Problem to resolve "sqrt" symbol from shell/main_ping.c for lpc17xx_ea_ram BSP

[Chris Johns]

On 2/10/2014 11:57 am, Pavel Pisa wrote:
> Hello all,
>
> when have tested recent master branch (fbe59f7c6756edc2952b13167893b85fe6e7aecb)
> build configured for lpc17xx_ea_ram BSP, I am experiencing next error for my
> code with networking enabled. It seems to be related to add of ping command.
>
> Even addition of -lm to my LDFLAGS does not help
>
> GCC call from OMK based makefile
>
> arm-rtems4.11-gcc --pipe -B/opt/rtems4.11/arm-rtems4.11/lpc17xx_ea_ram/lib/ \
>    -specs bsp_specs -qrtems -march=armv7-m -mthumb \
>    -I /home/pi/repo/rtems/build/arm-lpc17xx_ea_ram/omk-template/_compiled/lpc17xx_ea_ram/include \
>    -Wall -O2 -g init.o task_1.o \
>    -L/home/pi/repo/rtems/build/arm-lpc17xx_ea_ram/omk-template/_compiled/lpc17xx_ea_ram/lib \
>    -lbar -lnfs -lm  -o /home/pi/repo/rtems/build/arm-lpc17xx_ea_ram/omk-template/_compiled/lpc17xx_ea_ram/bin/appnet
>
> Error reported
>
> /opt/rtems4.11/arm-rtems4.11/lpc17xx_ea_ram/lib/librtemscpu.a(libshell_a-main_ping.o): In function `g_finish':
> /home/pi/repo/rtems/build/arm-lpc17xx_ea_ram/rtems/arm-rtems4.11/c/lpc17xx_ea_ram/cpukit/libmisc/../../../../../../../../git/rtems/c/src/../../cpukit/libmisc/shell/main_ping.c:1642:
> undefined reference to `sqrt'
> collect2: error: ld returned 1 exit status
> make[3]: *** [/home/pi/repo/rtems/build/arm-lpc17xx_ea_ram/omk-template/_compiled/lpc17xx_ea_ram/bin/appnet] Error 1
> make[2]: *** [binary-pass-this-dir] Error 2
> make[1]: *** [binary-pass-appnet-subdir] Error 2
> make: *** [binary-pass] Error 2
>
> I have investigated how collect is called and even tried to modify it by adding libm.a
>
> /usr/arm-rtems4.11/gcc/4.9.1/bin/../libexec/gcc/arm-rtems4.11/4.9.1/collect2 \
>    -dc -dp -N -o /home/pi/repo/rtems/build/arm-lpc17xx_ea_ram/omk-template/_compiled/lpc17xx_ea_ram/bin/appnet \
>    /opt/rtems4.11/arm-rtems4.11/lpc17xx_ea_ram/lib/start.o \
>    /usr/arm-rtems4.11/gcc/4.9.1/bin/../lib/gcc/arm-rtems4.11/4.9.1/thumb/armv7-m/crti.o \
>    /usr/arm-rtems4.11/gcc/4.9.1/bin/../lib/gcc/arm-rtems4.11/4.9.1/thumb/armv7-m/crtbegin.o \
>    -e _start \
>    -L/home/pi/repo/rtems/build/arm-lpc17xx_ea_ram/omk-template/_compiled/lpc17xx_ea_ram/lib \
>    -L/usr/arm-rtems4.11/gcc/4.9.1/bin/../lib/gcc/arm-rtems4.11/4.9.1/thumb/armv7-m \
>    -L/usr/arm-rtems4.11/gcc/4.9.1/bin/../lib/gcc/arm-rtems4.11/4.9.1/../../../../arm-rtems4.11/lib/thumb/armv7-m \
>    -L/opt/rtems4.11/arm-rtems4.11/lpc17xx_ea_ram/lib -L/usr/arm-rtems4.11/gcc/4.9.1/bin/../lib/gcc/arm-rtems4.11/4.9.1 \
>    -L/usr/arm-rtems4.11/gcc/4.9.1/bin/../lib/gcc \
>    -L/usr/arm-rtems4.11/gcc/4.9.1/bin/../lib/gcc/arm-rtems4.11/4.9.1/../../../../arm-rtems4.11/lib \
>     init.o task_1.o -lbar -lnfs \
>     /usr/arm-rtems4.11/lib/thumb/armv7-m/libm.a \
>     --start-group -lgcc --start-group -lrtemsbsp -lrtemscpu -lc -lgcc --end-group \
>     -T /opt/rtems4.11/arm-rtems4.11/lpc17xx_ea_ram/lib/linkcmds --end-group \
>     /usr/arm-rtems4.11/gcc/4.9.1/bin/../lib/gcc/arm-rtems4.11/4.9.1/thumb/armv7-m/crtend.o \
>     /usr/arm-rtems4.11/gcc/4.9.1/bin/../lib/gcc/arm-rtems4.11/4.9.1/thumb/armv7-m/crtn.o
>
> What seems to be problem cause is the fact, that bsp_specs adds libraries
> group including librtemscpu.a after libm.a. Because libm.a is not in the group
> then repeated search for sqrt() is not run after ping inclussion.
> Adding libm at the end of manually crafted collect2 line helps
>
>     /usr/arm-rtems4.11/lib/thumb/armv7-m/libm.a
>
> Sequence of link specification
>
> %{qrtems: --start-group  -lrtemsbsp -lrtemscpu  -lc -lgcc --end-group %{!qn
>
> is compiled in GCC driver /usr/arm-rtems4.11/gcc/4.9.1/bin/gcc, which is
> defined in GCC sources
>
> gcc-4.9.1/gcc/config/rtems.h
>
> #undef LIB_SPEC
> #define LIB_SPEC "%{!qrtems: " STD_LIB_SPEC "} " \
> "%{!nostdlib: %{qrtems: --start-group \
>   -lrtemsbsp -lrtemscpu \
>   -lc -lgcc --end-group %{!qnolinkcmds: -T linkcmds%s}}}"
>
> If float funtions support is needed by rtems core libraries then
> "-lm" or "libm.a" has to be included in this define.
>

This is a great summary of the issue. We really cannot change this as it 
stands until after 4.11 is released.

> The problem is caused by "ping" statistic/standard deviation computation
> in there

It is and it was a mistake on my part. My zynq testing has a NEON and 
-lm was being linked so I was not aware of the issue.

>
> cpukit/libmisc/shell/main_ping.c:1642
>
> 	if (nreceived && timing) {
> 		double n = nreceived + nrepeats;
> 		double avg = tsum / n;
> 		double vari = tsumsq / n - avg * avg;
> 		(void)printf(
> 		    "round-trip min/avg/max/stddev = %.3f/%.3f/%.3f/%.3f ms\n",
> 		    tmin, avg, tmax, sqrt(vari));
> 	}
>
> I expect that problem can be hidden on hardware floating point
> targets because sqrt is inlined/translated directly to FPU
> instructions.
>
> If the politics is not to require/pull in FPU support for core
> libraries then I suggest to replace whole statistic computation
> by fixed point/fraction based code or at least use integer/long based
> sqrt replacement.

Or just remove the need for the stddev. Is it really needed ?

>
> May it be that problem is specific to my local toolchain build
> and makefiles used but my guess is that it is generic.
>

No it is not and it is on my list of things to clean up. There is 
another unrelated issue in the ping I also wanted to look at.

Chris