LNK2005 error with vector

This blog Cubic suggested trying four things and then more or less asking for help

Rebuild, check
check Runtime Libraries, only have one project
check entry point, check SUBSYSTEM:CONSULE
check for force included .lib files, I do not see #pragma comment(lib, ...)
something about turning on /VERBOSE in the linker options, I do not see the option

I would post some code but this is a LNK error ; it does not give much information.

LNK2005: "class std::vector,class std::allocator >,class std::allocator,class std::allocator > > >,class std::allocator,class std::allocator >,class std::allocator,class std::allocator > > > > > list1" (?list1@@3V?$vector@V?$vector@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@V?$allocator@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@2@@std@@V?$allocator@V?$vector@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@V?$allocator@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@2@@std@@@2@@std@@A) already defined in msproject.obj
LNK2005: "class std::vector,class std::allocator >,class std::allocator,class std::allocator > > >,class std::allocator,class std::allocator >,class std::allocator,class std::allocator > > > > > list1" (?list1@@3V?$vector@V?$vector@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@V?$allocator@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@2@@std@@V?$allocator@V?$vector@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@V?$allocator@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@2@@std@@@2@@std@@A) already defined in msproject.obj

I see that it is something about vector already defined in msproject - I made sure the vectors have different names. Is this something with the header # include <vector>; I tried commenting out some of the #includes to check, but same.

Solution

Seems like you're defining list1 more than once. (btw, the name suggests it should be a std::list, but that's beyond the scope of the question)

Do you have a

std::vector<std::string> list1;

in a header file? Is that header included in multiple translation units?

If you want a global, you need to use extern in the header:

extern std::vector<std::string> list1;

and move the definition in a single implementation file.