On Fri, 8 Sep 2006, Hugh Sasse wrote: > On Fri, 8 Sep 2006, Rupert Wood wrote: > > > Hugh Sasse wrote: > > > The second one seems to be a linker problem, since it is complaining > > > about the library file itself. Other programs seem to be working > > > with PNG images correctly, however. > > > > It's complaining that it can't find deflate, which is defined in libz. Link > > order is significant: you must link libz *after* you link libpng since > > libpng depends on it. > > Oh, I thought it would have to be first for precisely that reason :-) > > Is there something that will help me sort these directives correctly? I have a solution to the oringinal prolem now thanks to Nobu Nakada in the Ruby community. The -l options must all occur after the .o files. The GCC manual does say [http://gcc.gnu.org/onlinedocs/gcc-4.1.1/gcc/Link-Options.html#Link-Options] <quote> -l library Search the library named library when linking. (The second alternative with the library as a separate argument is only for POSIX compliance and is not recommended.) It makes a difference where in the command you write this option; the linker searches and processes libraries and object files in the order they are specified. Thus, `foo.o -lz bar.o' searches library `z' after file foo.o but before bar.o. If bar.o refers to functions in `z', those functions may not be loaded. [...] Normally the files found this way are library files.archive files whose members are object files. The linker handles an archive file by scanning through it for members which define symbols that have so far been referenced but not defined. But if the file that is found is an ordinary object file, it is linked in the usual fashion. The only difference between using an -l option and specifying a file name is that -l surrounds library with `lib' and `.a' and searches several directories. </quote> But this is way after earlier advice that: <quote> You can mix options and other arguments. For the most part, the order you use doesn't matter. Order does matter when you use several options of the same kind; for example, if you specify -L more than once, the directories are searched in the order specified. </quote> at http://gcc.gnu.org/onlinedocs/gcc-4.1.1/gcc/Invoking-GCC.html#Invoking-GCC It might be useful to change that by adding links to the specific cases where this is false, maybe in footnote style "[1], [2]". Given the way -l works, I can't imagine a way to improve the error diagnostics to show this mistake up. so the only outstanding question for me is whether there is a tool to sort of list of libraris into the correct order for addition to a GCC command line? Thank you Hugh
