包括Boost文件系统头

Question

I have a big project.

In N.cpp I need to use boost::filesystem::exists(path) to check if the path is valid.

For that, I include <boost/filesystem.hpp>

I get the following error:

Error    2    error LNK2005: "public: enum boost::filesystem::file_type __cdecl boost::filesystem::file_status::type(void)const " (?type@file_status@filesystem@boost@@QEBA?AW4file_type@23@XZ) already defined in N.obj    D:\MProject\DA\boost_filesystem-vc100-mt-gd-1_53.lib(boost_filesystem-vc100-mt-gd-1_53.dll)    DA

Error    1    error LNK2005: "public: __cdecl boost::filesystem::path::~path(void)" (??1path@filesystem@boost@@QEAA@XZ) already defined in N.obj    D:\MProject\DAboost_filesystem-vc100-mt-gd-1_53.lib(boost_filesystem-vc100-mt-gd-1_53.dll)    DA

Error    3    error LNK1104: cannot open file 'libboost_filesystem-vc100-mt-gd-1_53.lib'    D:\MProject\DA\LINK    DA

If I do not include the header file, I get:

Error    2    error C3861: 'exists': identifier not found    D:\MProject\DA\ThirdParty\N.cpp    108    1    DA
Error    1    error C2653: 'boost' : is not a class or namespace name    D:\MProject\DA\ThirdParty\N.cpp    108    1    DA

What is the right way to use boost::filesystem::exists so that the whole thing would compile?

N.cpp

#include <boost/filesystem.hpp>
.....
CHECK( boost::filesystem::exists(*i), std::string("file ").append(*i).append(" does not exist").c_str() );

.....

Answer 1

I solved the problem by adding to N.cpp:

#ifndef BOOST_ALL_DYN_LINK
#   define BOOST_ALL_DYN_LINK
#endif 
#include <boost/filesystem.hpp>

Answer 2

If you want to use boost::filesystem you have to include the header file (directly or indirectly via other includes).

The first three errors are linker errors. Some parts of Boost are header-only, ie you don't have to compile Boost when you want to use them. Unfortunately filesystem isn't one of them. That means you have to compile Boost like described here . Afterwards you have to tell your linker where it can find the binaries you just created and it should compile well (if you didn't do any other mistakes ;-) ).