C
Christopher M. Lusardi
Hello,
How is this possible. If I have two separate files that include the
same dot h file as described below why am I allowed to access the same
value for a constant. I compiled this program using a makefile. (Sorry,
I can't post the long makefile or program.)
What the code is suppose to do is: main () includes the file and the
variable multible_defined_var actually gets defined. file2.c will get the
external definition only because now the constant TESTC is defined.
If I fool around with the makefile I can remove the error saying variable
multible_defined_var is multiply defined and the program works fine.
The reason I have to know is if I create another test program and define
just a constant without any other pre-compiler directives involved in just
main() it's undefined in other program files.
file1.c
-------
#include "test.h"
main ()
{
....
t2 ();
}
test.h
------
#ifndef TESTC
#define TESTC
int multible_defined_var;
#else
extern int multible_defined_var;
#endif
file2.c
-------
#include "test.h"
void t2 ()
{
....
}
Thank you,
Christopher Lusardi
P.S.: I apologize if there is a typo in the code I posted.
How is this possible. If I have two separate files that include the
same dot h file as described below why am I allowed to access the same
value for a constant. I compiled this program using a makefile. (Sorry,
I can't post the long makefile or program.)
What the code is suppose to do is: main () includes the file and the
variable multible_defined_var actually gets defined. file2.c will get the
external definition only because now the constant TESTC is defined.
If I fool around with the makefile I can remove the error saying variable
multible_defined_var is multiply defined and the program works fine.
The reason I have to know is if I create another test program and define
just a constant without any other pre-compiler directives involved in just
main() it's undefined in other program files.
file1.c
-------
#include "test.h"
main ()
{
....
t2 ();
}
test.h
------
#ifndef TESTC
#define TESTC
int multible_defined_var;
#else
extern int multible_defined_var;
#endif
file2.c
-------
#include "test.h"
void t2 ()
{
....
}
Thank you,
Christopher Lusardi
P.S.: I apologize if there is a typo in the code I posted.