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Stack Operations (Package V_Stack)

This chapter contains an overview describing this package. This overview section is followed by a detailed description of each subprogram in this package.

The following topics are covered in this section:


Package Overview

Description

The package V_Stack provides stack operations. The procedure Check_Stack returns the current value of the stack pointer and the lower limit of the stack. Another procedure is provided to extend the current stack.

Package Procedures And Functions

Table 24 lists the procedures and functions in package V_Stack with a brief description of each subprogram.

Table 24 Procedures and Functions
Name
Description
procedure Check_Stack
Returns the current value of the stack pointer and the lower limit of the stack.
procedure Extend_Stack
Extends the current stack.

Package Specification


Procedures and Functions in Package V_Stack

procedure Check_Stack

Syntax

Arguments

Description

Check_Stack returns the current value of the stack pointer and the stack lower bound. This information is used to determine the amount of space remaining on the stack. The current out parameter returned by Check_Stack is a close approximation of the current SP. Because of compiler code, Check_Stack may return a value that is a few bytes lower than the actual SP.

Under certain conditions, code generated by this procedure cannot use the stack. However, the compiler can implicitly generate code that uses the stack to generate a reference to the parameters. Disassembly of the inline expansion can be used to determine if a given call performs stack allocation.

procedure Extend_Stack

Syntax

Description

This service is not supported. It always raises Storage_Error exception.


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