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More get / getOr improvements

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- Use `const K`, not `K`, otherwise we don't get auto referencing of
  rvalues.

- Generalized the deleted overloads, because we don't care what the key
  type is --- we want to get rid of anything that has an rvalue map
  type.
This commit is contained in:
John Ericson 2025-09-15 12:25:37 -04:00
parent 2b0fd88324
commit f3e3f75838
1 changed files with 13 additions and 10 deletions
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23
src/libutil/include/nix/util/util.hh
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@ -197,7 +197,7 @@ std::pair<std::string_view, std::string_view> getLine(std::string_view s);
* Get a value for the specified key from an associate container. * Get a value for the specified key from an associate container.
*/ */
template<class T, typename K> template<class T, typename K>
const typename T::mapped_type * get(const T & map, K & key) const typename T::mapped_type * get(const T & map, const K & key)
{ {
auto i = map.find(key); auto i = map.find(key);
if (i == map.end()) if (i == map.end())
@ -206,7 +206,7 @@ const typename T::mapped_type * get(const T & map, K & key)
} }
template<class T, typename K> template<class T, typename K>
typename T::mapped_type * get(T & map, K & key) typename T::mapped_type * get(T & map, const K & key)
{ {
auto i = map.find(key); auto i = map.find(key);
if (i == map.end()) if (i == map.end())
@ -214,15 +214,17 @@ typename T::mapped_type * get(T & map, K & key)
return &i->second; return &i->second;
} }
/** Deleted because this is use-after-free liability. Just don't pass temporaries to this overload set. */ /**
template<class T> * Deleted because this is use-after-free liability. Just don't pass temporaries to this overload set.
typename T::mapped_type * get(T && map, const typename T::key_type & key) = delete; */
template<class T, typename K>
typename T::mapped_type * get(T && map, const K & key) = delete;
/** /**
* Get a value for the specified key from an associate container, or a default value if the key isn't present. * Get a value for the specified key from an associate container, or a default value if the key isn't present.
*/ */
template<class T, typename K> template<class T, typename K>
const typename T::mapped_type & getOr(T & map, K & key, const typename T::mapped_type & defaultValue) const typename T::mapped_type & getOr(T & map, const K & key, const typename T::mapped_type & defaultValue)
{ {
auto i = map.find(key); auto i = map.find(key);
if (i == map.end()) if (i == map.end())
@ -230,10 +232,11 @@ const typename T::mapped_type & getOr(T & map, K & key, const typename T::mapped
return i->second; return i->second;
} }
/** Deleted because this is use-after-free liability. Just don't pass temporaries to this overload set. */ /**
template<class T> * Deleted because this is use-after-free liability. Just don't pass temporaries to this overload set.
const typename T::mapped_type & */
getOr(T && map, const typename T::key_type & key, const typename T::mapped_type & defaultValue) = delete; template<class T, typename K>
const typename T::mapped_type & getOr(T && map, const K & key, const typename T::mapped_type & defaultValue) = delete;
/** /**
* Remove and return the first item from a container. * Remove and return the first item from a container.