Make shared library work on Cygwin/MinGW

Weak symbols on PE platforms do not work the same way as on ELF
platforms, hence we have been unable to have a fully functional shared
libXfont until now.  This patch works around these issues so that we
can fix that.

In summary, only when compiling shared libraries on NO_WEAK_SYMBOLS
platforms, when the first stub is called, the invoking program is first
checked to determine if it exports the stubbed functions.  Then, for
every stub call, if the function is exported by the loader, it is called
instead of the stub code.

serverClient and serverGeneration are data pointers, and therefore are
replaced by getter functions. ErrorF is variadic, so the override is
routed through VErrorF instead. FatalError has no va_list equivalent,
but it is not actually used in libXfont and therefore should be safe to
remove.

This requires all X servers to export their symbols, which requires
forthcoming patches for hw/xwin and xfs; the other xservers (including
tigervnc) already do this via LD_EXPORT_SYMBOLS_FLAG.

Signed-off-by: Yaakov Selkowitz <yselkowitz@users.sourceforge.net>
Reviewed-by: Colin Harrison <colin.harrison@virgin.net>
Acked-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Tested-by: Jeremy Huddleston Sequoia <jeremyhu@apple.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/stubs/errorf.c b/src/stubs/errorf.c
index fd32965..d2de6c6 100644
--- a/src/stubs/errorf.c
+++ b/src/stubs/errorf.c
@@ -10,4 +10,5 @@
 weak void
 ErrorF(const char *f, ...)
 {
+    OVERRIDE_VA_SYMBOL(VErrorF, f);
 }