Quoting the contents of a #define

**octangle** · 01-10-2007

I want to print the contents of a VC Preprocessor Definition (essentially a #define set by the IDE - such as X=ABC).

When I do the following:

printf("%s", X);

I get the compiler error:

error C2065: 'ABC': undeclared identifier

This makes sense to me... but the net effect that I want to acheive is

printf("%s", "X"); /* Where the preprocessor define X resolves to value ABC */

You might think why am I being so dense - by not simply hard code "ABC" since I'm setting this value statically within the VC IDE... The effect would be the same...

Well - I need to compile this code on mulitple O/S'es and want the value of X to be set by my build script...

**dwks** · 01-10-2007

Use the "stringize" operator.

Code:

#define debug_long(x) \
    printf(#x " = %li\n", x)

It turns an argument into a string representing the argument. Passing the above macro var would result in

Code:

printf("var" " = %li\n", var);

or

Code:

printf("var = %li\n", var);

[edit] See the section "Quoting the Macro Arguments" in this wikipedia entry: http://en.wikipedia.org/wiki/C_preprocessor [/edit]

**octangle** · 01-10-2007

What you've offered will produce the following:

"X" (the name of the #define) not "ABC" (the value of the #define)...

I want the value contained within X to be stringized

**dwks** · 01-10-2007

That's exactly what happens, unless I'm misunderstanding you.

Code:

#define def(X) puts(#X)

def(ABC);
/* is the same as */
puts("ABC");

**octangle** · 01-10-2007

QUESTION
How do I convert a constant passed to a #define macro into a text string?

ANSWER
Pass the parameter to a stringizing macro as shown below:

#define NUMBER B85800 // this can be defined in the command line

#define VAL(str) #str
#define TOSTRING(str) VAL(str)

unsigned char part1[10] = TOSTRING (NUMBER); // generates "B85800"
unsigned char part2[10] = VAL(NUMBER); // generates "NUMBER"

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Answer found... sorry to have trouble you...

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