[En-Nut-Discussion] Just a word of warning with WinAVR-20050214.

Vesa Jääskeläinen chaac at nic.fi
Mon May 9 10:06:02 CEST 2005

Vesa Jääskeläinen wrote:
> Hi,
> I needed to disable all optimizations (-O0) when building Nut/OS to get 
> sample httpd application working correctly on ethernut 1.3g board. 
> Without disabling optimizations e1.3g wouldn't give response from 
> Ethernet interface.
> So if you are having strange problems with WinAVR and Nut/OS, try to 
> disable optimizations and see if that helps.
> I added "HWDEF += -O0" to UserConf.mk and rebuilt Nut/OS (make all & 
> make install)
> And then rebuilding test application and programming it to board I got 
> responses nicely from e1.3g.

I was able to trace it back to it's source. GCC is a bit too aggressive 
about optimizations, I really don't see its rationale but it optimized 
away NULL pointer checks in certain situations. I will continue 
discussion on this issue with GCC developers but following switch gives 
a cure "-fno-delete-null-pointer-checks".

I would propose this switch as a default compiler flag. Any objections?

In meanwhile when building Nut/OS you could use:

HWDEF += -fno-delete-null-pointer-checks

... in nut/UserConf.mk in build directory before issuing make all & make 

Problem code in a bit complex situation:
if ((ppv != NULL) && (*ppv != NULL)) {

First compare was omitted without this flag.

Vesa Jääskeläinen

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