Using the generic marshaller has drawbacks beyond performance. One such
drawback is that it breaks the stack unwinding from the Linux kernel due
to having unsufficient data to walk past ffi_call_unixt64. That means that
performance profiling by application developers looks grouped among
seemingly unrelated code paths.
While we can't fix the kernel unwinding here, we can provide proper
c_marshallers and va_marshallers for objects within Gio so that
performance profiling of applications is more reliable.
Related to GNOME/Initiatives#10
If c_marshaller is provided during g_signal_new() registration, the
automatic va_marshaller will not be set. If we leave the c_marshaller as
NULL in the simple cases, both a c_marshaller and va_marshaller will be
set for us.
This is particularly helpful when dealing with stack traces from Linux
perf, which often cannot unwind the stack beyond the ffi_call_unix64
stack-frame on x86_64.
Related to GNOME/Initiatives#10
To help cross compilation, don't use glib-genmarshal in our
build. This is easy now that we have g_cclosure_marshal_generic().
In gobject/, add gmarshal.[ch] to git (making the existing entry
points stubs).
In gio/, simply switch to using g_cclosure_marshal_generic().
https://bugzilla.gnome.org/show_bug.cgi?id=652168
