[libcxx-commits] [libcxx] [libc++] Ensure strong exception guarantee for forward_list::resize (PR #131025)

[Louis Dionne via libcxx-commits]

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@@ -1241,10 +1241,29 @@ void forward_list<_Tp, _Alloc>::resize(size_type __n) {
     erase_after(__p, __e);
   else {
     __n -= __sz;
+    __begin_node_pointer __r = __p.__get_begin();
     if (__n > 0) {
-      for (__begin_node_pointer __ptr = __p.__get_begin(); __n > 0; --__n, __ptr = __ptr->__next_as_begin()) {
-        __ptr->__next_ = this->__create_node(/* next = */ nullptr);
+      __node_pointer __first = this->__create_node(/* next = */ nullptr);
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ldionne wrote:

I wonder if we could use `emplace_after` instead with no `_Args...`? Or maybe we can add an internal version that gets called by both `resize(n)` and `resize(n, value)`?

https://github.com/llvm/llvm-project/pull/131025