withArray 与 newArray
在Haskell FFI中，用withArray和newArray分配的数组有什么本质区别？我在 c 中有一个函数可以与 newArray 一起使用，但与 withArray 一起使用会出现段错误。工作代码看起来有点像这样：
a <- newArray items
fficall a
free a
段错误的代码看起来像这样：
withArray items fficall
当 ffi 进入 blas 函数时，段错误就会发生。由于我不允许显示 c 代码，所以问题是，“请向我展示一个示例 c 函数，该函数也会在 withArray 中出现段错误，但在 newArray 中不会出现段错误”代码>."
In the Haskell FFI, what is the essential difference between arrays allocated with withArray and newArray? I have function in c that works with newArray but segfaults with withArray. The working code looks bit like this:
a <- newArray items
fficall a
free a
The code that segfaults looks like this:
withArray items fficall
The segfault happens up when the ffi enters a blas function. Since I'm not allowed to show the c-code, the question is, "please show me an example c-function that also segfaults with withArray but not with newArray."
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据我所知，newArray最终调用malloc来进行分配，而withArray调用allocaArray，这最终出现在
newAlignedPinnedByteArray#中。也许您的函数依赖于由
malloc分配的内存，例如尝试realloc或free它？From what I can see,
newArrayends up callingmallocto do the allocation, whilewithArraycallsallocaArray, which ends up innewAlignedPinnedByteArray#.Perhaps your function is relying on the memory being allocated by
malloc, for example by attempting toreallocorfreeit?看起来
newArray使用mallocArray在堆上分配数组（需要显式释放），但withArray分配数组使用allocaArray在堆栈上（假设alloca的行为方式与 C 中的行为方式相同），当调用函数返回时，它将被回收。您的列表可能太大，导致（鼓声）堆栈溢出。编辑：嗯，也许不是，看起来
allocaArray使用 haskell 内存管理器而不是C堆在堆中分配固定数组。It looks like
newArrayallocates the array on the heap usingmallocArray(which will need to be free'd explicitly), butwithArrayallocates the array on the stack usingallocaArray(assumingallocabehaves the way it does in C), which will be reclaimed when the calling function returns. It is possible that your list is so large that it has caused a (drum roll) Stack Overflow.Edit: Hmm, maybe not, it looks like
allocaArrayallocates a pinned array in the heap, using the haskell memory manager instead of theCheap.