"Not Really Me" <scott@validatedQWERTYsoftware.XYZZY.com> wrote in message 
news:6r9q9gF5k0vU1@mid.individual.net...
> JeGy wrote:
>> Hi,
>>
>> does anyone here know
>> if the IAR AVR C-compiler sprintf() and associated functions
>> are thread safe in in multi-tasking, e.i. FreeRTOS?
>>
>> Regards
>>
>> Jens
>
> Sorry I didn't think of checking this when you first posted.  I checked 
> the source, none of the printf variants in the IAR libraries are thread 
> safe, this includes sprintf.

According to their AVR compiler documentation their sprintf() implementation 
is thread safe - so it is interesting if your inspection shows otherwise.

The FreeRTOS download includes a mini implementation of sprintf() that is 
thread safe.  I normally use that regardless as it uses much less stack than 
standard library variants.

-- 
Regards,
Richard.

+ http://www.FreeRTOS.org
Designed for microcontrollers.  More than 7000 downloads per month.

+ http://www.SafeRTOS.com
Certified by T&#4294967295;V as meeting the requirements for safety related systems.

JeGy wrote:
> Hi,
>
> does anyone here know
> if the IAR AVR C-compiler sprintf() and associated functions
> are thread safe in in multi-tasking, e.i. FreeRTOS?
>
> Regards
>
> Jens

Sorry I didn't think of checking this when you first posted.  I checked the 
source, none of the printf variants in the IAR libraries are thread safe, 
this includes sprintf.

-- 
Scott

Hi everybody,


Thanks for your answers and comments, is is good to know that one have 
friends out there when problems arise.

I am sorry that the subject was misleading, and I was not aware of the 
significant differences between sprintf and printf.

However, I have made my own thread safe sprintf function, and the embedded 
software now runs perfect.

So the conclusion is, that in this specific case, the sprintf was not thread 
safe

Best regards and a Happy Christmas

Jens

"JeGy" <gydesen.jensREMOVE@THISgmail.com> skrev i en meddelelse 
news:494a786d$0$15873$edfadb0f@dtext01.news.tele.dk...
> Hi,
>
> does anyone here know
> if the IAR AVR C-compiler sprintf() and associated functions
> are thread safe in in multi-tasking, e.i. FreeRTOS?
>
> Regards
>
> Jens
> 

bastian42@yahoo.com (42Bastian Schick) writes:

> On Fri, 19 Dec 2008 09:50:58 PST,
> mojaveg@mojaveg.lsan.mdsg-pacwest.com (Everett M. Greene) wrote:
>

[...]

>
> I don't think fprintf() is any better than printf(). 
> Actually the printf()/fprintf() function itself are maybe threadsafe
> (neglecting the errno), but the underlying I/O is not thread-safe with
> respect to single characters.
>
> I haven't seen a (f)printf() implementation which uses static
> variables, so the function is thread-safe.

There are implementations of floating point math that are not
thread-safe... so there must certainly also be printf ones too!

-- 

John Devereux

On Fri, 19 Dec 2008 09:50:58 PST,
mojaveg@mojaveg.lsan.mdsg-pacwest.com (Everett M. Greene) wrote:

>Tim Wescott <tim@seemywebsite.com> writes:
>> On Thu, 18 Dec 2008 17:21:07 +0100, JeGy wrote:
>> 
>> > does anyone here know
>> > if the IAR AVR C-compiler sprintf() and associated functions are thread
>> > safe in in multi-tasking, e.i. FreeRTOS?
>> > 
>> > Regards
>> > 
>> > Jens
>> 
>> At a top level, printf isn't really thread safe, at least to the extent 
>> that you cannot use printf in a lot of otherwise acceptable ways that 
>> don't end up with mangled printout.  Why?  Because if thread A prints out 
>> "How do I love you?", then thread B prints out "Toilet Clogged!!\n", then 
>> thread A prints out "  Let me count the ways.\n", each thread will be 
>> using printf "acceptably", yet the output will be puzzling, at best.
>> 
>> So were I developing a library, I wouldn't have a great deal of 
>> motivation to make printf thread safe (fprintf, OTOH, should be thread 
>> safe for any individual file).
>
>How is it that one variant of printf() can be "thread-safe"
>when another isn't?  They're all the same except for the
>destination of the result.

I don't think fprintf() is any better than printf(). 
Actually the printf()/fprintf() function itself are maybe threadsafe
(neglecting the errno), but the underlying I/O is not thread-safe with
respect to single characters.

I haven't seen a (f)printf() implementation which uses static
variables, so the function is thread-safe.
-- 
42Bastian
Do not email to bastian42@yahoo.com, it's a spam-only account :-)
Use <same-name>@monlynx.de instead !

Tim Wescott wrote:

> I'm not saying that it would be hard to _do_; my point is that printf is 
> designed with the underlying assumption that there is one data source 
> that is printing to one data sink, and so there is nothing in the 'normal 
> usage' of printf that makes its usage inherently thread safe.  If you 
> want to print messages to a common output (such as logging or what not), 
> then you need to package those messages up as whole entities and send 
> them, so they don't get scrambed up with one another.  Printf is simply 
> not suited to provide that functionality.

Unless stated explicitly, *.printf functions should not be assumed to be 
thread safe. Reason: format conversions and i/o errors modify the global 
variables such as errno. If the local thread storage is supported in the 
stddio library and by the OS, then *.printf functions are safe.

However it is not a big deal to protect *.printf by a semaphore anyway.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

Tim Wescott <tim@seemywebsite.com> writes:
> On Thu, 18 Dec 2008 17:21:07 +0100, JeGy wrote:
> 
> > does anyone here know
> > if the IAR AVR C-compiler sprintf() and associated functions are thread
> > safe in in multi-tasking, e.i. FreeRTOS?
> > 
> > Regards
> > 
> > Jens
> 
> At a top level, printf isn't really thread safe, at least to the extent 
> that you cannot use printf in a lot of otherwise acceptable ways that 
> don't end up with mangled printout.  Why?  Because if thread A prints out 
> "How do I love you?", then thread B prints out "Toilet Clogged!!\n", then 
> thread A prints out "  Let me count the ways.\n", each thread will be 
> using printf "acceptably", yet the output will be puzzling, at best.
> 
> So were I developing a library, I wouldn't have a great deal of 
> motivation to make printf thread safe (fprintf, OTOH, should be thread 
> safe for any individual file).

How is it that one variant of printf() can be "thread-safe"
when another isn't?  They're all the same except for the
destination of the result.

On Fri, 19 Dec 2008 03:36:27 -0800, vladitx wrote:

> The OP asked about "sprintf()", although the thread subject is
> misleading.

I was distracted by the title, and missed that essential point.  You 
would certainly want sprintf to be thread safe!

> If that's the case, "sprintf()" may well be thread-safe according to the
> answer of Richard.
> 
> Thread-safe "printf()" is not hard to do with the usual ring buffer, and
> with enough buffer size the calls won't be blocking more than the
> formatting time. But for AVR this is overkill.

I'm not saying that it would be hard to _do_; my point is that printf is 
designed with the underlying assumption that there is one data source 
that is printing to one data sink, and so there is nothing in the 'normal 
usage' of printf that makes its usage inherently thread safe.  If you 
want to print messages to a common output (such as logging or what not), 
then you need to package those messages up as whole entities and send 
them, so they don't get scrambed up with one another.  Printf is simply 
not suited to provide that functionality.

-- 
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

The OP asked about "sprintf()", although the thread subject is
misleading.

If that's the case, "sprintf()" may well be thread-safe according to
the answer of Richard.

Thread-safe "printf()" is not hard to do with the usual ring buffer,
and with enough buffer size the calls won't be blocking more than the
formatting time. But for AVR this is overkill.

On Thu, 18 Dec 2008 17:21:07 +0100, JeGy wrote:

> Hi,
> 
> does anyone here know
> if the IAR AVR C-compiler sprintf() and associated functions are thread
> safe in in multi-tasking, e.i. FreeRTOS?
> 
> Regards
> 
> Jens

At a top level, printf isn't really thread safe, at least to the extent 
that you cannot use printf in a lot of otherwise acceptable ways that 
don't end up with mangled printout.  Why?  Because if thread A prints out 
"How do I love you?", then thread B prints out "Toilet Clogged!!\n", then 
thread A prints out "  Let me count the ways.\n", each thread will be 
using printf "acceptably", yet the output will be puzzling, at best.

So were I developing a library, I wouldn't have a great deal of 
motivation to make printf thread safe (fprintf, OTOH, should be thread 
safe for any individual file).

-- 
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html