Misuse of unsafe.Pointer

Why This Happens

The unsafe.Pointer type allows bypassing Go's type system. However, storing a uintptr (the integer form of a pointer) in a variable is dangerous because the garbage collector does not track uintptr values. The original memory may be reclaimed. Always convert in a single expression.

The Problem

func getFieldPtr(s *MyStruct) *int {
    ptr := uintptr(unsafe.Pointer(s))
    ptr += unsafe.Offsetof(s.Field)
    // GC may move s between these lines!
    return (*int)(unsafe.Pointer(ptr))
}

The Fix

func getFieldPtr(s *MyStruct) *int {
    return (*int)(unsafe.Pointer(
        uintptr(unsafe.Pointer(s)) + unsafe.Offsetof(s.Field),
    ))
}

Step-by-Step Fix

1. 1

   Identify the unsafe.Pointer usage

   Find code that stores uintptr values in variables before converting back to pointers.

2. 2

   Combine into single expression

   Perform the entire pointer arithmetic in a single expression without intermediate uintptr variables.

3. 3

   Consider safer alternatives

   Check if reflect or encoding/binary can achieve the same goal without unsafe.