Zilog Z8F0130 - Manual (Page 244)

Using the ANSI C-Compiler UM013037-1212
220
Zilog Developer Studio II – Z8 Encore!
User Manual
Return Value
The compiler places the return values of a function in the registers listed in Table 46.
For functions returning an aggregate, see the Special Cases section below for details about
how they are returned.
Special Cases
Some function calls do not follow the mechanism described in the Function Call Mecha-
nism: Dynamic Frame section on page 215. Such cases are described in the following sec-
tions:
•
Returning Structure – see page 220
•
Not Allocating a Local Frame – see page 220
Returning Structure
If the function returns a structure, the caller allocates the space for the structure and then
passes the address of the return space to the called function as an additional and first argu-
ment. To return a structure, the called function then copies the structure to the memory
block pointed to by this argument.
Not Allocating a Local Frame
The compiler does not allocate a local frame for a function in the following case:
•
The function does not have any local stack variables, stack arguments, or compiler-
generated temporaries.
Table 46. Return Value Registers
Return Type
Return Value
Registers
char R0
short R0,R1
int R0,R1
long R0,R1,R2,R3
float R0,R1,R2,R3
double R0,R1,R2,R3
near * R0
far * R0,R1
rom * R0,R1