• Fam Zheng's avatar
    rules.mak: Fix DSO build by pulling in archive symbols · c261d774
    Fam Zheng authored
    
    
    This fixes an issue with module build system. block/iscsi.so is
    currently broken:
    
        $ ~/build/last/qemu-img
        Failed to open module: /home/fam/build/master/block-iscsi.so:
        undefined symbol: qmp_query_uuid
        qemu-img: Not enough arguments
        Try 'qemu-img --help' for more information
    
    To fix this, we should (at least) let qemu-img link qmp_query_uuid from
    libqemustub.a. (There are a few other symbols missing, as well.)
    
    This patch changes the linking rules to:
    
    1) Build ".mo" with "ld -r -o $@ $^" for each ".so", and later build .so
       with it.
    
    2) Always build all the .mo before linking the executables. This is
       achieved by adding those .mo files to the executables' "-y"
       variables.
    
    3) When linking an executable, those .mo files in its "-y" variables are
       filtered out, and replaced by one or more -Wl,-u,$symbol flags. This
       is done in the added macro "process-archive-undefs".
    
       These "-Wl,-u,$symbol" flags will force ld to pull in the function
       definition from the archives when linking.
    
       Note that the .mo objects, that are actually meant to be linked in
       the executables, are already expanded in unnest-vars, before the
       linking command. So we are safe to simply filter out .mo for the
       purpose of pulling undefined symbols.
    
       process-archive-undefs works as this: For each ".mo", find all the
       undefined symbols in it, filter ones that are defined in the
       archives. For each of these symbols, generate a "-Wl,-u,$symbol" in
       the link command, and put them before archive names in the command
       line.
    
    Suggested-by: default avatarH.J. Lu <hjl.tools@gmail.com>
    Signed-off-by: default avatarFam Zheng <famz@redhat.com>
    Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    c261d774