Re: [avr-gcc-list] EF_AVR_LINKRELAX_PREPARED bit in e_flags

[Joerg Wunsch]

In article <address@hidden> you write:

>Rarely do one set of modules, compiled with one set of
>compiler flags, get linked to another set of modules, compiled with a
>different, incompatible set of compiler flags.

As Johann already pointed out, avr-libc is compiled with default C
flags (i.e. none of those -m or -f options beyond -mmcu is applied).
Now, if you look into the Internet, the compile-time options there are
full of -f and -m stuff (including, but not limited to, the Mfile
template, the WinAVR Makefile template, and Atmel Studio generated
code).  Consequently, there's a clash between any these object
modules, and avr-libc itself.

As most projects link against avr-libc, they are always at risk.

>If we start including those compiler flags, where does it end? How
>many should we include and check for?

Only those that affect the ABI.  Johann mentioned them.

Of course, it would have been nice if people wouldn't have started
using these ABI-incompatibility options in the first place, but they
do.  Yes, I'm partially guilty for spreading them around :) by not
thoroughly thinking about what has once been distributed with Mfile.
I feel quite sorry for that.

We might perhaps concentrate on the more severe of those flags (-mint8
[cough, cough] and -fshort-enums immediately come to mind, as they
affect the size of certain objects).
-- 
cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)