The scope of reference, or the scope, of a host variable
is that portion of the program in which the host variable can be accessed.
The placement of the
Informix® ESQL/C declaration
statement determines the scope of the variable as follows:
If the declaration statement is inside a program block, the variable
is local to that program block.
Only statements within
that program block can access the variable.
If the declaration statement is outside a program block, the variable
is modular.
All program blocks that occur after the
declaration can access the variable.
Host variables that you declare within a block of code are local
to that block. You define a block of code with a pair of curly braces,
{ }.
For example, the host variable blk_int in the following
figure is valid only in the block of code between the curly braces,
whereas p_int is valid both inside and outside the block. Figure 1: Declaring host
variables inside and outside a code block
EXEC SQL BEGIN DECLARE SECTION;
int p_int;
EXEC SQL END DECLARE SECTION;
⋮
EXEC SQL select customer_num into :p_int from customer
where lname = "Miller";
⋮
{
EXEC SQL BEGIN DECLARE SECTION;
int blk_int;
EXEC SQL END DECLARE SECTION;
blk_int = p_int;
⋮
EXEC SQL select customer_num into :blk_int from customer
where lname = "Miller";
⋮
}
You can nest blocks up to 16 levels. The global level counts as level one.
The following C rules govern the scope of Informix ESQL/C host variables
as well:
A host variable is an automatic
variable unless you explicitly define it as an external or static variable
or unless it is defined outside of any function.
A host variable that a function declares is local to that function
and masks a definition with the same name outside the function.
You cannot define a host variable more than once in the same block
of code.