link error while sharing global variables between projects in the same solution

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I want to make a global variable that is shared between 2 projects in the same solution.

I've declared in one cpp file
int x;
and in the other cpp in the second project
extern int x;

the link error was:
error LNK2005: "int x" (?x@@3HA) already defined in CG_skel_w_MFC.obj

Posted 15-Dec-11 12:03pm

stigersh

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CPallini 15-Dec-11 18:17pm

Please give some more details (e.g. the names of the source files using such variable). Please note: global variables should be avoided and, in any case, should have an 'avoiding conflict' name, for istance '__bull5h1_t' is good while 'x' is poor.

Chuck O'Toole 15-Dec-11 20:28pm

both modules need to declare "x" as extern. That way, the module with the definiton "offers the variable to the global linker name space" while the other module "looks for something appearing in the global linker name space"

Albert Holguin 16-Dec-11 9:38am

I hope you're just testing with the 'x' label on a global... that's a horrible name for a variable on the global space (although you should try to avoid globals anyway).

[no name] 16-Dec-11 23:43pm

I think KarstenK's answer makes sense.

3 solutions

Solution 2

Read AV Rule 139 (p.47) from Joint strike fighter air vehicle C++ coding standards[^]. "... this rule will normally mean declaring external objects in header files which will then be included in all those files that use those objects (including the files which define the objects)."

Posted 16-Dec-11 1:50am

Sergey Chepurin

v2

Solution 3

Thanks for the answer, but I still get an error..
error LNK2001: unresolved external symbol

Posted 16-Dec-11 12:30pm

stigersh

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Albert Holguin 17-Dec-11 9:54am

Dont post this as a solution, either update your question or reply to a specific post.

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KarstenK · Accepted Answer · 2011-12-15T22:31:00

Solution 1

declare the extern variable in a common header and implement it in one cpp

Posted 15-Dec-11 22:31pm

KarstenK

Comments

[no name] 16-Dec-11 23:44pm

My 5!