Michael Tautschnig <m...@debian.org> writes: > The package build process produces an archive libwmlscript.a as follows: > > ar rc libwmlscript.a wmlscript/wmlsc.o ... > > with wmlsc already containing a "main" function. Subsequently libwmlscript.a > is > linked to multiple object files containing their own main function (including > wmlscript/wmlsc.o, again), which leads to duplicate definitions of main, and > thus undefined behaviour as the linker is free to pick either of them.
I don't believe there is undefined behaviour in this case. Details below. Regardless, fixing this would make the sources easier to understand. The linker does not link all the members of libwmlscript.a into the output file, only those that satisfy undefined references. So although libwmlscript.a(wmlsc.o) and libwmlscript.a(wmlsdasm.o) both define a main function, the linker links neither of those because it already has a main function from the wmlsc.o that was specified in the command line, and those members do not satisfy any other undefined references either. libwmlscript.a(wmlsdasm.o) also defines a lookup_function symbol. If you add the -Wl,--undefined=lookup_function option to the gcc command that links wmlscript/wmlsc from wmlscript/wmlsc.o, libwmlscript.a, and other archives, then the linker will link libwmlscript.a(wmlsdasm.o) in order to satisfy the reference to lookup_function. That then causes an error: libwmlscript.a(wmlsdasm.o): In function `main': /home/kalle/build/kannel/wmlscript/wmlsdasm.c:98: multiple definition of `main' wmlscript/wmlsc.o:/home/kalle/build/kannel/wmlscript/wmlsc.c:115: first defined here collect2: error: ld returned 1 exit status Because that error does not normally occur during the build, I think it is clear that the linker normally links neither libwmlscript.a(wmlsc.o) nor libwmlscript.a(wmlsdasm.o) into the output file wmlscript/wmlsc. If you instead removed wmlscript/wmlsc.o from the command line, then the linker would try to find a main function in the archives, and I think it could choose either libwmlscript.a(wmlsc.o) or libwmlscript.a(wmlsdasm.o). I think that would be undefined behaviour. -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
