE has exactly one macro argument: arg1 is bound to ("Hello",a). — Antti Haapala
– Antti Haapala, Commented Jun 21, 2018 at 7:12
since TRACE(Hello) is used in another macro am using as TRACE(("Hello")) and more over , can use printf function. So I'm retaining it. — w.jayson
– w.jayson, Commented Jun 21, 2018 at 7:19
what do you mean by "used in another macro" ? What do you mean by "can use printf function" ? Can you show code for both to clarify what you want to achieve and what your restrictions are ? — Sander De Dycker
– Sander De Dycker, Commented Jun 21, 2018 at 7:55
#define SMM_TRACE(x) printf x #define SMM_TRACE_CONVERT SMM_TRACE(CONVERT_ERROR_KEY_FAILED) int main() { int num = 1; SMM_TRACE(("the number is %d\n", num)); printf("%s","SMM_TRACE_CONVERT\n"); return 0; } — w.jayson
– w.jayson, Commented Jun 21, 2018 at 9:42

Jens · Accepted Answer · 2018-06-21 07:10:57Z

7

You can't "destringify" a string in C.

You can stringify a token, though, so the solution is to do it the other way around: use the token hello and stringify it when you need "hello".

answered Jun 21, 2018 at 7:10

Jens

73.3k16 gold badges134 silver badges186 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

w.jayson Over a year ago

ok I will use the token hello and I ll stringify it when needed. another problem is the inner parenthesis (). With parentheses (hello) will not be a variable. How to avoid this. is there any way to eliminate this.

Jens Over a year ago

@w.jayson You should search for "c variadic macros" if that is what you need. They are part of the C language starting with C99. See, e.g., en.wikipedia.org/wiki/Variadic_macro

w.jayson Over a year ago

Yes, am trying to implement variadic macros. The only thing I dint get is, is it possible to use #define TRACE((arg1,...)) instead of #define TRACE(arg1,...) so that I can easily avoid the restrictions.

w.jayson · Accepted Answer · 2018-06-21 13:17:56Z

0

Thank you all of you for spending your valuable time to respond my question. Some of your comments gave me an idea to sort out the answer. you can find the answer below :

#define TRACE(arg1,...)  TRACE2 arg1
#define TRACE2(arg1, arg2) static const char arg1; \
                             printf("%p\n",(void*)&arg1);\
                              printf("%d\n",arg2);\

If any changes can be done in this code, kindly let me know.

answered Jun 21, 2018 at 13:17

w.jayson

371 silver badge5 bronze badges

1 Comment

Jonathan Leffler Over a year ago

@Jens: if the invocation of TRACE has double parentheses as in the question, this is OK.

Collectives™ on Stack Overflow

How to convert a string to variable name using macro?

2 Answers 2

3 Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related