RealView Compilation Tools Compiler Reference Guide - ARM ...

Compiler-specific Features
Where:
return-type
is the type of a structure of up to four words in size.
Usage
Declaring a function __value_in_regs can be useful when calling functions that return
more than one result.
Restrictions
A C++ function cannot return a __value_in_regs structure if the structure requires copy
constructing.
If a virtual function declared as __value_in_regs is to be overridden, the overriding
function must also be declared as __value_in_regs. If the functions do not match, the
compiler generates an error.
Errors
Where the structure returned in a function qualified by __value_in_regs is too big, a
warning is produced and the __value_in_regs structure is then ignored.
Example
typedef struct int64_struct
{
unsigned int lo;
unsigned int hi;
} int64_struct;
__value_in_regs extern
int64_struct mul64(unsigned a, unsigned b);
See also
• __value_in_regs on page 4-14 in the Compiler User Guide.
4.1.19 __weak
This keyword instructs the compiler to export symbols weakly.
The __weak keyword can be applied to function and variable declarations, and to
function definitions.
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