Use of -Werror in systemtap Module Makefiles

[David Wilder <dwilder at us dot ibm dot com>]

I am testing stap on SLES10 s390, and have run into the following issue:

We are using -Werror in the tap modules Makefile causing the following 
error during module builds.
[...]
cc1: warnings being treated as errors
/usr/local/share/systemtap/runtime/vsprintf.c: In function '_stp_vsnprintf':
/usr/local/share/systemtap/runtime/vsprintf.c:428: warning: frame size 
of '_stp_vsnprintf' is 256 bytes
make[1]: *** [/tmp/stapKvDWR6/stap_31450.o] Error 1
make: *** [_module_/tmp/stapKvDWR6] Error 2

Using -Werror causes the warning to be treated as errors so the module 
build fails.
The SUSE kernel config has CONFIG_WARN_STACK_SIZE=256 that get used by 
the Makefile as so:
-mwarn-framesize=$(CONFIG_WARN_STACK_SIZE)

I could argue that SUSE's config needs to change, but is that the right 
thing to do?   Should systemtap be dependent on a distros config (other 
than CONFIG_KPROBES)?  Should -Werror be removed from the systemtap 
module build?

A related issue:
I also get the following warning (treated and as an error)
[...]
/usr/local/share/systemtap/runtime/stack.c: In function 
'_stp_stack_sprintj':
/usr/local/share/systemtap/runtime/stack.c:338: warning: 'stack' may be 
used uninitialized in this function 
[...]

In this case the uninitialized value wont cause a problem as "stack" is 
only passed as a pointer to another function to return a value in.  I 
don't see the error on i386 so I am assuming some gcc option in the SUSE 
S390 kernel Makefile causes the warning (I am not sure what option 
yet).  It is easy to fix by initializing "stack" but again should a 
distros kernel Makefiles cause systemtap module builds to fail?

Comments? Suggestions?

--
David Wilder
IBM Linux Technology Center
Beaverton, Oregon, USA 
dwilder@us.ibm.com
(503)578-3789