Help with C++ compile error

[Mark]

Hi,

We have a class that defines an exception:

template <class A, class B, class C, class D > class X : public Y
{
...
class SomeException : public BaseException
{
...
}
};

We need to catch the exception in another class:

template <class Dispatcher> class Something : public YetAnotherClass
{
Dispatcher *fDispatcher;

void HandleMessage(...)
{
try {
...
} catch (Dispatcher::SomeException) // This line has the error
{
...
}
}
....

[some code omitted for brevity]

This code compiles under Sun Workshop 6 update 2 and under Compaq C++
V6.5-004 for OpenVMS Alpha V7.3-1 but not under GNU C++ V3.3.5 and
2.95.4 (on debian Linux).

The error message is "parse error before ';' token" on the 'catch'
line.

Can anyone tell me if this is a compiler bug or is the syntax
incorrect?

TIA, Mark

 

[Rolf Magnus]

Hi,

We have a class that defines an exception:

template <class A, class B, class C, class D > class X : public Y
{
...
class SomeException : public BaseException
{
...
}
};

We need to catch the exception in another class:

template <class Dispatcher> class Something : public YetAnotherClass
{
Dispatcher *fDispatcher;

void HandleMessage(...)
{
try {
...
} catch (Dispatcher::SomeException) // This line has the error

} catch (typename Dispatcher::SomeException)

{
...
}
}
...

[some code omitted for brevity]

This code compiles under Sun Workshop 6 update 2 and under Compaq C++
V6.5-004 for OpenVMS Alpha V7.3-1 but not under GNU C++ V3.3.5 and
2.95.4 (on debian Linux).

The error message is "parse error before ';' token" on the 'catch'
line.

Can anyone tell me if this is a compiler bug or is the syntax
incorrect?

I think the syntax is correct, but not the semanctics. SomeException is a
name dependand on a template argument. In such a situation, you have to
explicitly tell the compiler that it's a type, otherwise it is required to
assume that it's a value.

 

[Greg]

Hi,

We have a class that defines an exception:

template <class A, class B, class C, class D > class X : public Y
{
...
class SomeException : public BaseException
{
...
}
};

We need to catch the exception in another class:

template <class Dispatcher> class Something : public YetAnotherClass
{
Dispatcher *fDispatcher;

void HandleMessage(...)
{
try {
...
} catch (Dispatcher::SomeException) // This line has the error
{
...
}
}
...

[some code omitted for brevity]

This code compiles under Sun Workshop 6 update 2 and under Compaq C++
V6.5-004 for OpenVMS Alpha V7.3-1 but not under GNU C++ V3.3.5 and
2.95.4 (on debian Linux).

The error message is "parse error before ';' token" on the 'catch'
line.

The error is probably a missing "typename" keyword. I would change the
catch line to read:

catch (typename Dispatcher::SomeException)

Greg

 

[Mark]

The error is probably a missing "typename" keyword. I would change the
catch line to read:

catch (typename Dispatcher::SomeException)

Thanks Rolf and Greg, that has solved it

Mark