difference between cstdint and tr1/cstdint

Question

What is the difference between <cstdint> and <tr1/cstdint>? (apart from that one puts things in namespace std:: and the other in std::tr1::)

Since this stuff isn't standard yet I guess it's compiler specific so I'm talking about gcc. To compile with the non-tr1 one I must compile with -std=c++0x, but there is no such restriction when using tr1.

Is the answer perhaps that there is none but you can't go around adding things to std:: unless there, well, standard. So until c++0x is standardised an error must be issued using <cstdint> but you dont need to worry when adding to the tr1:: namespace, which makes no claim to things in it being standard? Or is there more to this?

Thanks.

p.s - If you read "std" as standard, as I do, I do apologise for the overuse of the word in this Q.

Answer 1

I think you've got it. On my system, they're very similar, but with different macro logic. For instance, /usr/include/c++/4.4/tr1/cstdint has:

#  define _GLIBCXX_BEGIN_NAMESPACE_TR1 namespace tr1 {
#  define _GLIBCXX_END_NAMESPACE_TR1 }
#  define _GLIBCXX_TR1 tr1::

but /usr/include/c++/4.4/cstdint has:

#  define _GLIBCXX_BEGIN_NAMESPACE_TR1
#  define _GLIBCXX_END_NAMESPACE_TR1
#  define _GLIBCXX_TR1

So if it's being included as <cstdint> the TR1 namespace is simply defined into oblivion.

Answer 2

At least as far as I know, there was no intent to change <cstdint> between TR1 and C++0x. There's no requirement for #includeing <cstdint> to result in an error though -- officially, it's nothing more or less than undefined behavior. An implementation is allowed to specify exact behavior, and in this case it does.

Answer 3

<tr1/cstdint> is defined, as name suggests, in TR1, while <cstdint> is defined in c++0x.

From gcc manual, -std=c++0x is needed to enable experimental features that are likely to be included in C++0x. However, <tr1/cstdint> is defined in TR1, not c++0x, so -std=c++0x is no needed.

The following is gcc manual for -std=c++0x for your reference.

The working draft of the upcoming ISO C++0x standard. This option enables experimental features that are likely to be included in C++0x. The working draft is constantly changing, and any feature that is enabled by this flag may be removed from future versions of GCC if it is not part of the C++0x standard.