Re: [libvirt] [PATCH v2 02/23] build: link to glib library

Add the main glib.h to internal.h so that all common code can use it. Historically glib allowed applications to register an alternative memory allocator, so mixing g_malloc/g_free with malloc/free was not safe. This was feature was dropped in 2.46.0 with: commit 3be6ed60aa58095691bd697344765e715a327fc1 Author: Alexander Larsson <alexl(a)redhat.com&gt; Date: Sat Jun 27 18:38:42 2015 +0200 Deprecate and drop support for memory vtables Applications are still encourged to match g_malloc/g_free, but it is no longer a mandatory requirement for correctness, just stylistic. This is explicitly clarified in commit 1f24b36607bf708f037396014b2cdbc08d67b275 Author: Daniel P. Berrangé <berrange(a)redhat.com&gt; Date: Thu Sep 5 14:37:54 2019 +0100 gmem: clarify that g_malloc always uses the system allocator Applications can still use custom allocators in general, but they must do this by linking to a library that replaces the core malloc/free implemenentation entirely, instead of via a glib specific call. This means that libvirt does not need to be concerned about use of g_malloc/g_free causing an ABI change in the public libary, and can avoid memory copying when talking to external libraries. This patch probes for glib, which provides the foundation layer with a collection of data structures, helper APIs, and platform portability logic. Later patches will introduce linkage to gobject which provides the object type system, built on glib, and gio which providing objects for various interesting tasks, most notably including DBus client and server support and portable sockets APIs, but much more too. Reviewed-by: Pavel Hrdina <phrdina(a)redhat.com&gt; Signed-off-by: Daniel P. Berrangé <berrange(a)redhat.com&gt; --- docs/hacking.html.in | 21 +++++++++++++++++++++ src/Makefile.am | 2 ++ src/internal.h | 1 + src/lxc/Makefile.inc.am | 2 ++ src/remote/Makefile.inc.am | 1 + src/util/Makefile.inc.am | 1 + tests/Makefile.am | 3 ++- tools/Makefile.am | 1 + 8 files changed, 31 insertions(+), 1 deletion(-) diff --git a/docs/hacking.html.in b/docs/hacking.html.in index edf2f54ce3..93b451591e 100644 --- a/docs/hacking.html.in +++ b/docs/hacking.html.in @@ -989,6 +989,27 @@ BAD: it points to, or it is aliased to another pointer that is. </p> + <h2><a id="glib">Adoption of GLib APIs</a></h2> +

+ <p> + Libvirt has adopted use of the + <a href="https://developer.gnome.org/glib/stable/">GLib library</a>. + Due to libvirt's long history of development, there are many APIs + in libvirt, for which GLib provides an alternative solution. The + general rule to follow is that the standard GLib solution will be + preferred over historical libvirt APIs. Existing code will be + ported over to use GLib APIs over time, but new code should use + the GLib APIs straight away where possible. + </p> + + <p> + The following is a list of libvirt APIs that should no longer be + used in new code, and their suggested GLib replacements: + </p> + + <dl> + </dl> + <h2><a id="memalloc">Low level memory management</a></h2> <p>