CODEWITHSUNDEEP
c++c++11g++unordered-map
smatter
smatter

Reputation: 29248

Using unordered_map of C++0x

I am using an unordered_map which is included as: #include <unordered_map> and the program is compiled as follows: g++ Test.cc -std=gnu++0x -o test Am I using the unordered_map of TR1 or that of C++0x. Or is it both the same?

Upvotes: 5

Views: 3343

Answers (3)

Kerrek SB
Kerrek SB

Reputation: 477600

This depends very much on the particular compiler version. For instance, GCC 4.4 basically just had some macro switches for your -std=c++0x option to do the namespace labelling appropriately, but would always end up pulling the actual code from tr1_impl/unordered_map, while GCC 4.6 has two entirely separate implementations, one in tr1/unordered_map.h and one in bits/unordered_map.h -- and the respective base class implementations in .../hashtable.h do in fact differ; the C++0x version has std::forwards everywhere etc.

Short answer: It depends.

Upvotes: 0

emsr
emsr

Reputation: 16373

GCC has tr1 headers in tr1 subdirectory. Plus there is the tr1 namespace.

#include <tr1/unordered_map>
...
std::tr1::unordered_map<...>(...);

So unless you specifically did these things or did a similar "using" you've got the std ones.

The implementations are split but they are rather similar. There were just enough differences (initializer_list, comparison ops) to make maintenance of one file with all the conditionals and macros a pain.

Upvotes: 3

Howard Hinnant
Howard Hinnant

Reputation: 219438

I believe gcc puts their TR1 headers in <tr1/unordered_map>, so you should be getting the C++11 version. But they are very similar.

Upvotes: 6

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