glib/docs/reference/gobject/value-collection.md

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Title: Value Collection
SPDX-License-Identifier: LGPL-2.1-or-later
SPDX-FileCopyrightText: 2005 Matthias Clasen
# Value Collection
GLib provides a set of macros for the varargs parsing support needed
in variadic GObject functions such as [ctor@GObject.Object.new] or
[method@GObject.Object.set]
They currently support the collection of integral types, floating point
types and pointers.
## Macros
`G_VALUE_COLLECT_INIT(value, _value_type, var_args, flags, __error)`
: Collects a variable argument value from a `va_list`.
We have to implement the varargs collection as a macro, because on some
systems `va_list` variables cannot be passed by reference.
Since: 2.24
`G_VALUE_COLLECT_INIT2(value, g_vci_vtab, _value_type, var_args, flags, __error)`
: A variant of `G_VALUE_COLLECT_INIT` that provides the [struct@GObject.TypeValueTable]
to the caller.
Since: 2.74
`G_VALUE_COLLECT(value, var_args, flags, __error)`
: Collects a variable argument value from a `va_list`.
We have to implement the varargs collection as a macro, because on some systems
`va_list` variables cannot be passed by reference.
Note: If you are creating the `value argument` just before calling this macro,
you should use the `G_VALUE_COLLECT_INIT` variant and pass the uninitialized
`GValue`. That variant is faster than `G_VALUE_COLLECT`.
`G_VALUE_COLLECT_SKIP(_value_type, var_args)`
: Skip an argument of type `_value_type` from `var_args`.
`G_VALUE_LCOPY(value, var_args, flags, __error)`
: Stores a values value into one or more argument locations from a `va_list`.
This is the inverse of G_VALUE_COLLECT().
`G_VALUE_COLLECT_FORMAT_MAX_LENGTH`
: The maximal number of [type@GObject.TypeCValue]s which can be collected for a
single `GValue`.