GCC 4.2 Build error

Question

Hi, i am building a C project with Xcode and when ever i build it it gives me this error:

ld: duplicate symbol _detectLinux in /Users/markszymanski/Desktop/Programming/C/iTermOS/build/iTermOS.build/Debug/iTermOS.build/Objects-normal/i386/linuxDetect.o and /Users/markszymanski/Desktop/Programming/C/iTermOS/build/iTermOS.build/Debug/iTermOS.build/Objects-normal/i386/iTermOS.o

Thanks!

Answer 1

This means you have defined the same symbol with global scope in (at least) two different source files -- either a function or a global variable called _detectLinux, and apparently in the files linuxDetect.c and iTermOS.c.

How to fix it depends on how you intend to use this symbol:

• If you meant to define it in one file and use it in the other file, declare it extern in the other file.

• If you only intend to use the symbol in the file that it is declared in, you can declare it static.

• If the symbol is defined in both files, you can rename the symbol in one (or both) files.

Answer 2

Well, that's not much information to go on. As the error says, the symbol _detectLinux is included in both linuxDetect.o and iTermsOS.o and when you try to link them together, there is a conflict since the linker does not know which of the two symbols to use. This might happen if you, for example, have a global variable with that name in a .h file which is used to build both files instead of declaring it in one place and declaring it as "extern" in the .h file.

What you need to do is look at where the symbol _detectLinux is originally declared, then trace through the dependencies for both linuxDetect.o and iTermOS.o to see why it is being included publicly in both.

Answer 3

If _detectLinux is a function, one common way to get this problem is to define it in a header file but forget to mark it inline. This would cause it to generate the function code in each file that includes the header (presumably _detectLinux.c and iTermsOS.c).

Alternately perhaps you copy-pasted the entire body of the function between the two source files instead of simply declaring the function in iTermsOS.c where I expect it's being called.