URL:
<http://savannah.nongnu.org/bugs/?36124>
Summary: Improve documentation on .bss clear when used in
assembler
Project: AVR C Runtime Library
Submitted by: wek
Submitted on: Sat 07 Apr 2012 02:02:23 PM GMT
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: Any
Fixed Release: None
_______________________________________________________
Details:
Newer builds of the avr-gcc toolchain, such as WinAVR20100110, or builds
including the PR18145 fixup (4.7+), contain a patch which results in
conditional linking of the .bss cleanup loop only if it is needed for the C
source (similarly for the initialized .data). This may lead to surprising
behaviour when such variables are defined only in assembler parts of a
project.
It is therefore suggested to add something like the following text to
http://www.nongnu.org/avr-libc/user-manual/assembler.html after "For devices
that have RAM, initializing the RAM variables can also be utilized.", or
http://www.nongnu.org/avr-libc/user-manual/mem_sections.html#sec_dot_init into
the chapters dealing with .data and .bss sections, or both as appropriate:
Note: To ensure that variables in .bss section are zeroed upon startup, add
the following line to the assembler source:
.global __do_clear_bss
To ensure that variables in .data section are initialized from FLASH during
startup, add the following line to the assembler source:
.global __do_copy_data
(This submission is result of discussion on AVRFreaks
http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=119131&highlight=
)
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