c++ - Can a unique_ptr<>() initialization fail? -

from documentation of std::unique_ptr<>(), may happen when initializing pointer not clear me.

when allocating std::shared_ptr<>(), allocates memory buffer handle reference counter. may std::bad_alloc exception.

could similar happen when initializing unique pointer?

i asking question because if does, may lose attempting have delete through unique pointer. example:

void deleter(file * f) {   fclose(f); }  void func() {   ...   file * f(fopen("/tmp/random", o_creat | ...));   if(f == nullptr) ...handle error...   std::unique_ptr<file, decltype(&deleter)> raii_file(f, deleter);   ... } 

so, if initialization of unique_ptr<>() can throw, may end keeping file f open forever. (i use file * example, similar resource affected.)

opposed this answer, cannot use std::make_unique<>() since i'm not allocating memory.

would safer initialize std::unique_ptr<>() before fopen(), , save value in there after?

  ...   std::unique_ptr<file, decltype(&deleter)> raii_file(nullptr, deleter);   file * f(fopen("/tmp/random", o_creat | ...));   if(f == nullptr) ...handle error...   raii_file = f;   ... 

or have similar problems?

all of unique_ptr's constructors noexcept. no, there's no way can fail. if deleter type throws on copy/move, noexcept catch , call std::terminate.