[yocto] libm implementation issue

[peterengcomau001 at adam.com.au]

 I have some software that uses specific mathematical functions. When
I attempt to compile them with the Yocto cross-compile tools, the
functions are not recognised. E.g. 'pow' in 
According to website
https://wiki.yoctoproject.org/wiki/Minimal_Image, not all eglibc
features are installed as standard, and that I should alter my
local.conf file I have added the following:

DISTRO_FEATURES_LIBC  += " libc-libm "
DISTRO_FEATURES_append = " ${DISTRO_FEATURES_LIBC} "

When I bitbake the image I get the following error: (this is just the
end of the error log - there are many undefined references)

|
/home/lachlan/poky/build-atmel/tmp/work/cortexa5t2hf-vfp-poky-linux-gnueabi/eglibc/2.19-r0/eglibc-2.19/libc/pwd/../nss/getXXbyYY_r.c:213:
undefined reference to `__nss_database_custom'
|
/home/lachlan/poky/build-atmel/tmp/work/cortexa5t2hf-vfp-poky-linux-gnueabi/eglibc/2.19-r0/build-arm-poky-linux-gnueabi/libc_pic.os:
In function `__getpwuid_r':
|
/home/lachlan/poky/build-atmel/tmp/work/cortexa5t2hf-vfp-poky-linux-gnueabi/eglibc/2.19-r0/eglibc-2.19/libc/pwd/../nss/getXXbyYY_r.c:196:
undefined reference to `__nscd_getpwuid_r'
|
/home/lachlan/poky/build-atmel/tmp/work/cortexa5t2hf-vfp-poky-linux-gnueabi/eglibc/2.19-r0/eglibc-2.19/libc/pwd/../nss/getXXbyYY_r.c:213:
undefined reference to `__nss_not_use_nscd_passwd'
|
/home/lachlan/poky/build-atmel/tmp/work/cortexa5t2hf-vfp-poky-linux-gnueabi/eglibc/2.19-r0/eglibc-2.19/libc/pwd/../nss/getXXbyYY_r.c:213:
undefined reference to `__nss_database_custom'
|
/home/lachlan/poky/build-atmel/tmp/sysroots/x86_64-linux/usr/libexec/cortexa5t2hf-vfp-poky-linux-gnueabi.gcc-cross-initial/gcc/arm-poky-linux-gnueabi/4.8.2/ld:
/home/lachlan/poky/build-atmel/tmp/work/cortexa5t2hf-vfp-poky-linux-gnueabi/eglibc/2.19-r0/build-arm-poky-linux-gnueabi/libc.so:
hidden symbol `__nss_not_use_nscd_group' isn't defined
|
/home/lachlan/poky/build-atmel/tmp/sysroots/x86_64-linux/usr/libexec/cortexa5t2hf-vfp-poky-linux-gnueabi.gcc-cross-initial/gcc/arm-poky-linux-gnueabi/4.8.2/ld:
final link failed: Bad value
| collect2: error: ld returned 1 exit status
| ERROR: Function failed: do_compile (log file is located at
/home/lachlan/poky/build-atmel/tmp/work/cortexa5t2hf-vfp-poky-linux-gnueabi/eglibc/2.19-r0/temp/log.do_compile.5266)
ERROR: Task 39
(/home/lachlan/poky/meta/recipes-core/eglibc/eglibc_2.19.bb,
do_compile) failed with exit code '1'

I have reviewed the sample.conf.extended file in the meta-yocto later
and the above code should be OK, except that I have added the '+' and
'append'. If I use DISTRO_FEATURES instead of DISTRO_FEATURES_append,
I get other errros:
Missing or unbuildable dependency chain was:
['packagegroup-base-wifi']
ERROR: Required build target 'atmel-qt5-demo-image' has no buildable
providers
Missing or unbuildable dependency chain was: ['atmel-qt5-demo-image',
'packagegroup-base-wifi']

If I use DISTRO_FEATURES_LIBC = instead of DISTRO_FEATURES_LIBC += ,
I get these errors:
ERROR: Unable to parse
/home/lachlan/poky/meta/recipes-core/packagegroups/packagegroup-core-boot.bb:
Exited with
"1"#                                                       
| ETA:  00:00:39
ERROR: Please ensure that your setting of
VIRTUAL-RUNTIME_init_manager (sysvinit) matches the entries enabled
in DISTRO_FEATURES

I am probably overriding a default setting Is there an alternative
way to include the libc-libm, or is there something else that could 
be causing the erro?

Thanks for any help

Lachlan
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