I'm trying to figure out how to use static libraries, but the most trivial example fails:
//foo.c
int func(int i) {
return i+1;
}
//main.c
int func(int i);
int main() {
return func(41);
}
Compiling foo.c and main.c works:
gcc -Wall -o foo.o -c foo.c
gcc -Wall -o main.o -c main.c
Archiving foo.o does not complain either:
ar rcs libfoo.a foo.o
But Linking fails with an undefined reference to func:
ld libfoo.a main.o
ld -L. -lfoo main.o
both give me:
ld: warning: cannot find entry symbol _start; defaulting to 00000000004000b0
main.o: In function `main':
main.c:(.text+0xa): undefined reference to `func'
I get a similar error if I take the detour via gcc to link:
gcc libfoo.a main.o
gcc -L. -lfoo main.o
give me:
main.o: In function `main':
main.c:(.text+0xa): undefined reference to `func'
collect2: ld returned 1 exit status
What am I doing wrong here? According to all manuals and search engines I read/used this is the way to use static libraries.
Edit: Mind that gcc foo.o main.o works perfectly fine.
After a lot of trying stupid stuff, the most stupid idea was the solution: ld wants the object files first, then the archives. Yay!
gcc libfoo.a main.o // fails
gcc main.o libfoo.a // works
The same goes if you specify the library with -L. and -lfoo: Where you put -L doesn't matter apparently, but where you put -lfoo matters to the same extent as if you specify the .a file directly.