* Should this compile and link??
@ 2002-01-16 12:34 Bill Priest
2002-01-16 14:28 ` Ross Boylan
0 siblings, 1 reply; 2+ messages in thread
From: Bill Priest @ 2002-01-16 12:34 UTC (permalink / raw)
To: gcc-help
c4e3.cc
---------------
#include "c4e3.h"
int main(void)
{
TEST_TYPE test1;
test1.f1();
}
----------------
c4e3_func.cc
----------------
#include <cstdio>
#include "c4e3.h"
void TEST_TYPE::f1(void)
{
puts("c4e3");
}
------------------
c4e3.h
------------------
#ifndef C4E3_H
#define C4E3_H
typedef struct // TEST_TYPE
{
void f1(void);
} TEST_TYPE;
#endif
--------------------
w/ stock g++ 3.0.3 the following commands
g++ -c -o c4e3.o c4e3.cc
g++ -c -o c4e3_func.o c4e3_func.cc
g++ c4e3.o c4e3_func.o -o c4e3
c4e3.o: In function `main':
c4e3.o(.text+0x11): undefined reference to `TEST_TYPE::f1()'
If I uncomment TEST_TYPE in c4e3 everything compiles and links
as it should.
If I change c4e3.cc to include "c4e3_func.cc" and change the command to
g++ -o c4e3 c4e3.cc
then it compiles and links even if the c4e3.h file is unchanged (ie TEST_TYPE is commented out).
This doesn't make a whole lot of sense to me; but I'm not a C++ expert or even novice.
Neither of my books (Thinking in C++ and C++ for C programmers) seems to cover this explicitly.
Is there something I'm missing here. Scoping or namespace resolution was the only thing I could
come up with but didn't see anything in either of the books.
Please set me straight,
Bill
_________________________________________________________
Do You Yahoo!?
Get your free @yahoo.com address at http://mail.yahoo.com
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Should this compile and link??
2002-01-16 12:34 Should this compile and link?? Bill Priest
@ 2002-01-16 14:28 ` Ross Boylan
0 siblings, 0 replies; 2+ messages in thread
From: Ross Boylan @ 2002-01-16 14:28 UTC (permalink / raw)
To: Bill Priest; +Cc: gcc-help, Ross Boylan
In your example, you have created an anonymous structure, and then
created a typedef for it.
Since it is anonymous, there is no way to refer to it, and thus your
definition of f1 doesn't get associated properly. I'm a little
suprised the compiler doesn't give you an error in c4e3_func.cc when
you refer to the class or structure TEST_TYPE.
Consider this to clarify things:
struct SILLY {
void f1(void);
};
typedef SILLY TEST_TYPE;
If you want to define f1, you must say
SILLY::f1
not TEST_TYPE::f1.
However, in your example there is no name SILLY, so no way to refer to
the function.
Alternately, you could
typedef struct {
void f1(void) (puts("something");};
} TEST_TYPE;
and then you'd probably be OK.
I haven't communed with the standards statement, but I think this is
what's going on.
On Wed, Jan 16, 2002 at 02:27:29PM -0600, Bill Priest wrote:
> c4e3.cc
> ---------------
> #include "c4e3.h"
>
> int main(void)
> {
> TEST_TYPE test1;
>
> test1.f1();
> }
> ----------------
> c4e3_func.cc
> ----------------
> #include <cstdio>
> #include "c4e3.h"
>
> void TEST_TYPE::f1(void)
> {
> puts("c4e3");
> }
> ------------------
>
> c4e3.h
> ------------------
> #ifndef C4E3_H
> #define C4E3_H
>
> typedef struct // TEST_TYPE
> {
> void f1(void);
> } TEST_TYPE;
>
> #endif
> --------------------
>
> w/ stock g++ 3.0.3 the following commands
>
> g++ -c -o c4e3.o c4e3.cc
> g++ -c -o c4e3_func.o c4e3_func.cc
> g++ c4e3.o c4e3_func.o -o c4e3
> c4e3.o: In function `main':
> c4e3.o(.text+0x11): undefined reference to `TEST_TYPE::f1()'
>
> If I uncomment TEST_TYPE in c4e3 everything compiles and links
> as it should.
>
> If I change c4e3.cc to include "c4e3_func.cc" and change the command to
> g++ -o c4e3 c4e3.cc
> then it compiles and links even if the c4e3.h file is unchanged (ie TEST_TYPE is commented out).
>
> This doesn't make a whole lot of sense to me; but I'm not a C++ expert or even novice.
> Neither of my books (Thinking in C++ and C++ for C programmers) seems to cover this explicitly.
>
> Is there something I'm missing here. Scoping or namespace resolution was the only thing I could
> come up with but didn't see anything in either of the books.
>
> Please set me straight,
>
> Bill
>
> _________________________________________________________
> Do You Yahoo!?
> Get your free @yahoo.com address at http://mail.yahoo.com
>
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2002-01-16 22:28 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2002-01-16 12:34 Should this compile and link?? Bill Priest
2002-01-16 14:28 ` Ross Boylan
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).