Stringizing

[happy]

#include<stdio.h>
#define pstr(x) printf(#x)

int main()
{
pstr("Hello");
printf("\n");
return 0;
}

I thought that pstr("Hello") will expand to printf(""Hello"") which
will give compile error.
But it prints "Hello".
How expansion is working?

 

[Ben Bacarisse]

#include<stdio.h>
#define pstr(x) printf(#x)

int main()
{
pstr("Hello");
printf("\n");
return 0;
}

I thought that pstr("Hello") will expand to printf(""Hello"") which
will give compile error.

No, it *should* expand to printf("\"Hello\""); which is what my gcc
does.

But it prints "Hello".
How expansion is working?

That is as expected.

 

[lawrence.jones]

#include<stdio.h>
#define pstr(x) printf(#x) [...]
I thought that pstr("Hello") will expand to printf(""Hello"") which
will give compile error.
But it prints "Hello".
How expansion is working?

Correctly. Stringizing doesn't just slap quotes around the value of the
argument, it escapes any metacharacters, too. So pstr("Hello\n")
expands to printf("\"Hello\\n\"").