Hi,
I have the following program:
#include <stdarg.h>
class A {
public:
A() { }
}
void f(A a,...) {
va_list l;
va_start(l,a);
// ...
va_end(l);
}
When I try to compile this program (using gcc), the compiler moans
about the non-POD type in the call to va_start() and threatens to abort
at runtime. Having checked the C-spec, this seems reasonable. What I'm
looking for is some kind of work-around. Is there any way I can get
this work (preferably without changing f() to take an A* argument)? Any
suggestions would be greatly appreciated (even using macroes).
Thanks in advance,
Ross 5 2795
Ross wrote:
Hi,
I have the following program:
#include <stdarg.h>
class A {
public:
A() { }
}
void f(A a,...) {
va_list l;
va_start(l,a);
// ...
va_end(l);
}
When I try to compile this program (using gcc), the compiler moans
about the non-POD type in the call to va_start() and threatens to abort
at runtime. Having checked the C-spec, this seems reasonable.
It does? There are no other types than POD in C. Or did you mean the C++
spec?
What I'm looking for is some kind of work-around. Is there any way I can
get this work (preferably without changing f() to take an A* argument)?
Any suggestions would be greatly appreciated (even using macroes).
Well, variable argument lists cannot be used with non-POD types. I don't
think there is a workaround to get it do what you want.
Rolf Magnus wrote:
Ross wrote:
Hi,
I have the following program:
#include <stdarg.h>
class A {
public:
A() { }
}
void f(A a,...) {
va_list l;
va_start(l,a);
// ...
va_end(l);
}
When I try to compile this program (using gcc), the compiler moans
about the non-POD type in the call to va_start() and threatens to abort
at runtime. Having checked the C-spec, this seems reasonable.
It does? There are no other types than POD in C. Or did you mean the C++
spec?
Yes, I meant the C++ spec. Sorry about the typo.
void f(A a, int nDummy,...) {
You can use a dummy integer as the identifier of the rightmost named
parameter. Pass this nDummy to the va_start macro. I think this should
work. (Also the non-PODs should not be passed as a variable argument to
this function.)
Amir Kamerkar
Rolf Magnus wrote:
Ross wrote:
>Hi,
I have the following program:
#include <stdarg.h>
class A { public: A() { } }
void f(A a,...) { va_list l; va_start(l,a); // ... va_end(l); }
...
>What I'm looking for is some kind of work-around. Is there any way I can get this work (preferably without changing f() to take an A* argument)? Any suggestions would be greatly appreciated (even using macroes).
Well, variable argument lists cannot be used with non-POD types. I don't
think there is a workaround to get it do what you want.
Well, the "non-POD" restriction does indeed apply to the arguments that
are passed as _variable_ ones (i.e. correspond to the '...' portion of
parameter declaration list), but I don't see anything in the standard
that would also extend this requirement to the explicitly declared
parameters, including the one used in 'va_start'. Am I missing something?
--
Best regards,
Andrey Tarasevich
Andrey Tarasevich wrote:
Rolf Magnus wrote:
Ross wrote:
Hi,
I have the following program:
#include <stdarg.h>
class A {
public:
A() { }
}
void f(A a,...) {
va_list l;
va_start(l,a);
// ...
va_end(l);
}
...
What I'm looking for is some kind of work-around. Is there any way I can
get this work (preferably without changing f() to take an A* argument)?
Any suggestions would be greatly appreciated (even using macroes).
Well, variable argument lists cannot be used with non-POD types. I don't
think there is a workaround to get it do what you want.
Well, the "non-POD" restriction does indeed apply to the arguments that
are passed as _variable_ ones (i.e. correspond to the '...' portion of
parameter declaration list), but I don't see anything in the standard
that would also extend this requirement to the explicitly declared
parameters, including the one used in 'va_start'. Am I missing something?
As I understood it, the argument passed to va_start() should have the
type that results if you were to pass an argument of that type to an
ellipsis. Therefore, it can't be a non-POD type because it's undefined
to pass a non-POD type to an ellipsis. I don't have my copy of the spec
to hand, though, so I could be wrong.
Ross This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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