Re: [Qemu-devel] [PATCH 1/2] Add a DTrace tracing backend targetted for SystemTAP compatability

[Anthony Liguori <anthony@codemonkey.ws>]

On 11/16/2010 12:54 PM, Peter Maydell wrote:
> On 16 November 2010 18:10, Anthony Liguori<anthony@codemonkey.ws>  wrote:
>    
>> On 11/16/2010 11:43 AM, Peter Maydell wrote:
>>      
>>> Unfortunately these commits:
>>> 2834c3e Add support for generating a systemtap tapset static probes
>>> 4addb11 Add a DTrace tracing backend targetted for SystemTAP compatability
>>>        
>> What's your configure output?
>>      
> I've attached it; the trace related bits are:
> Trace backend     nop
> Trace output file trace-<pid>
>
>    
>> I don't have the right environment to build with systemtap support, but
>> --trace-backend=nop should work regardless.
>>      
> I'm using the nop backend, yes.
>
> I think the problem is that commit 2834c3e adds a target 'trace:' to the
> Makefile.target which looks like it's intended to be a phony target. However
> it isn't marked as such, so make actually tries to create a binary 'trace'
> by falling back to its default rules (since there's a "trace.c" in the root
> directory):
>
> petmay01@LinaroE102767:~/qemu-test/qemu/i386-softmmu$ make -n trace
> echo "  CC    trace.o"&&  gcc -I/home/petmay01/qemu-test/qemu/slirp
> -Werror -m64 -I. -I/home/petmay01/qemu-test/qemu -D_FORTIFY_SOURCE=2
> -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE
> -Wstrict-prototypes -Wredundant-decls -Wall -Wundef -Wendif-labels
> -Wwrite-strings -Wmissing-prototypes -fno-strict-aliasing
> -fstack-protector-all -Wempty-body -Wnested-externs -Wformat-security
> -Wformat-y2k -Winit-self -Wignored-qualifiers -Wold-style-declaration
> -Wold-style-definition -Wtype-limits -DHAS_AUDIO -DHAS_AUDIO_CHOICE
> -I/home/petmay01/qemu-test/qemu/fpu
> -I/home/petmay01/qemu-test/qemu/tcg
> -I/home/petmay01/qemu-test/qemu/tcg/i386  -DTARGET_PHYS_ADDR_BITS=32
> -I.. -I/home/petmay01/qemu-test/qemu/target-i386 -DNEED_CPU_H     -MMD
> -MP -MT trace.o -MF ./trace.d -O2 -g  -c -o trace.o
> /home/petmay01/qemu-test/qemu/trace.c
> echo "  LINK  trace"&&  gcc -I/home/petmay01/qemu-test/qemu/slirp
> -Werror -m64 -I. -I/home/petmay01/qemu-test/qemu -D_FORTIFY_SOURCE=2
> -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE
> -Wstrict-prototypes -Wredundant-decls -Wall -Wundef -Wendif-labels
> -Wwrite-strings -Wmissing-prototypes -fno-strict-aliasing
> -fstack-protector-all -Wempty-body -Wnested-externs -Wformat-security
> -Wformat-y2k -Winit-self -Wignored-qualifiers -Wold-style-declaration
> -Wold-style-definition -Wtype-limits -DHAS_AUDIO -DHAS_AUDIO_CHOICE
> -I/home/petmay01/qemu-test/qemu/fpu
> -I/home/petmay01/qemu-test/qemu/tcg
> -I/home/petmay01/qemu-test/qemu/tcg/i386  -DTARGET_PHYS_ADDR_BITS=32
> -I.. -I/home/petmay01/qemu-test/qemu/target-i386 -DNEED_CPU_H     -O2
> -g  -Wl,--warn-common -m64 -g   -o trace trace.o -lrt -lpthread
> -lutil -lcurl   -lncurses  -luuid -lpng -lsasl2 -lgnutls   -lSDL
> -lX11  -laio -lm -lz
>
> ...and linking only trace.o into a binary 'trace' fails because
> trace.c doesn't have a main() (or indeed any functions at all).
>
> If I add a ".PHONY: trace" or change the "trace" target
> name to "tracexyzzy" then this fixes the problem.
>    

Curious, care to send a patch?  I think I'm not seeing this because I 
build with srcdir != objdir.

Regards,

Anthony Liguori

> -- PMM
>