1This document present the STLport namespace schema and give additionnal 2information about how STLport replace the native C++ Standard library 3coming with your compiler. 4 51. What is the STLport namespace ? 6 7 As STLport is a C++ Standard library implementation the STLport namespace 8is 'std'. In normal use this is all you need to know and you can stop reading 9here. 10 112. How does STLport replace native C++ Standard library ? 12 13 STLport defines a macro 'std' that replaces all references of std in the 14user code by a different name. This technique has has some drawback but also 15advantages. The drawback is that you cannot declared Standard component like 16that: 17 18 19//foo.h 20namespace std 21{ 22 template <class _Tp> 23 class allocator; 24} 25 26void f1(const std::allocator<int>&); 27 28 29//foo.cpp 30#include "foo.h" 31#include <memory> 32 33void f1(const std::allocator<int>& alloc) 34{ 35 //implementation 36} 37 38//bar.cpp 39#include "foo.h" 40#include <memory> 41 42int main(int, char**) 43{ 44 std::allocator<int> alloc; 45 f1(alloc); 46} 47 48 If you build this code you will surely have a compilation error as f1 is declared 49as taking a std::allocator parameter but you are calling it using an STLport allocator 50instance that is not in the std namespace. The good news is that this drawback is easy 51to detect as it will generate compilation error or at least link time error. The only 52workaround is to include an arbitrary Standard header before the allocator declaration. 53Good candidates for that are <utility> or <cerrno> as they are small headers. Including 54those headers will replace std with the STLport namespace. 55 56 The advantage of this macro replacement is that we can customize the STLport namespace 57depending on the compilation options. For instance the STLport safe mode you can use by 58defining _STLP_DEBUG is not binary compatible with a normal debug build. To ensure that 59no one will ever build code without _STLP_DEBUG and link with STLport library built with 60this option the namespace is different so that it will generate link time error rather 61than random crashes during application execution. 62 633. Why not having use namespace injection ? 64 65 An other way to replace native Standard C++ library implementation would have been to 66use namespace injection: 67 68namespace std 69{ 70 using namespace stlport; 71} 72 73 This solution has a first major drawback which is that STLport would be much more sensible 74to native headers. If you include a C++ native headers that indirectly define for instance 75the vector class it is going to conflict with the STLport vector definition. 76 77 Moreover this solution just does not work for a very simple reason. The C++ Standard 78allows users to specialized some of the Standard algorithms. This specialization has to 79be done in the same namespace as the main template declaration: 80 81//In an STLport header: 82namespace stlport 83{ 84 template <class _Tp> 85 struct less 86 { 87 bool operator () (const _Tp& x, const _Tp& y) const; 88 }; 89} 90 91//User code: 92 93struct MyStruct; 94 95namespace std 96{ 97 template <> 98 struct less<MyStruct> 99 { 100 }; 101} 102 103As you can see the specialization is not in the STLport less namespace and it 104won't be used in associative containers for instance. 105 1064. What is the STLport specific namespace ? 107 108 The official STLport namespace is: stlport. Once again this is not the real namespace 109where all the Standard stuff are. As the real STLport namespace change depending on compilation 110options you cannot use it directly. So stlport is an alias of the real STLport namespace. 111 1125. What are the other STLport namespaces ? 113 114 Those names are given for information purpose and should never be used in any user code. The 115default STLport namespace is: stlp_std. Here is the list of the customized namespaces: 116 117 - stlpd_std : when _STLP_DEBUG is defined 118 - stlpx_std : when you use STLport as a shared library linked to the static version of the native 119 runtime or when you build the static STLport library linked with the dynamic version. This option 120 is only supported by a limited number of compilers. 121 - stlpmtx_std : when building STLport as not thread safe. 122 123 You can also have combination of those extension like stlpdxmtx_std or stlpdmtx_std... 124 125 There is also an other STLport namespace for STLport internal functions or struct/class: priv. 126 127namespace stlport 128{ 129 namespace priv 130 { 131 } 132} 133 134