go runtime_error ai_generated true

panic: runtime error: invalid memory address or nil pointer dereference

ID: go/unsafe-pointer-arithmetic

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80%Fix Rate
85%Confidence
0Evidence
2024-05-12First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.21 active — — —
1.22 active — — —

Root Cause

Using `unsafe.Pointer` arithmetic incorrectly, resulting in accessing out-of-bounds memory.

generic

中文

错误地使用`unsafe.Pointer`算术，导致访问越界内存。

Workarounds

  1. 90% success Use `unsafe.Add` for safe pointer arithmetic (Go 1.17+) 
    p := unsafe.Pointer(&arr[0])
next := unsafe.Add(p, unsafe.Sizeof(arr[0])*2)
_ = *(*int)(next)
  2. 75% success Convert to `uintptr` only immediately before use and pin 
    runtime.KeepAlive(arr)
ptr := uintptr(unsafe.Pointer(&arr[0])) + unsafe.Sizeof(arr[0])
_ = *(*int)(unsafe.Pointer(ptr))

Dead Ends

Common approaches that don't work:

  1. Adding offset without aligning to type size 70% fail

    Unaligned access can cause crash on some architectures.

  2. Using `uintptr` as pointer without pinning 80% fail

    GC may move the object, making uintptr stale.