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>

2 files changed, 14 insertions, 2 deletions

diff --git a/src/util/atom.c b/src/util/atom.c
index 37811f9..5f7f1c6 100644
--- a/src/util/atom.c
+++ b/src/util/atom.c
@@ -158,6 +158,8 @@ MakeAtom(const char *string, unsigned len, int makeit)
     int		h = 0;
     int		r;
 
+    OVERRIDE_SYMBOL(MakeAtom, string, len, makeit);
+
     hash = Hash (string, len);
     if (hashTable)
     {
@@ -230,6 +232,7 @@ MakeAtom(const char *string, unsigned len, int makeit)
 weak int
 ValidAtom(Atom atom)
 {
+    OVERRIDE_SYMBOL(ValidAtom, atom);
     return (atom != None) && (atom <= lastAtom);
 }
 
@@ -240,6 +243,7 @@ ValidAtom(Atom atom)
 weak char *
 NameForAtom(Atom atom)
 {
+    OVERRIDE_SYMBOL(NameForAtom, atom);
     if (atom != None && atom <= lastAtom)
 	return reverseMap[atom]->name;
     return NULL;
diff --git a/src/util/miscutil.c b/src/util/miscutil.c
index 3d802d2..61c9d11 100644
--- a/src/util/miscutil.c
+++ b/src/util/miscutil.c
@@ -45,14 +45,22 @@ from The Open Group.
 
 extern void BuiltinRegisterFpeFunctions(void);
 
-#ifndef NO_WEAK_SYMBOLS
 /* make sure everything initializes themselves at least once */
 weak unsigned long serverGeneration = 1;
-#endif
+
+unsigned long __GetServerGeneration (void);
+
+unsigned long
+__GetServerGeneration (void)
+{
+  OVERRIDE_DATA(serverGeneration);
+  return serverGeneration;
+}
 
 weak void
 register_fpe_functions (void)
 {
+    OVERRIDE_SYMBOL(register_fpe_functions);
     BuiltinRegisterFpeFunctions();
     FontFileRegisterFpeFunctions();
 #ifdef XFONT_FC