gcc - linking multiple c files to a c++ file

Question

How do you link 2 c library files, to a c++ file?

Right now I am doing this:

> gcc -c file1.c (this works fine) 

> gcc -c file2.c ( this works fine)

> g++ -c myc++file.cpp (this works fine)

> g++ -o program myc++file.o file1.o file2.o

-> I get an error on this last one saying that their is a undefined reference to a function in myc++file.o, but that function is defined in file2.o. Something is wrong, but I just cant figure it out.

Any ideas?

score 3 · Accepted Answer · answered Jan 29 '12 at 21:13

3

Is this function static?

Did you use extern "C" in myc++file.cpp?

if the answers is no and yes, show us some code.

(By the way, try to check using nm if that function is really in file2.o)

answered Jan 29 '12 at 21:13

asaelr

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Technically both of you are right, thanks alot for the quick repsonse. I saw you responded first. For anyone else with this same problem, this answer is good, then also look at this link: http://stackoverflow.com/questions/3789340/combining-c-and-c-how-does-ifdef-cplusplus-work – bryan sammon Jan 29 '12 at 21:34

score 2 · Answer 2 · answered Jan 29 '12 at 21:13

You need to use extern "C" on the function's declaration.
When C++ sees an external function, it mangles the name, to identify the parameter and return value types. When trying to link it with C code, the names don't match.
extern "C" tells C++ not to mangle the name, so it would successfully link with C code.

gcc - linking multiple c files to a c++ file

2 Answers2