c - gcc detect duplicate symbols/functions in static libraries

Question

Is there any way we can get gcc to detect a duplicate symbol in static libraries vs the main code (Or another static library ?)

Here's the situation:

main.c erroneously contained a function definition, e.g. with the signature uint foohash(const char*)

foo.c also contains a function definition with the signature uint foohash(const char*)

foo.c and other source files are compiled to a static util library, which the main program links in, i.e. something like:

 gcc -o main main.o util.o -L ./libs -lfooutils

So, now main.o and libs/libfooutils.a both contain a foohash function. Presumably the linker found that symbol in main.o and doesn't bother looking for it elsewhere.

Is there any way we can get gcc to detect such a situation ?

Answer 1

Indeed as Simon Richter stated, --whole-archive option can be useful. Try to change your command-line to:

 gcc -o main main.o util.o -L ./libs -Wl,--whole-archive -lfooutils -Wl,--no-whole-archive

and you'll see a multiple definition error.