URL:
<http://savannah.nongnu.org/bugs/?49567>
Summary: Use meta-info from --print-multi-lib and
--print-multi-directory
Project: AVR C Runtime Library
Submitted by: gjlayde
Submitted on: Wed 09 Nov 2016 02:32:38 PM GMT
Category: Build Infrastructure
Severity: 3 - Normal
Priority: 5 - Normal
Item Group: Build system
Status: None
Percent Complete: 0%
Assigned to: None
Originator Email:
Open/Closed: Open
Discussion Lock: Any
Release: 2.0.0
Fixed Release: None
_______________________________________________________
Details:
Currently, all the multilib layout and device -> multilib mapping and multilib
-> options mapping is hand coded in scripts like devtools/gen-avr-lib-tree.sh
avr-gcc is able to provide information about the multilib layout. Using this
feature can be used to dynamically adjust avr-libc build machinery to the
actual multilib layout implemented by avr-gcc.
* Left of ";" you see the relative path where the files belonging to
respective multilib variant will be situated.
* Right of ";" are the options ("@" stands for " -") to select that multilib)
$ avr-gcc --print-multi-lib
.;
avr25;@mmcu=avr25
avr3;@mmcu=avr3
avr31;@mmcu=avr31
avr35;@mmcu=avr35
avr4;@mmcu=avr4
avr5;@mmcu=avr5
avr51;@mmcu=avr51
avr6;@mmcu=avr6
avrxmega2;@mmcu=avrxmega2
avrxmega4;@mmcu=avrxmega4
avrxmega5;@mmcu=avrxmega5
avrxmega6;@mmcu=avrxmega6
avrxmega7;@mmcu=avrxmega7
avrtiny;@mmcu=avrtiny
tiny-stack;@msp8
avr25/tiny-stack;@mmcu=avr25@msp8
Notice how -msp8 is required to select "tiny-stack" (and *not* -mtiny-stack)
which cause quite some confusion in the past.
In order to find out in which multilib a specific device is located, there is
$ avr-gcc -mmcu=at43usb320 --print-multi-directory
avr31
$ avr-gcc -mmcu=attiny261 --print-multi-directory
avr25/tiny-stack
The advantage of factoring out multilib layout is obvious. Suppose there is
some avr-gcc flaw like http://gcc.gnu.org/PR78275 aka.
https://savannah.nongnu.org/bugs/index.php?49565
If meta information from the compiler driver was used, there wouldn't have
been a need to file a libc bug for a wrong multilib for AT43usb320 because
avr-libc would factor out the multilib location and draw that information from
avr-gcc.
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