GObject Reference Manual: Varargs Value Collection

## Varargs Value Collection Varargs Value Collection — Converting varargs to generic values |

## Functions

#define | G_VALUE_COLLECT_INIT()
#define | G_VALUE_COLLECT()
#define | G_VALUE_COLLECT_SKIP()
#define | G_VALUE_LCOPY()

## Types and Values

union | GTypeCValue
#define | G_VALUE_COLLECT_FORMAT_MAX_LENGTH

## Includes

    #include <glib-object.h>
    #include <gobject/gvaluecollector.h>

## Description

The macros in this section provide the varargs parsing support needed in variadic GObject functions such as `g_object_new()` or `g_object_set()`. They currently support the collection of integral types, floating point types and pointers.

## Functions

### G_VALUE_COLLECT_INIT()

    #define             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.

#### Parameters

value | a GValue return location. `value` must contain only 0 bytes. |
_value_type | the GType to use for `value` . |
var_args | the va_list variable; it may be evaluated multiple times |
flags | flags which are passed on to the `collect_value()` function of the GTypeValueTable of `value` . |
__error | a gchar** variable that will be modified to hold a `g_new()` allocated error messages if something fails |

Since 2.24

### G_VALUE_COLLECT()

    #define             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 unitialized GValue. That variant is faster than G_VALUE_COLLECT.

#### Parameters

value | a GValue return location. `value` is supposed to be initialized according to the value type to be collected |
var_args | the va_list variable; it may be evaluated multiple times |
flags | flags which are passed on to the `collect_value()` function of the GTypeValueTable of `value` . |
__error | a gchar** variable that will be modified to hold a `g_new()` allocated error messages if something fails |

### G_VALUE_COLLECT_SKIP()

    #define             G_VALUE_COLLECT_SKIP(_value_type, var_args)

### G_VALUE_LCOPY()

    #define             G_VALUE_LCOPY(value, var_args, flags, __error)

Collects a value's variable argument locations from a va_list. Usage is analogous to `G_VALUE_COLLECT()`.

#### Parameters

value | a GValue return location. `value` is supposed to be initialized according to the value type to be collected |
var_args | the va_list variable; it may be evaluated multiple times |
flags | flags which are passed on to the `lcopy_value()` function of the GTypeValueTable of `value` . |
__error | a gchar** variable that will be modified to hold a `g_new()` allocated error messages if something fails |

## Types and Values

### union GTypeCValue

A union holding one collected value.

#### Members

gint `v_int`; | the field for holding integer values |
glong `v_long`; | the field for holding long integer values |
gint64 `v_int64`; | the field for holding 64 bit integer values |
gdouble `v_double`; | the field for holding floating point values |
gpointer `v_pointer`; | the field for holding pointers |

### G_VALUE_COLLECT_FORMAT_MAX_LENGTH

    #define G_VALUE_COLLECT_FORMAT_MAX_LENGTH (8)

The maximal number of GTypeCValues which can be collected for a single GValue.