asked on

static variables

This question might have to do with some knowledge of AIX4.2.x based C++ compiler(xlC_r). I am new to this environment. here it goes:

i've a C++ class file with a certain static variable(say "astat". this goes into a shared library and this library is linked into an executable.
now when I run this executable(the file that intializes/defines this static var is part of only the shared library), i find 2 addresses for the static varible "astat" when accessed from 2 different functions. why would this happen ??

if you are familiar with AIX's makeC++SharedLib_r/xlC_r to create shared libs and executables respectively, is there a link line option to supress these multiple copies ?

mlev

The definition/initialization isn't in a header file, right?

rajaram

ASKER

here it goes:

file: hdr.h
-----

class A {
private:
static sp var1; // sp - a struct definition.
public:
..
..
stativ void initVars();
static void someOperation();
..
..
};
________________________________________________________________

file impl.cpp
--------

sp A::var1;

void A::initVars() {
// initialize the static varible
};

void A::someOperation() {
// this function is accessed by various routines to
// use/manipulate the stativ var
};

.
.
____________________________________________________________

xyu

Did You tell to the compiler & linker that class A is expoted/imported any way ???

xyu

I see additional problem in Your code ... You have to specify initializer to You static variable... nobody garanted order of initialization of statics

rajaram

ASKER

1st comment :
i have not used any options which will tell the compiler/linker to export/import these files. frankly i dont know if I have to
do it or how to export/import files ?

2nd comment:

please see the .cpp file. the first line (sp A::var1;) should
do. atleast this works on SOLARIS/HPUX/WIN-NT.
do i've to equate it to NULL or something ??

xyu

2 nd comment... its good practice to specify initializer (constructor) for static variable (by stabdard it have to be zerroed, but i'v seen alredy 2 cases where it wasn't 0) :)

look at documentation on Your compiler for keywords export/import, _export/_import ... it may help You... I don't have compiler here so i can't check it ... but export/import is standard keyword... so check it.. and shoe me the results if any... i'll help You then

rajaram

ASKER

i'll hunting for the compiler/linker documentation. once i get
them i'll try and let you know.
thanks.

xyu

the suggestion is the next try to do like that

in hdr.h

#ifndef HDR_DECLSPEC
#define HDR_DECLSPEC _export
#endif

class HDR_DECLSPEC A {
private:
static sp var1; // sp - a struct definition.
public:
..
..
stativ void initVars();
static void someOperation();
..
..
};

and before using in in the main (non-shared part of the program)
do
#define HDR_DECLSPEC _import

it may help

rajaram

ASKER

WHEN does one require to export/import files ?
btw, this is an encouraging suggestion. thanks!

Coming from a SOLARIS background, i've never understood the
logic/reason behind export/import of files(if possible please
answer the "WHEN" part).

great suggestion!!

ASKER CERTIFIED SOLUTION

xyu

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