[diff.cpp17.containers]

# Annex C (informative) Compatibility [[diff]](./#diff)

## C.3 C++ and ISO C++ 2017 [[diff.cpp17]](diff.cpp17#containers)

### C.3.11 [[containers]](containers "23 Containers library"): containers library [diff.cpp17.containers]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/compatibility.tex#L1387)

**Affected subclauses:** [[forward.list]](forward.list) and [[list]](list)  


**Change:** Return types of remove, remove_if, and unique changed from void to container​::​size_type[.](#1.sentence-1)

  


**Rationale:** Improve efficiency and convenience of finding number of removed elements[.](#1.sentence-2)

  


**Effect on original feature:** Code that depends on the return types might have different semantics in this revision of C++[.](#1.sentence-3)

Translation units compiled against this version of C++ may be incompatible with
translation units compiled against C++ 2017, either failing to link or having undefined behavior[.](#1.sentence-4)