Pointer
- Dart course
- Expert
- Lesson 17/47
- 5 min
Learn memory management with Pointer.
Pointer
Pointer is the dart:ffi type that represents C-side memory addresses. Pointer<Int32> represents an integer address, Pointer<Double> a floating-point address, and Pointer<Void> an untyped address.
Pointers are read/written via the value property: ptr.value = 42; or ptr.value. To allocate memory, use calloc<Int32>() or malloc<Int32>(). Pointers are not managed by Dart's garbage collector; manual deallocation is required.
Memory management
Pointer memory is not managed by Dart's garbage collector; manual management is required. calloc allocates zeroed memory, malloc unzeroed. Allocated memory is freed with ptr.callocFree() or ptr.free().
Incorrect management causes leaks or double frees. The using or arena patterns automatically free memory. Pointer arithmetic is done with ptr + 1 or ptr.elementAt(n).
Practice A PointerInfo class
Define a PointerInfo class with final String type; final int address; PointerInfo(this.type, this.address); field and constructor. Add a String describe() => 'Pointer<$type> @ $address'; method. In main create final pi = PointerInfo('Int32', 0);; print with print(pi.describe());.
Starter code
void main() {
// define a PointerInfo class (type, address; describe)
// create a PointerInfo; print describe()
}Sample solution
class PointerInfo {
final String type;
final int address;
PointerInfo(this.type, this.address);
String describe() => 'Pointer<$type> @ $address';
}
void main() {
final pi = PointerInfo('Int32', 0);
print(pi.describe());
}Expected output
Pointer<Int32> @ 0
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 A Pointer type
final ptr = Pointer<____>.fromAddress(0);final ptr = Pointer<Int32>.fromAddress(0);Explanation: Pointer<Int32> is an integer memory address.
2 Match the Pointer operations
| Term | Meaning |
|---|---|
Pointer<Int32> |
Integer address |
ptr.value |
Read/write value |
calloc<T>() |
Zeroed allocation |
ptr.free() |
Deallocation |
3 What manages pointer memory?
- Dart garbage collector
- Manual management Correct answer
- Automatically by browser
- By the OS automatically
Explanation: pointer memory is managed manually (calloc/malloc + free).