Questions tagged [stackalloc]
C# operator that allocates a block of memory on the stack
stackalloc
43
questions
5
votes
1
answer
198
views
What is the most efficient way to create a temporary collection? Differences between stackalloc, and collection expressions?
In C# there are now multiple ways to create a temporary collection.
You can just new an array and hope the garbage collector doesn't mind.
// Just create a new array
Span<int> array = new int[]{ ...
- 9,558
1
vote
0
answers
104
views
C#: of two methods which calculate Levenshtein distance, why does the heap-allocated "cost" array outperform the stack-allocated "cost" array?
Consider the following C# implementation (not my own) for Levenshtein distance: "Fastenshtein/StaticLevenshtein.cs". I removed the original comments and eliminated some whitespace for ...
- 71
2
votes
0
answers
146
views
unknown function in decompiled dll
I'm trying to decompile a dll which is in .net 4.6. After using de4dot to decompile and deobfuscate the dll there are bunch of classes in it. I came across two functions(?) named __fieldref and ...
- 33
7
votes
1
answer
390
views
What is an efficient equivalent in C# for Span<Span<T>>, which does not exist?
I was porting some older high-speed C++ code to C#, and the existing code made use of a pointer-based double-indirection pattern like this (written here in a C# syntax), using the stack as efficient ...
- 6,006
0
votes
1
answer
78
views
Rapid stack allocations vs accessing a single heap allocation
I'm having a situation where I have an array T[] which must be copied in an instant and sent over to a function accepting a ReadOnlySpan<T>. I found two solutions on this problem. However I'm ...
- 137
3
votes
0
answers
398
views
Can I suppress .local for stackalloc in C# without using unsafe?
To allocate a double array initialized to zero, you can choose
var x = new double[N];
to allocate on the heap and
Span<double> x = stackalloc double[N];
to allocate on the stack.
To suppress ...
- 101
0
votes
0
answers
55
views
Is there a way, to conditionally allocate some fixed-size-stack buffer?
pretty much tittle!
imagine this here:
public unsafe ConditionalAllocOnStack
{
private fixed byte STACK[CONDITION_TRUE ? 100 : 0];
public ConditionalAllocOnStack()
{
//....
} ...
- 83
0
votes
0
answers
83
views
Garbage data after stackalloc field initializer
I am using .NET 6.0 on Windows 10 with Visual Studio 2022 last Version, last Build, and this code runs fine and even SEEMINLGY does what I want: have a look:
But: keep a closer look on the "Init(...
- 83
4
votes
1
answer
265
views
What is the return type of a stackalloc espression?
I'm playing with stackalloc and finding a lot of weirdness in its return type. Here are some examples using stackalloc<float>:
1. Implicit typing returns float*:
var a = stackalloc float[1];//a ...
- 3,161
1
vote
1
answer
138
views
What happens when I assign a `ref` value to an `out` argument in C#?
I am writing an class that retrieves binary data and supports generically converting it into primitive types. It's supposed to be as efficient as possible. Here is what it looks like right now:
public ...
- 58
5
votes
1
answer
750
views
Why a `stackalloc` expression cannot be assigned to a `Span<T>` parameter?
Consider the following methods (fiddle):
void test(Span<int> param)
{
//Fail, the stackalloc'ed buffer could be exposed.
param = stackalloc int[10];
}
void test2(Span<int> param)
{...
- 43.3k
53
votes
2
answers
4k
views
Why does a zero-length stackalloc make the C# compiler happy to allow conditional stackallocs?
The following "fix" is very confusing to me; the scenario here is conditionally deciding whether to use the stack vs a leased buffer depending on the size - a pretty niche but sometimes-...
- 1.1m
0
votes
0
answers
268
views
Why do I have padding in the stack?
I was trying to understand how the stack (segment) works and thought that it will simply allocate each element (variable, byte, whatever I want to allocate) one after another. BUT after writing ...
user12722843
0
votes
1
answer
972
views
How to use C# stackalloc and keep the same code structure?
I have a method MemRead that reads memory and returns a byte array
[DllImport("kernel32.dll", SetLastError = true)]
internal static extern bool ReadProcessMemory(IntPtr hProcess, IntPtr lpBaseAddress,...
- 910
0
votes
1
answer
360
views
Allocation-free enumeration and processing
I would like to solve the massive allocation costs of a c# application.
The application itself can be represented by the TickUser class at the bottom, and I'd like to know how to implement the ...
- 4,949