The transparent_union variable attribute,
attached to a function parameter that is a union, means that the
corresponding argument can have the type of any union member, but
the argument is passed as if its type were that of the first union
member.
Note
The C specification states that the value returned when a
union is written as one type and read back with another is undefined.
Therefore, a method of distinguishing which type a transparent_union is
written in must also be passed as an argument.
Note
This variable attribute is a GNU compiler extension that is supported by the ARM compiler.
Note
You can also use this attribute on a typedef for
a union data type. In this case it applies to all function parameters
with that type.
Mode
typedef union
{
int myint;
float myfloat;
} transparent_union_t;
void Variable_Attributes_transparent_union_0(transparent_union_t aUnion __attribute__ ((transparent_union)))
{
static int aStatic;
aStatic +=aUnion.myint;
}
void Variable_Attributes_transparent_union_1()
{
int aLocal =0;
float bLocal =0;
Variable_Attributes_transparent_union_0(aLocal);
Variable_Attributes_transparent_union_0(bLocal);
}
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