Steam's gameoverlayrenderer.so relies on libX11 symbols to be available
without actually loading that library directly. This works on an unthunked
system since libGL.so depends on libGLX.so, which in turn pulls in libX11.so
at load-time. Adding a fake libX11 dependency to the libGL-guest thunks
reproduces this behavior.
This function must be able to handle both guest heap pointers *and* host heap
pointers, so it only forwards to the native host library for the latter.
This is because Xlibint users allocate memory using internal macros aliasing
to libc's malloc but then they free using the function XFree. For libX11,
this is not a problem since the allocation happens in a thunked API function
(and hence on the host heap), but if a function from an unthunked library
accesses Xlibint, it will allocate on the guest heap.
One notable example where this was encountered is XF86VidModeGetAllModeLines.
Makes it print to stderr instead of stdout.
Also sets the mutex symbols to something that can be debugged.
Found something linking to them but not actually using them.
Ryan Houdek