Is glib usable in an unobtrusive way?

The most obtrustive thing about glib is that any program or library using it is non-robust against resource exhaustion. It unconditionally calls abort when malloc fails and there's nothing you can do to fix this, as the entire library is designed around the concept that their internal allocation function g_malloc "can't fail"

As for the ugly "g" types, you definitely don't need any casts. The types are 100% equivalent to the standard types, and are basically just cruft from the early (mis)design of glib. Unfortunately the glib developers lack much understanding of C, as evidenced by this FAQ:

Why use g_print, g_malloc, g_strdup and fellow glib functions?

"Regarding g_malloc(), g_free() and siblings, these functions are much safer than their libc equivalents. For example, g_free() just returns if called with NULL.

(Source: https://developer.gnome.org/gtk-faq/stable/x908.html)

FYI, free(NULL) is perfectly valid C, and does the exact same thing: it just returns.

I have used GLib professionally for over 6 years, and have nothing but praise for it. It is very light-weight, with lots of great utilities like lists, hashtables, rand-functions, io-libraries, threads/mutexes/conditionals and even GObject. All done in a portable way. In fact, we have compiled the same GLib-code on Windows, OSX, Linux, Solaris, iOS, Android and Arm-Linux without any hiccups on the GLib side.

In terms of obtrusiveness, I have definitely "bought into the g", and there is no doubt in my mind that this has been extremely beneficial in producing stable, portable code at great speed. Maybe specially when it comes to writing advanced tests.

And if g_malloc don't suit your purpose, simply use malloc instead, which of course goes for all of it.