Assigning Structure object's variable outside main() gives parse error

thelink123 · 09-02-2010, 08:17 AM

Hi,

Kindly take a look at the code below :

Code:

#include <stdio.h>

struct test
{
   int i;
   int j;
}obj;


obj.i = 5;
obj.j = 10;


int main()
{

   return 0;
}

I am getting the error :

Code:

error: parse error before '.'

Kindly tell me why i am getting this error. I know the error is occuring because i have assigned values to obj.i and obj.j outside main(). But i want to know why do that result in an error. From my part i have created an object 'obj' of stucture 'test' and assigned values to its variables. Where am i going wrong. Expecting a detailed explanation.

bastl · 09-02-2010, 11:01 AM

Yes, outside of main or function is static memory area (section BSS or similar) so you can not code there or assign something:

Code:

struct
{
   int i=5;   // forbidden
   int j;
} obj;

void f1()   // gone to code segment - works!
{
obj.i = 5;
obj.j = 10;
};

grail · 09-02-2010, 11:17 AM

Quote:

Yes, outside of main or function is static memory area (section BSS or similar) so you can not code there or assign something:

I am interested in this question raised by OP but not sure your answer is 'completely' correct, otherwise how would you create a global variable??

Code:

int i = 7;

main(){

printf("%d",i);
return 0;
}

Not pretty perhaps and I definitely do not like global variables when it can be helped, but this works just fine.

bastl · 09-02-2010, 11:25 AM

I can imagine that int is not handled as object so to get an object like struct do:

Code:

int *i = new int;

i=7;   // same error - forbidden

johnsfine · 09-02-2010, 01:18 PM

Quote:

Originally Posted by thelink123

I know the error is occuring because i have assigned values to obj.i and obj.j outside main().

The problem is that you have execution time assignments that are not in any function. (The function doesn't need to be main).

You can assign values to global variables as part of defining the variables as long you use the correct syntax for setting values as part of the definition.

Code:

#include <stdio.h>

struct test
{
   int i;
   int j;
}obj = { 5, 10 };

As you can see, the correct syntax for setting structure members as part of definition of an instance of the structure is a rather ugly syntax (the association of values to members is by sequence rather than name). But that is the syntax C provides.

Sergei Steshenko · 09-02-2010, 02:03 PM

Quote:

Originally Posted by johnsfine

The problem is that you have execution time assignments that are not in any function. (The function doesn't need to be main).

You can assign values to global variables as part of defining the variables as long you use the correct syntax for setting values as part of the definition.

Code:

#include <stdio.h>

struct test
{
   int i;
   int j;
}obj = { 5, 10 };

As you can see, the correct syntax for setting structure members as part of definition of an instance of the structure is a rather ugly syntax (the association of values to members is by sequence rather than name). But that is the syntax C provides.

C99, actually, provides quite nice syntax to initialize structs and not only - see the standard:

http://www.open-std.org/jtc1/sc22/wg...docs/n1124.pdf

, examples on page 76, page 130.

...

To the OP - you should have started from reading the above standard - it doesn't allow the code you published in the opening post.

JohnGraham · 09-03-2010, 03:27 AM

Quote:

Originally Posted by Sergei Steshenko

To the OP - you should have started from reading the above standard

Erm... I'd say that would be a bit over the top. Learning the language by reading the standard cover-to-cover (or even in sections as relevant) would be a waste of time and effort!

Sergei Steshenko · 09-03-2010, 06:41 AM

Quote:

Originally Posted by JohnGraham

Erm... I'd say that would be a bit over the top. Learning the language by reading the standard cover-to-cover (or even in sections as relevant) would be a waste of time and effort!

Just the opposite. The standard has a lot of example.

About 30 or years ago I caught myself tending to find answers in Pascal BNF diagram rather than in the book with it.