"char *" diff in header & func arg list?

"char *" diff in header & func arg list?

[kourama]

I have noticed something that seems wrong to me, and I'd like to know if
anyone can confirm the bug or explain the seemingly strange behaviour.
Attached is a set of files which demonstrates the problem:

http://www.nabble.com/file/7426/a.c a.c 
http://www.nabble.com/file/7427/b.c b.c 
http://www.nabble.com/file/7428/Makefile Makefile 

When the aa function in a.c declares "char *arg" in it's argument list, it
gets a pointer, which means that "char *arg" is equivalent to "char arg[]"
in the argument list.

However, in the file b.c, the declaration "extern char *myarray" is treated
differently from "extern char myarray[]"

It seems to me that, based on the context, the two should be equivalent, but
GCC doesn't treat them that way.

So, is this a bug, legacy behaviour or is this just another wrinkle in the
sharpei puppy that is C?

Many thanks.
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Re: "char *" diff in header & func arg list?

[John Love-Jensen]

Hi kourama,

These two things are mostly interchangeable for most purposes as a
parameter:

char array[];
char* pointer;

On the caller's side, arg1 degenerates into something that almost is the
same as:

char* const arg1;

C proponents would say this is a good thing.  I've been working in C++ long
enough to consider it a bit of a wart (but C++ has far more atrocious warts
than this to worry about), as part of the C legacy.


However, this is an outright mismatch:

extern char array[];
extern char* pointer;

char array[] = "good";
char pointer[] = "bad";

Why?  Because an array of characters is not a pointer to an array of
characters.  The declaration does not match the definition.

> So, is this a bug, legacy behaviour or is this just another wrinkle in the
sharpei puppy that is C?

In this case, not a wrinkle, not a "legacy C" issue.  It is a PEBKAC bug.

HTH,
--Eljay

Re: "char *" diff in header & func arg list?

[kourama]

John Love-Jensen wrote:
> 
> Why?  Because an array of characters is not a pointer to an array of
> characters.  The declaration does not match the definition.
> 

Ah, of course. I was effectly casting the array to a pointer type in the
extern declaration.

Thanks.

Honestly, am I dim or is that a subtle "gotcha"?

eh...don't answer that.
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