alt Hacker NewsI find variable-length arrays (i.e. arrays whose length is defined at run-time and typically live on the stack) to be kind of dangerous, and try to avoid them, even in C.
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cksk • today at 11:25 AM
The array at the end of the struct is not a VLA on the stack. When you allocate the struct, you add enough extra to hold the contents of the array. VLAs on the stack are pretty much universally considered a bad idea, as far as I can tell.
A type of VLA I would like to see more of in C code however, is variable-length array parameters (void func(int n, int arr[n]);) and array pointers (int (*my_array)[n];).
Compilers can often do some static bounds-checking of such arrays. But because those features had been introduced together with variable-length array stack variables , people have lumped them all together and thus shunned these features that could otherwise have added safety.
BTW, one thing you should never do is use variable-length array declarations and alloca() in the same function. As VLA variables have scope life-time and allocas have function life-time they are not compatible — and allocations could overlap. Yet, not all compilers (/versions) that support both warn when they are used together.