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I'm not sure if it is specified in the standard that advance/dereference of standard container iterator are noexcept. GCC and MSVC consistently make them noexcept for all standard containers. But clang make them noexcept for std::vector/std::basic_string and noexcept(false) for std::list/std::set/std::map/std::unordered_set/std::unordered_map.

Example code could be found below or on godbolt.

#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <vector>
#include <list>
#include <string>
#include <ranges>

template<typename Iterator>
concept nothrow_advancable = noexcept(++std::declval<Iterator&>());

template<typename Iterator>
concept nothrow_dereferencable = noexcept(*std::declval<Iterator&>());

static_assert(nothrow_advancable<std::ranges::iterator_t<std::vector<int>&>>);
static_assert(nothrow_advancable<std::ranges::iterator_t<std::basic_string<char>&>>);
static_assert(nothrow_advancable<std::ranges::iterator_t<std::list<int>&>>); // not noexcept with clang
static_assert(nothrow_advancable<std::ranges::iterator_t<std::set<int>&>>); // not noexcept with clang
static_assert(nothrow_advancable<std::ranges::iterator_t<std::map<int, int>&>>); // not noexcept with clang
static_assert(nothrow_advancable<std::ranges::iterator_t<std::unordered_set<int>&>>); // not noexcept with clang
static_assert(nothrow_advancable<std::ranges::iterator_t<std::unordered_map<int, int>&>>); // not noexcept with clang

static_assert(nothrow_dereferencable<std::ranges::iterator_t<std::vector<int>&>>);
static_assert(nothrow_dereferencable<std::ranges::iterator_t<std::basic_string<char>&>>);
static_assert(nothrow_dereferencable<std::ranges::iterator_t<std::list<int>&>>); // not noexcept with clang
static_assert(nothrow_dereferencable<std::ranges::iterator_t<std::set<int>&>>); // not noexcept with clang
static_assert(nothrow_dereferencable<std::ranges::iterator_t<std::map<int, int>&>>); // not noexcept with clang
static_assert(nothrow_dereferencable<std::ranges::iterator_t<std::unordered_set<int>&>>); // not noexcept with clang
static_assert(nothrow_dereferencable<std::ranges::iterator_t<std::unordered_map<int, int>&>>); // not noexcept with clang
Improve this question
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  • Extra noexcept can be added from vendors, (contrary to constexpr, even if gcc did it). Commented Jan 8 at 14:57
  • From en.cppreference.com/w/cpp/container/list, list::iterator is a BidirectionalIterator, and no mention of noexcept. Commented Jan 8 at 15:00
  • I think being a BidirectionalIterator is not related to evaluating noexcept(++it) and noexcept(*it). Commented Jan 8 at 15:52
  • 1
    Those containers would use sentinel and not past-to-end iterator; that might change something... Commented Jan 8 at 15:57
  • 1
    If you feel clang should "follow the same logic" your best option is to create an issue on clang's bug tracker. If it's straightforward, they'd probably appreciate a pull request. Commented Jan 8 at 16:08
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