How to compile and link together object files in C++ using the same header file?

c++, gcc, object

Solution

There is no issue, you've got an error in your gcc syntax.

g++ -c foo1.cc
g++ -c foo2.cc
g++ -o foo foo1.o foo2.o

the `-o` parameter accepts name of the output file, so in your case, it would overwrite foo1.o with result of linkage.

Problem

I'm having this issue where the GCC compiler seems to be failing when it comes to linking two object files I have together. Both object files `foo1.cc` and `foo2.cc` include classes from a header file called `foo1.hh`. In addition, the header file `foo.hh` has as an external declaration of an object instance that appears in `foo1.cc`. It should be noted that the header file `foo.hh` will only be defined once between the two source files `foo1.cc` and `foo2.cc`. When I compile the source files using the following command, everything seems to work: ``` g++ foo1.cc foo2.cc ``` The above command will produce an executable called `a.out`. When I try to compile the source files into object files independently: ``` g++ -c foo1.cc g++ -c foo2.cc g++ -o foo1.o foo2.o ``` The GCC compiler complains that there are undefined references to functions in `foo2.cc`. These functions should be defined in `foo1.cc`; however, the linker doesn't recognize that. I was wondering if there was a way to get around this issue with the GCC compiler.

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