URL:
<http://savannah.nongnu.org/bugs/?35240>
Summary: Incomplete Description of Calling Convention
Project: AVR C Runtime Library
Submitted by: dkinzer
Submitted on: Wed 04 Jan 2012 03:42:04 PM PST
Category: Documentation
Severity: 3 - Normal
Priority: 5 - Normal
Item Group: Documentation
Status: None
Percent Complete: 0%
Assigned to: None
Open/Closed: Open
Discussion Lock: Any
Release: 1.6.7
Fixed Release: None
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Details:
The avr-libc documentation section "11.14 What registers are used by the C
compiler?" is incomplete in that it does not describe the case where a
function returns a large (>64 bit) data item. As far as I can tell, in this
(perhaps unusual) case r25:24 contains a pointer to a buffer in which to
return the data and all parameters (if any) are shifted by two registers (i.e.
a first uint16_t parameter is in r23:22, etc.). Large pointer support may
change the register use in this case.
This observation applies to the documentation accompanying avr-libc v1.6.7 and
v1.8.0.
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