Question

I use only C99, and, yesterday, I heard that it was impossible to mix several declarations and initializations in ANSI C. Thus, codes like this :

unsigned x = 42, y = 21;
double e = 3.14;

Would be, with gcc’ -pedantic flag :

unsigned x, y;
double e;

x = 42, y = 21;
e = 3.14;

I’m surprised, because I didn’t find any information about that in C89 draft, and a code like this works fine…

unsigned x = 42, y = 21;
double e = 3.14;

Sorry, it seems to be a trivial question, but I did some research, and nothing told me about this rule…
Is it true ?

Answer 1

An initialization is a part of declaration, so you can do initialization in a declaration in both C89/C99:

/* Valid in C89 and C99. There are no statement, only declarations */
unsigned x = 42, y = 21;
double e = 3.14;

What you cannot do is to mix statements and declarations in C89:

/* Not valid in C89, valid in C99: mixing declarations and statements */
unsigned x, y;
x = 42, y = 21;

double e;
e = 3.14;