Static variable initalization

[mrsinger]

I have a multi-threaded application (non posix) that needs to put a
semaphore around the constructor/destructor of a class. So, I have a
static variable which is the semaphore. Now, I have to make an OS call
to init the variable before any constructor for the class is called.
The code below give me a link error:

unresolved external symbol "private: static int test::sem"

I've been searching through old posts, but can't find anything anything
close. What is the correct way to do this?

---------------------
void OS_CreateSem(in t *sem)
{
*sem = 1;
}

class test
{
private:
static int sem;

public:
static void makesem()
{
OS_CreateSem(&s em);
}

test()
{
//take semaphore
//do construction stuff
//release semaphore
}
};

void main()
{
test::makesem() ;
class test()
}

[Victor Bazarov]

mr******@usa.ne t wrote:

I have a multi-threaded application (non posix) that needs to put a
semaphore around the constructor/destructor of a class. So, I have a
static variable which is the semaphore. Now, I have to make an OS
call to init the variable before any constructor for the class is
called. The code below give me a link error:

unresolved external symbol "private: static int test::sem"

I've been searching through old posts, but can't find anything
anything close. What is the correct way to do this?

---------------------
void OS_CreateSem(in t *sem)
{
*sem = 1;
}

class test
{
private:
static int sem;

You declared it here. Where is it defined?

>
public:
static void makesem()
{
OS_CreateSem(&s em);
}

test()
{
//take semaphore
//do construction stuff
//release semaphore
}
};

void main()

There is no 'void main' in C++.

{
test::makesem() ;
class test()
}

V
--
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I do not respond to top-posted replies, please don't ask

[Joseph Paterson]

mr******@usa.ne t wrote:

I have a multi-threaded application (non posix) that needs to put a
semaphore around the constructor/destructor of a class. So, I have a
static variable which is the semaphore. Now, I have to make an OS call
to init the variable before any constructor for the class is called.
The code below give me a link error:

unresolved external symbol "private: static int test::sem"

I've been searching through old posts, but can't find anything anything
close. What is the correct way to do this?

---------------------
void OS_CreateSem(in t *sem)
{
*sem = 1;
}

class test
{
private:
static int sem;

public:
static void makesem()
{
OS_CreateSem(&s em);
}

test()
{
//take semaphore
//do construction stuff
//release semaphore
}
};

void main()
{
test::makesem() ;
class test()
}

You need a

int test::sem = 0;

in there somewhere.

When you add the static keyword to a member variable, it doesn't
actually allocate memory for it, it just declares it's existence. By
adding the line above, you allocate memory for it.
Don't include that line in a header file, as it should only appear
once.

Joseph.

[Salt_Peter]

mr******@usa.ne t wrote:

I have a multi-threaded application (non posix) that needs to put a
semaphore around the constructor/destructor of a class. So, I have a
static variable which is the semaphore. Now, I have to make an OS call
to init the variable before any constructor for the class is called.
The code below give me a link error:

unresolved external symbol "private: static int test::sem"

Read the pertinent sections about defining static member variables in:
http://www.parashift.com/c++-faq-lite/ctors.html

>
I've been searching through old posts, but can't find anything anything
close. What is the correct way to do this?

---------------------
void OS_CreateSem(in t *sem)
{
*sem = 1;
}

class test
{
private:
static int sem;

public:
static void makesem()
{
OS_CreateSem(&s em);
}

test()
{
//take semaphore
//do construction stuff
//release semaphore
}
};

void main()
{
test::makesem() ;
class test()
}