Update unsafe code doc #47124
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Update unsafe code doc #47124
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BillWagner
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Jul 17, 2025
| type* identifier; | ||
| void* identifier; //allowed but not recommended |
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This is legal, and this is the reference, so we should leave this here.
| There are several examples of pointers in the articles on the [`fixed` statement](statements/fixed.md). The following example uses the `unsafe` keyword and the `fixed` statement, and shows how to increment an interior pointer. You can paste this code into the Main function of a console application to run it. These examples must be compiled with the [**AllowUnsafeBlocks**](compiler-options/language.md#allowunsafeblocks) compiler option set. | ||
| - `int* p`: pointer to `int` | ||
| - `int** p`: pointer to pointer to `int` | ||
| - `int*[] p`: array of `int` pointers |
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For consistency, I'd use "pointers to int"
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| - `int*[] p`: array of `int` pointers | |
| - `int*[] p`: array of pointers to `int` |
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| You can't apply the indirection operator to a pointer of type `void*`. However, you can use a cast to convert a void pointer to any other pointer type, and vice versa. | ||
| Pointers don't inherit from [`object`](builtin-types/reference-types.md). You can't box or unbox pointers, and there's no conversion between pointers and `object`. However, you can cast between pointer types and between pointers and integral types (with an explicit cast). |
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And, we do need to add void* conversions (reference), with appropriate "danger, not recommended" language.
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| :::code language="csharp" source="snippets/unsafe-code/Conversions.cs" ID="Conversion"::: | ||
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| ### Pointer safety reminders | ||
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| - Dereferencing a null pointer is implementation-defined and may crash your program. |
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Because this is the language reference for our implementation, we should say what we do on all platforms here.
I'll defer to others, but I think it's consistent, but platform dependent. The null value is defined as all 0's. IIRC, all platforms we support have an OS level exception for that operation.
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Updating unsafe code doc to reflect our current thinking.
Related:
@EgorBo
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