Revision [22370]
This is an old revision of KeyPgOpNew made by fxm on 2018-08-25 07:59:43.
Operator New
Operator to dynamically allocate memory and construct data of a specified type.
Syntax:
declare operator new ( size as uinteger ) as any ptr
declare operator new[] ( size as uinteger ) as any ptr
declare operator new[] ( size as uinteger ) as any ptr
Usage:
result = New datatype
or
result = New datatype ( initializers, ... )
or
result = New datatype[ count ]Parameters:
size
Number of bytes to allocate.
initializers
Initial value(s) for the variable.
datatype
Name of the data type to create.
count
Exact number of elements to allocate.
Return Value:
A pointer of type datatype to the newly allocated data.
Description:
The New operator dynamically allocates memory and constructs a specified data type.
For simple types, like integers, an initial value can be given. For types without constructors, initial values can be specified for each field (either with default initializer at data-field declaration, or with initializer list as in New datatype (initializers, ..) if all type data-fields are numeric primitives only and without any default initializers). For types with at least one constructor, the initialize list (if any) must match an existing constructor. If no initializers are given, the default values for those types will be set.
New[] is the array-version of the New operator and allocates enough memory for the specified number of objects. The default constructor for the type will be used to set the initial values for each item.
Objects created with New must be freed with Delete. Memory allocated with New[] must be freed with Delete[], the array-version of Delete. You cannot mix and match the different versions of the operators.
Specifying an initial value of Any, as in New datatype (Any) will allocate memory for the type, but not initialize the data. This is only valid on data types that do not have constructors (otherwise for data types with constructors, syntax of simple memory allocation with pointer conversion, like Cptr(datatype Ptr, Allocate(Sizeof(datatype))), can be substituted to the invalid use of New...Any).
Specifying an initial value of Any, as in New datatype[count] {Any} will allocate memory for the array, but not initialize the data. This is only valid on data types that do not have constructors (otherwise for data types with constructors, syntax of simple memory allocation with pointer conversion, like Cptr(datatype Ptr, Allocate(count * Sizeof(datatype))), can be substituted to the invalid use of New...Any).
This operator can be overloaded for user-defined types as a member Operator.
Note: Using pointer = New datatype[count] may be unsafe if pointer was declared with a type different from datatype (for sub-type polymorphism purpose for example), because the pointer arithmetic fails to access the elements if the pointer type size is different from the size of datatype (when using Operator [] (Pointer index) or adding an offset (element number) to the pointer, or even when Delete[] itself (the array-version of Delete) must destroy the elements).
For simple types, like integers, an initial value can be given. For types without constructors, initial values can be specified for each field (either with default initializer at data-field declaration, or with initializer list as in New datatype (initializers, ..) if all type data-fields are numeric primitives only and without any default initializers). For types with at least one constructor, the initialize list (if any) must match an existing constructor. If no initializers are given, the default values for those types will be set.
New[] is the array-version of the New operator and allocates enough memory for the specified number of objects. The default constructor for the type will be used to set the initial values for each item.
Objects created with New must be freed with Delete. Memory allocated with New[] must be freed with Delete[], the array-version of Delete. You cannot mix and match the different versions of the operators.
Specifying an initial value of Any, as in New datatype (Any) will allocate memory for the type, but not initialize the data. This is only valid on data types that do not have constructors (otherwise for data types with constructors, syntax of simple memory allocation with pointer conversion, like Cptr(datatype Ptr, Allocate(Sizeof(datatype))), can be substituted to the invalid use of New...Any).
Specifying an initial value of Any, as in New datatype[count] {Any} will allocate memory for the array, but not initialize the data. This is only valid on data types that do not have constructors (otherwise for data types with constructors, syntax of simple memory allocation with pointer conversion, like Cptr(datatype Ptr, Allocate(count * Sizeof(datatype))), can be substituted to the invalid use of New...Any).
This operator can be overloaded for user-defined types as a member Operator.
Note: Using pointer = New datatype[count] may be unsafe if pointer was declared with a type different from datatype (for sub-type polymorphism purpose for example), because the pointer arithmetic fails to access the elements if the pointer type size is different from the size of datatype (when using Operator [] (Pointer index) or adding an offset (element number) to the pointer, or even when Delete[] itself (the array-version of Delete) must destroy the elements).
Examples:
Type Rational
As Integer numerator, denominator
End Type
Scope
' Create and initialize a "rational" and store its address.
Dim p As Rational Ptr = New Rational(3, 4)
Print p->numerator & "/" & p->denominator
' Destroy the rational and give its memory back to the system.
Delete p
End Scope
Scope
' Allocate memory for 100 integers and store the address of the first one.
Dim p As Integer Ptr = New Integer[100]
' Assign some values to the integers in the array.
For i As Integer = 0 To 99
p[i] = i
Next
' Free the entire integer array.
Delete[] p
End Scope
As Integer numerator, denominator
End Type
Scope
' Create and initialize a "rational" and store its address.
Dim p As Rational Ptr = New Rational(3, 4)
Print p->numerator & "/" & p->denominator
' Destroy the rational and give its memory back to the system.
Delete p
End Scope
Scope
' Allocate memory for 100 integers and store the address of the first one.
Dim p As Integer Ptr = New Integer[100]
' Assign some values to the integers in the array.
For i As Integer = 0 To 99
p[i] = i
Next
' Free the entire integer array.
Delete[] p
End Scope
Dialect Differences:
- Only available in the -lang fb dialect.
Differences from QB:
- New to FreeBASIC
See also:
Back to Memory Operators
Back to Operators
