On Mon, Jan 15, 2018 at 10:35 PM, chenzhelu <chenz...@netease.com> wrote: > Hello all, > I encountered a problem on "local class name conflict", > I searched on net and found that years ago, some people also encoutered this > kind of problem.
The correct name for this is One Definition Rule (or ODR for short). Basically a violation of this rule causes the code to be invalid (with no diagnostic required; therefor undefined code). If you use LTO, GCC sometimes will warn about this violation. If you want a truly local class, then use anonymous namespaces which is designed to fix this issue. Thanks, Andrew > > https://stackoverflow.com/questions/10671956/same-class-name-in-different-c-files > http://www.cplusplus.com/forum/general/32010/ > > > Please see the following code, (BTW, it seems that the maillist can not > attach files) > > When I ran the code(Ubuntu 64bis, gcc vesion:5.4.0, the amazing result is : > localClassXInData.cpp in Data.cpp > localClassXInData.cpp in Data.cpp > > > I think there is an error in Link phrase: > 1. if comment out the LocalClassX definition in main.cpp, the compile will > not compile the code --- this is as expected. > 2. however, if run the code(not comment out any code), the code actually ran > is in the Data.cpp, that is not consistent with compile phase. > > > Thanks! > > > code > //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > // main.cpp > > //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > #include <stdio.h> > #include <stdlib.h> > > #include <string> > using namespace std; > > class LocalClassX > { > public: > string name; > > LocalClassX() { > name = "localClassXInMain.cpp" ; > } > > virtual ~LocalClassX() { > } > > virtual void f() { > printf("%s in main.cpp \n ", name.c_str()); > } > }; > > #include "Data.h" > Data data; > > int main(int argc, char* argv[]) > { > try { > LocalClassX x; > x.f(); > data.add(1); > } > catch (...) { > printf("error \n"); > return 1; > } > return 0; > } > > > //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > // Data.h" > //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > #ifndef DataH > #define DataH > > #include <vector> > #include <string> > using namespace std; > > > class Data { > protected: > vector<int> data; > public: > Data(); > virtual ~Data(); > > void add(int i); > }; > > #endif > > > //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > // Data.cpp > > //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > #include <stdio.h> > > #include "Data.h" > > Data::Data() > { > } > Data::~Data() > { > } > > class LocalClassX > { > public: > string name; > > LocalClassX() { > name = "localClassXInData.cpp" ; > } > > virtual ~LocalClassX() { > } > > virtual void f() { > printf("%s in Data.cpp \n ", name.c_str()); > } > }; > > void Data::add(int i) > { > LocalClassX x; > x.f(); > > data.push_back(i); > } >
