Re: [XEN PATCH] tools/xenstore: mark variable in header as extern

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 20/05/2020 17:39, Anthony PERARD wrote:
> This patch fix "multiple definition of `xprintf'" (or xgt_handle)
> build error with GCC 10.1.0.
>
> These are the error reported:
>     gcc xs_tdb_dump.o utils.o tdb.o talloc.o      -o xs_tdb_dump
>     /usr/bin/ld: utils.o:./utils.h:27: multiple definition of `xprintf'; 
> xs_tdb_dump.o:./utils.h:27: first defined here
>     [...]
>     gcc xenstored_core.o xenstored_watch.o xenstored_domain.o 
> xenstored_transaction.o xenstored_control.o xs_lib.o talloc.o utils.o tdb.o 
> hashtable.o xenstored_posix.o      -lsystemd   -Wl,-rpath-link=... 
> ../libxc/libxenctrl.so -lrt  -o xenstored
>     /usr/bin/ld: xenstored_watch.o:./xenstored_core.h:207: multiple 
> definition of `xgt_handle'; xenstored_core.o:./xenstored_core.h:207: first 
> defined here
>     /usr/bin/ld: xenstored_domain.o:./xenstored_core.h:207: multiple 
> definition of `xgt_handle'; xenstored_core.o:./xenstored_core.h:207: first 
> defined here
>     /usr/bin/ld: xenstored_transaction.o:./xenstored_core.h:207: multiple 
> definition of `xgt_handle'; xenstored_core.o:./xenstored_core.h:207: first 
> defined here
>     /usr/bin/ld: xenstored_control.o:./xenstored_core.h:207: multiple 
> definition of `xgt_handle'; xenstored_core.o:./xenstored_core.h:207: first 
> defined here
>     /usr/bin/ld: xenstored_posix.o:./xenstored_core.h:207: multiple 
> definition of `xgt_handle'; xenstored_core.o:./xenstored_core.h:207: first 
> defined here
>
> A difference that I noticed with earlier version of the build chain is
> that before, I had:
>     $ nm xs_tdb_dump.o | grep xprintf
>     0000000000000008 C xprintf
> And now, it's:
>     0000000000000000 B xprintf
> With the patch apply, the symbol isn't in xs_tdb_dump.o anymore.
>
> Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>

Ah - this will be a side effect of defaulting to -fno-common now.

Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>