Design issue

[Philipp.Weissenbacher]

Hi all!

I've got something of a design issue here:

class Bucket {
public:
// Initial capacity of a bucket (= # of items in a page)
static const unsigned int M = 10;

// Key store
Key keyStore[M];

// Count of items in the bucket
int count;

// Bucket's depth (number of significant bits)
int localDepth;

Bucket();
~Bucket();
};

Now, I use Bucket in a data structure like this:

#include "Bucket.h"

Foobar::Foobar() : a(0), b(0), c(0) {
}

void Foobar buzz() {
if(Bucket::M < 1)
...
}

Although this compiles just fine, if I want to use it e.g. write
something like

#include "Foobar.h"
int maint() {
Foobar* b = new Foobar();
}

I get a "undefined reference" from ld. Googling on this I found out
that I have one has to initialize a static variable in exactly one
compilation unit (see [10.10] Why can't I initialize my static member
data in my constructor's initialization list? by Marshall Cline).
But how do I fix this?

Thanks in advance,
Philipp

 

[Erik Wikström]

Hi all!

I've got something of a design issue here:

class Bucket {
public:
// Initial capacity of a bucket (= # of items in a page)

static const unsigned int M;

// Key store
Key keyStore[M];

// Count of items in the bucket
int count;

// Bucket's depth (number of significant bits)
int localDepth;

Bucket();
~Bucket();
};

In Bucket.cpp add:

Bucket::M = 10;

I get a "undefined reference" from ld. Googling on this I found out
that I have one has to initialize a static variable in exactly one
compilation unit (see [10.10] Why can't I initialize my static member
data in my constructor's initialization list? by Marshall Cline).
But how do I fix this?

The answer can be found in item 10.11 in the same FAQ.

 

[Erik Wikström]

In Bucket.cpp add:

Bucket::M = 10;

Make that 'const unsigned int Bucket::M = 10;'.

 

[Philipp.Weissenbacher]

Make that 'const unsigned int Bucket::M = 10;'.

Thanks a lot guys!