[ECOS] printf problem in twothreads sample

[Jonathan Larmour]

Rod Campbell wrote:
> 
> Thanks for the reply.  I looked at the assembler code and I see no
> problem with it that should result in an illegal instruction exception. 
> I then changed to use a version of redboot that I created for startup
> debugging - it has some extra assembler code at the various exception
> vectors that wiggle some unused processor port pins to communicate
> exception data to a logic analyzer.  
> 
> When I loaded Twothreads.c and single-stepped, my logic analyzer
> captured the TRAP exception that GDB/redboot sets for this purpose (as
> expected).  But when I got to the point where vfnprintf() has its
> problems (when processing the "%" in the format string), instead of
> getting the SIGILL, the debugger just stopped responding and I saw the
> same stream of ascii zeros sent to the debug console window as before. 
> The logic analyzer did not trigger - which means there was no exception
> during this time.  
> 
> Since I was using a modified redboot, the locations of various routines
> had possibly changed from my previos tests.  I wonder if there is a bad
> pointer somewhere in the code shared between RedBoot and my app -
> possibly related to the VVT?  

Maybe memory could have gotten corrupted somehow. Have you actually 
disassembled the contents of memory at the point of the SIGILL using GDB? 
Does it SIGILL at the same place each time?

I'd also try compiling without optimization, just in case (and do be sure 
the compiler is being invoked with -m3, not -m4 or -m4-nofpu) since your 
board is an SH3 I believe.

> I also came across a previous post in this archive - "printf in
> Redboot/GDB" of 10 Oct 2002, where Gary Thomas states that "printf()
> uses higher level functionality which is not enabled in the simple
> ROM-based RedBoot" (and I AM using a ROM-based Redboot).  However my
> symptoms differ from that post - printf DOES work for me if the data is
> static.  Is Gary's statement true for my case?  I don't want to ignore a
> problem that may be a symptom of a larger problem.  Thanks. 

He meant using printf *in* RedBoot, as opposed to in an application loaded 
by RedBoot.

Jifl
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