Initialize static array in C++

Question

I have these classes:

class FS{
  static char mount(Partition* p)
      {return myImpl->mount(p);}
  /*...*/
  KernelFS* myImpl;
};

class KernelFS{
char mount(Partition* p){
   /*...*/
   while(available[i]) i++;
}
  /*...*/
  static bool available[26];
};

Main program only uses static functions from FS, e.g:

void main(){
  Partition* p=/*...*/;
  FS::mount(p);
  /*...*/
}

When FS::mount(p) is called, it calls myImpl->mount(p) (which is a function from KernelFS class). And here's the problem. When it comes to

while(available[i]) i++;

...it breaks! I think the problem is that I haven't initialized the array available[26], and I have no idea how to do that... What else can be the problem? Please help.

Btw, main() never creates FS or KernelFS objects, so I think that there is no use of constructors...

KernelFS* myImpl; is declared static, correct?

Sergey Kalinichenko
– Sergey Kalinichenko

2012-01-25 10:09:40 +00:00
Commented Jan 25, 2012 at 10:09 — Sergey Kalinichenko
– Sergey Kalinichenko, Commented Jan 25, 2012 at 10:09
Perhaps initiation order related?

Joseph Quinsey
– Joseph Quinsey

2012-01-25 10:10:28 +00:00
Commented Jan 25, 2012 at 10:10 — Joseph Quinsey
– Joseph Quinsey, Commented Jan 25, 2012 at 10:10
this as already been addressed in another question

João Portela
– João Portela

2012-01-25 10:15:33 +00:00
Commented Jan 25, 2012 at 10:15 — João Portela
– João Portela, Commented Jan 25, 2012 at 10:15

Alok Save · Accepted Answer · 2012-01-25 10:07:28Z

10

You need to define it in (exactly)one of your cpp files:

bool KernelFS::available[] = {0};

answered Jan 25, 2012 at 10:07

Alok Save

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7 Comments

Ulterior Over a year ago

always looked ugly, but thats it

zdd Over a year ago

What if the initial values are not same? Can I use a loop?

Alok Save Over a year ago

@zdd: Well it will be really intuitive but if you really want to get it towork, here is an implementation.

zdd Over a year ago

@Alok Save, I look at the code again, it's not an static array, even not a array in a class, can you double check it?

Alok Save Over a year ago

@zdd: I understood what your requirement is when you posted your first comment. What I said in my previous comment is the code example I showed can be easily modified to make array a static class member. Here i did it for you.

|

Adam Zalcman · Accepted Answer · 2012-01-25 10:44:27Z

5

The problem is that the array is never allocated any memory. You should add this in the global scope:

bool KernelFS::available[] = {false};

Make sure you do it in one cpp file. Adding it in more than one cpp file will result in duplicate symbol error during linking. Also, you shouldn't do this in a header file. The best approach is to add this in the cpp file with the implementation of the KernelFS class.

Note also that static initialization order across compilation units isn't guaranteed. Hence you shouldn't call KernelFS::mount() from static initialization code in another file.

edited Jan 25, 2012 at 10:44

answered Jan 25, 2012 at 10:08

Adam Zalcman

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