getting return value from function without return statement.

[Seong-Kook Shin]

Hi.

Just curiocity,

Because of pre-ANSI C, it is possible to have a function without specifying
return type of a function (which makes the return type 'int', though) and
give no 'return' statement. For example:

foo(int a, int b)
{
int sum;
sum = a + b;
}

void
bar(void)
{
int i = foo(1, 2);
...
}

In above code, the 'i' variable in bar() will have no useful value.
But what does the standard says? I overlooked the ISO C standard, but
found no mention about this problem.

Is this a kind of 'undefined bebavior'? Or 'unspecified behavior'?

If there's wrong point on my explanation, please enlighten me. ;-)
Or, could you give me the section number of ISO C document where it deals
with such case?

 

[Richard Bos]

foo(int a, int b)
{
int sum;
sum = a + b;
}

void
bar(void)
{
int i = foo(1, 2);
...
}

In above code, the 'i' variable in bar() will have no useful value.
But what does the standard says?

That it invokes undefined behaviour (which is worse than having no
useful value; it could crash, for example):

# 12 If the } that terminates a function is reached, and the value of
# the function call is used by the caller, the behavior is undefined.

That's from 6.9.1.

Richard