Boost compile error when a object of type pool is contained in another class

[mackenzie]

Hello,
I am looking for a little bit of help. I am trying to create a
dynamically allocated object which contains one or more objects of
type boost:ool<>. I get a compiler error when an object of this type
is contained in my class and am not sure why. To be honest I have a
little but not a lot of experience with templates and it could simply
be obvious to a more experienced template user; however, the answer
escapes me.

Here is a sample code snippet:

#include <boost/pool/pool.hpp>
#include <boost/pool/singleton_pool.hpp>

struct Foobar
{
boost:ool<> p(sizeof(int)); // this is line 182

};

boost:ool<> yp(512);

int main()
{
Foobar foobar;

printf( "%u\n", sizeof( boost:ool<>(512) ) );

return( 0 );
}

----------------------
Here is the error message:
ramMgr.cxx:182: error: expected identifier before #sizeof#
ramMgr.cxx:182: error: expected #,# or #...# before #sizeof#
---------------------------
compiler & version
g++ -v
gcc version 4.1.1 20060724 (4.1.1-3mdk)


Thanks,
Parker

 

[Victor Bazarov]

Hello,
I am looking for a little bit of help. I am trying to create a
dynamically allocated object which contains one or more objects of
type boost:ool<>. I get a compiler error when an object of this type
is contained in my class and am not sure why. To be honest I have a
little but not a lot of experience with templates and it could simply
be obvious to a more experienced template user; however, the answer
escapes me.

Here is a sample code snippet:

#include <boost/pool/pool.hpp>
#include <boost/pool/singleton_pool.hpp>

struct Foobar
{
boost:ool<> p(sizeof(int)); // this is line 182

What's the 'sizeof' for? Are you trying to initialise it? If so,
initialisation of members belongs to constructor initialiser list.
If you were trying to declare an array, then replace parentheses
with brackets. Most likely you just need to lose the parentheses
and the expression inside them.

};

boost:ool<> yp(512);

int main()
{
Foobar foobar;

printf( "%u\n", sizeof( boost:ool<>(512) ) );

return( 0 );
}

----------------------
Here is the error message:
ramMgr.cxx:182: error: expected identifier before #sizeof#
ramMgr.cxx:182: error: expected #,# or #...# before #sizeof#
---------------------------
compiler & version
g++ -v
gcc version 4.1.1 20060724 (4.1.1-3mdk)


Thanks,
Parker

V

 

[mackenzie]

What's the 'sizeof' for? Are you trying to initialise it? If so,
initialisation of members belongs to constructor initialiser list.
If you were trying to declare an array, then replace parentheses
with brackets. Most likely you just need to lose the parentheses
and the expression inside them.












V

Thanks for responding.

What I thought I was doing was creating a member of Foobar named p of
type boost:ool<> which takes a size_type as an argument to the
constructor. It seems to work in the global name space; however, when
I put it into a structure or class I get the error.

From : http://www.boost.org/libs/pool/doc/interfaces/pool.html

template <typename UserAllocator = default_user_allocator_new_delete>
class pool
{...
explicit pool(size_type requested_size);
};

Perhaps after the drive home and a clearer head I will stare at it
some more with your suggestion in mind and the answer will be a little
more obvious.

Thanks,
Parker

 

[Victor Bazarov]

Hello,
I am looking for a little bit of help. I am trying to create a
dynamically allocated object which contains one or more objects of
type boost:ool<>. I get a compiler error when an object of this
type is contained in my class and am not sure why. To be honest I
have a little but not a lot of experience with templates and it
could simply be obvious to a more experienced template user;
however, the answer escapes me.

Here is a sample code snippet:

#include <boost/pool/pool.hpp>
#include <boost/pool/singleton_pool.hpp>

struct Foobar
{
boost:ool<> p(sizeof(int)); // this is line 182

What's the 'sizeof' for? Are you trying to initialise it? If so,
initialisation of members belongs to constructor initialiser list.
If you were trying to declare an array, then replace parentheses
with brackets. Most likely you just need to lose the parentheses
and the expression inside them.
[..]

What I thought I was doing was creating a member of Foobar named p of
type boost:ool<> which takes a size_type as an argument to the
constructor.

You're trying to provide a particular argument in a declaration.
That's not how you initialise the member. Please read about
constructors (of classes) and the _member_initialiser_lists_.

 

[mackenzie]

Thank you Victor.

That makes perfect sense. I was looking at it as if it was being
passed in as a template argument. When in fact it is similar to any
other class.

Thanks again,
Parker

 

[mackenzie]

Thank you Victor.

That makes perfect sense. I was looking at it as if it was being
passed in as a template argument. When in fact it is similar to any
other class.

Thanks again,
Parker

For completeness, in case someone else has a similar question in the
future, the following is the corrected code:

struct Foobar
{
boost:ool<> p; // this was line 182

Foobar() : p( 5 ) {}
};

Reference: 10.4.6.1 Necessary Member Initialization; The C++
Programming Language; Bjarne Stroustrup; May 2004

Thanks again Victor.