Some "safe" languages like Swift and Go offer "unsafe" pointers for use with APIs written in languages like C and Objective-C. Questions using this tag should also have the relevant language tag, e.g. [swift] or [go].
Questions tagged [unsafe-pointers]
250 questions
2
votes
1 answer
Is it legitimate to use LayoutKind.Explicit to get around using "unsafe" pointers?
I have code which does XOR on blocks of data using pointers, which is fast, but I'd like to get rid of the "unsafe" requirement on the assembly. If I change it to use LayoutKind.Explicit and overlay a "ulong[]" on top of a "byte[]", I'm basically…
Bryce Wagner
- 2,640
- 1
- 26
- 43
1
vote
1 answer
Reinterpreting UInt64 as structure
In my code I'm calculating an UInt64 value, then casting it like this:
return *(Cell*)packedUInt64;
Cell is a struct. Marshal.SizeOf(new Cell()) prints 8, so it should match an UInt64, but the cast above crashes with AccessViolationException. I…
Stefan Monov
- 11,332
- 10
- 63
- 120
1
vote
2 answers
Write/read memory using Unsafe in java
I know it is possible to write and read directly to memory by using Unsafe class within the jvm.
Apart from this being really unsafe and somehow counterproductive, I was instead wondering who/what is taking charge of checking the boundaries of the…
Leonardo
- 9,607
- 17
- 49
- 89
1
vote
0 answers
Is this use of unsafe.Pointer OK?
To sum, as helpfully stated by user 9072997:
Since unsafe.Pointer can convert between types that have the same underlying type, can unsafe.Pointer also convert between function types who's arguments & return values have the same underlying type?
I…
nigel239
- 1,485
- 1
- 3
- 23
1
vote
1 answer
Cgo: Write memory in C allocated by Go
For a non-struct slice in Go
a := []byte{0,1,2,3,4,5,6,7}
And pass to C via unsafe.Pointer()
C.some_method((*C.char)(unsafe.Pointer(&a[0])), C.int(len(a)))
Is it safe to write anything into this pointer with caution on it's length?
void…
Wilson Luniz
- 459
- 2
- 7
- 18
1
vote
0 answers
C# working with generic array using unsafe
I need to get a pointer e.g. of type byte* to an array of generic type. I found something
but see pointer to a array of type generic?, nothing that solves my problem. My generic class doesn't have the where T: unmanaged restriction, but internally…
Nullator
- 71
- 2
1
vote
1 answer
How to safely get two mutable pointers to same int?
I would like to create a Rust semaphore wrapping the libc sem_post and sem_wait functions, both of which take a mutable int * parameter. This requires that the waiter and poster simultaneously have a mutable pointer to the same int. How can I…
ridiculous_fish
- 17,273
- 1
- 54
- 61
1
vote
1 answer
Is Microsoft the only one that can write trusted unsafe code?
I would like to write some unsafe C# code for the purpose of writing high-performance, low-level libraries.
But I don't quite understand the limitations of where that code can run.
Microsoft obviously writes libraries that use unsafe code, which are…
Jonathan Wood
- 65,341
- 71
- 269
- 466
1
vote
1 answer
EXC_BAD_ACCESS when trying to pass and read UnsafeMutableRawPointer through VTDecompressionSessionDecodeFrame
I think this is more a pointer question than a VideoToolbox session. I'm trying to do something similar to How to calculate FPS of Hardware Decode on iOS 8 exactly? and pass some metadata through VTDecompressionSessionDecodeFrame's…
LLooggaann
- 425
- 1
- 4
- 16
1
vote
1 answer
'Invalid utf-8 sequence of 1 bytes from index 1' and 'munmup_chunk(): invalid pointer' error in my Rust unit-tests
There`s only lib.rs file:
use libc::{self, O_RDONLY, strerror, open, close, __errno_location, read};
use std::ffi::{CString, CStr};
use std::{fmt, process};
// File descriptor
struct Fd {
fd: i32,
}
impl Fd {
fn new(fd: i32) -> Fd {
…
Michail
- 13
- 4
1
vote
1 answer
Why can I pass [UInt8] type to the UnsafePointer type parameter?
We all know that [UInt8] type is not equal UnsafePointer,
But why can I pass [UInt8] type to UnsafePointer type parameter:
let p = UnsafeMutablePointer.allocate(capacity: 4)
p.initialize(repeating: 0, count: 4)
let ary:[UInt8]…
hopy
- 559
- 3
- 18
1
vote
1 answer
Data withUnsafeBytes is deprecated
I got this code here from an app I am working on. I inherited this code when the BLE guy left the team. I am not good with low level stuff and Data stuff. I am UI/UX front end person, and now I do need to get my hands dirty. This code is now a bit…
Pascale Beaulac
- 889
- 10
- 28
1
vote
1 answer
Rust: how to tell the borrow checker that the move is depend on a bool?
The following code doesn't pass the borrow checker, for Label-A uses a value that consumed by Label-B, but the code is actually safe: the Label-A is guarded with processed which is only set if Label-B is run.
How can I tell the compiler the…
Incömplete
- 853
- 8
- 20
1
vote
1 answer
Convert Data into UnsafeRawPointer and vice versa in swift
I have been working on an app that uses Pencil Kit and I am trying to store a drawing on the canvas into a sqlite3 database. In order to do so, I had to convert the drawing(type: Data) into an UnsafeRawPointer. However, after the conversion, when I…
Clare
- 71
- 6
1
vote
0 answers
Using the Objective-C runtime in Swift to dynamically call Objective-C methods returns invalid UnsafePointer
I am attempting to use the Objective-C runtime in Swift to dynamically call Objective-C methods using method_getImplementation. My approach works well for methods that either return void or that return an object, but it breaks when attempting to…
S.Moore
- 1,277
- 17
- 17