diff --git a/docs/glib-adoption.rst b/docs/glib-adoption.rst new file mode 100644 index 0000000000..62ddd7c61d --- /dev/null +++ b/docs/glib-adoption.rst @@ -0,0 +1,96 @@ +===================== +Adoption of GLib APIs +===================== + +Libvirt has adopted use of the `GLib +library `__. 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. + +The following is a list of libvirt APIs that should no longer be +used in new code, and their suggested GLib replacements: + +``VIR_ALLOC``, ``VIR_REALLOC``, ``VIR_RESIZE_N``, ``VIR_EXPAND_N``, ``VIR_SHRINK_N``, ``VIR_FREE``, ``VIR_APPEND_ELEMENT``, ``VIR_INSERT_ELEMENT``, ``VIR_DELETE_ELEMENT`` + Prefer the GLib APIs ``g_new0``/``g_renew``/ ``g_free`` in most + cases. There should rarely be a need to use + ``g_malloc``/``g_realloc``. Instead of using plain C arrays, it + is preferrable to use one of the GLib types, ``GArray``, + ``GPtrArray`` or ``GByteArray``. These all use a struct to + track the array memory and size together and efficiently + resize. **NEVER MIX** use of the classic libvirt memory + allocation APIs and GLib APIs within a single method. Keep the + style consistent, converting existing code to GLib style in a + separate, prior commit. +``virStrerror`` + The GLib ``g_strerror()`` function should be used instead, + which has a simpler calling convention as an added benefit. + +The following libvirt APIs have been deleted already: + +``VIR_AUTOPTR``, ``VIR_AUTOCLEAN``, ``VIR_AUTOFREE`` + The GLib macros ``g_autoptr``, ``g_auto`` and ``g_autofree`` + must be used instead in all new code. In existing code, the + GLib macros must never be mixed with libvirt macros within a + method, nor should they be mixed with ``VIR_FREE``. If + introducing GLib macros to an existing method, any use of + libvirt macros must be converted in an independent commit. +``VIR_DEFINE_AUTOPTR_FUNC``, ``VIR_DEFINE_AUTOCLEAN_FUNC`` + The GLib macros ``G_DEFINE_AUTOPTR_CLEANUP_FUNC`` and + ``G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC`` must be used in all new + code. Existing code should be converted to the new macros where + relevant. It is permissible to use ``g_autoptr``, ``g_auto`` on + an object whose cleanup function is declared with the libvirt + macros and vice-versa. +``VIR_AUTOUNREF`` + The GLib macros ``g_autoptr`` and + ``G_DEFINE_AUTOPTR_CLEANUP_FUNC`` should be used to manage + autoclean of virObject classes. This matches usage with GObject + classes. +``VIR_STRDUP``, ``VIR_STRNDUP`` + Prefer the GLib APIs ``g_strdup`` and ``g_strndup``. + ++-------------------------------+--------------------------------------+-------------------------------------------+ +| deleted version | GLib version | Notes | ++===============================+======================================+===========================================+ +| ``VIR_AUTOPTR`` | ``g_autoptr`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_AUTOCLEAN`` | ``g_auto`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_AUTOFREE`` | ``g_autofree`` | The GLib version does not use parentheses | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_AUTOUNREF`` | ``g_autoptr`` | The cleanup function needs to be defined | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_DEFINE_AUTOPTR_FUNC`` | ``G_DEFINE_AUTOPTR_CLEANUP_FUNC`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_DEFINE_AUTOCLEAN_FUNC`` | ``G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_STEAL_PTR`` | ``g_steal_pointer`` | ``a = f(&b)`` instead of ``f(a, b)`` | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_RETURN_PTR`` | ``return g_steal_pointer`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ARRAY_CARDINALITY`` | ``G_N_ELEMENTS`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_FALLTHROUGH`` | ``G_GNUC_FALLTHROUGH`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_FMT_PRINTF`` | ``G_GNUC_PRINTF`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_NOINLINE`` | ``G_GNUC_NO_INLINE`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_NORETURN`` | ``G_GNUC_NORETURN`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_RETURN_CHECK`` | ``G_GNUC_WARN_UNUSED_RESULT`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_SENTINEL`` | ``G_GNUC_NULL_TERMINATED`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_UNUSED`` | ``G_GNUC_UNUSED`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_STRDUP`` | ``g_strdup`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_STRNDUP`` | ``g_strndup`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``virStrerror`` | ``g_strerror`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ diff --git a/docs/hacking.rst b/docs/hacking.rst index 858dd2dfc1..cd009c4c73 100644 --- a/docs/hacking.rst +++ b/docs/hacking.rst @@ -74,4 +74,5 @@ you also take a look at the following documents: - `Programming languages `__ - `Developer tooling `__ - `Advanced test suite usage `__ +- `Adoption of GLib APIs `__ - `Committer guidelines `__