package/iputils: patch ping to link against libm

ping fails to compile with uClibc based toolchains with the error

undefined reference to `__finite'

Add a patch to link ping against libm to resolve the math library function finite().

Note, this error is not seen with glibc based toolchains because finite seems to be resolved in both libm and libc.

Fixes:
http://autobuild.buildroot.net/results/08f7386f75c881bc582b338824f8ccd509b2921e/
http://autobuild.buildroot.net/results/5aeef61fbd399dd78dc72b9e7cce978e6f1f58b4/

A pull request has been sent to fix this issue upstream, see
https://github.com/iputils/iputils/pull/42

Signed-off-by Martin Bark <[email protected]>

Martin,

Quoted 10 lines · Martin Bark

ping fails to compile with uClibc based toolchains with the error

undefined reference to `__finite'

Add a patch to link ping against libm to resolve the math library function finite().

Note, this error is not seen with glibc based toolchains because finite seems to be resolved in both libm and libc.

Quoted 8 lines

Fixes:
http://autobuild.buildroot.net/results/08f7386f75c881bc582b338824f8ccd509b2921e/
http://autobuild.buildroot.net/results/5aeef61fbd399dd78dc72b9e7cce978e6f1f58b4/

A pull request has been sent to fix this issue upstream, see
https://github.com/iputils/iputils/pull/42

Signed-off-by Martin Bark <[email protected]>

Thanks for working on this issue. However, I am not entirely happy with the explanation.

Indeed, if you try to build iputils against uClibc, it builds just fine. It is apparently only when the entire build is done with BR2_ENABLE_DEBUG=y that the build failure occurs. And your commit log doesn't explain at all why the problem only occurs when the build is done with debugging symbols enabled.

I've tried building iputils against uClibc, it works fine. I've tried building iputils against uClibc with BR2_ENABLE_DEBUG=y (using a pre-built uClibc toolchain, which isn't built with debugging symbols), and it works fine. So it seems that it only happens when the entire build is done with debugging symbols, including uClibc itself.

While linking with -lm might be the correct fix, I am not convinced yet due the lack of explanation for the root of the problem.

Thanks!

Thomas

--
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

Martin,

Quoted 10 lines · Martin Bark

ping fails to compile with uClibc based toolchains with the error

undefined reference to `__finite'

Add a patch to link ping against libm to resolve the math library function finite().

Note, this error is not seen with glibc based toolchains because finite seems to be resolved in both libm and libc.

Quoted 8 lines

Fixes:
http://autobuild.buildroot.net/results/08f7386f75c881bc582b338824f8ccd509b2921e/
http://autobuild.buildroot.net/results/5aeef61fbd399dd78dc72b9e7cce978e6f1f58b4/

A pull request has been sent to fix this issue upstream, see
https://github.com/iputils/iputils/pull/42

Signed-off-by Martin Bark <[email protected]>

Thanks for working on this issue. However, I am not entirely happy with the explanation.

Indeed, if you try to build iputils against uClibc, it builds just fine. It is apparently only when the entire build is done with BR2_ENABLE_DEBUG=y that the build failure occurs. And your commit log doesn't explain at all why the problem only occurs when the build is done with debugging symbols enabled.

I've tried building iputils against uClibc, it works fine. I've tried building iputils against uClibc with BR2_ENABLE_DEBUG=y (using a pre-built uClibc toolchain, which isn't built with debugging symbols), and it works fine. So it seems that it only happens when the entire build is done with debugging symbols, including uClibc itself.

While linking with -lm might be the correct fix, I am not convinced yet due the lack of explanation for the root of the problem.

Hi,
Thomas Petazzoni wrote,

Quoted 31 lines

Martin,

Quoted 10 lines · Martin Bark

ping fails to compile with uClibc based toolchains with the error

undefined reference to `__finite'

Add a patch to link ping against libm to resolve the math library function finite().

Note, this error is not seen with glibc based toolchains because finite seems to be resolved in both libm and libc.

Quoted 8 lines

Fixes:
http://autobuild.buildroot.net/results/08f7386f75c881bc582b338824f8ccd509b2921e/
http://autobuild.buildroot.net/results/5aeef61fbd399dd78dc72b9e7cce978e6f1f58b4/

A pull request has been sent to fix this issue upstream, see
https://github.com/iputils/iputils/pull/42

Signed-off-by Martin Bark <[email protected]>

Thanks for working on this issue. However, I am not entirely happy with the explanation.

Indeed, if you try to build iputils against uClibc, it builds just fine. It is apparently only when the entire build is done with BR2_ENABLE_DEBUG=y that the build failure occurs. And your commit log doesn't explain at all why the problem only occurs when the build is done with debugging symbols enabled.

Quoted 8 lines

I've tried building iputils against uClibc, it works fine. I've tried building iputils against uClibc with BR2_ENABLE_DEBUG=y (using a pre-built uClibc toolchain, which isn't built with debugging symbols), and it works fine. So it seems that it only happens when the entire build is done with debugging symbols, including uClibc itself.

While linking with -lm might be the correct fix, I am not convinced yet due the lack of explanation for the root of the problem.

The root of the problem is rather simple. When you use math library functions you are required to link libm explicitely. I think for historical reasons. For musl this is no issue as everything is included in libc.so. In uClibc world you have the choice and could simply build a system without any math library.
GNU libc seems to have weak aliases for finitef even in libc.so:
nm output/build/glibc-2.22/build/libc.so|grep finitef 0002ba9c W finitef
0002ba9c T __finitef
0002ba9c t __GI___finitef

So linking with GNU libc does not fail for iputils even without -lm.

Not sure, I cannot find every libm function, but some. tgamma or exp10 is not referenced in libc.so.

May be Mike can explain the Glibc behaviour?

The finite macros where added here:
http://cgit.uclibc-ng.org/cgi/cgit/uclibc-ng.git/commit/include/math.h?id=21902b578e96fd6b85b9bcda8a0e929fc844ec51
So 1.0.10 is the first release containing this BSD specific functions in a usable way.

I think BR2_*DEBUG* option is not related to this error.

best regards
Waldemar

I can't reproduce the issues you see. I just ran some more tests and for me iputils fails with undefined reference to `__finite' when built against uClibc regardless of BR2_ENABLE_DEBUG=y. I had a defconfig with only BR2_PACKAGE_IPUTILS=y.

I looked at the autobuild fails for iputils from here
http://autobuild.buildroot.org/?reason=iputils-c8ff6feaf0442f8efd96ccb415770c54f9e84d47
and there are lots of fails without BR2_ENABLE_DEBUG=y

Quoted 4 lines

The finite macros where added here:
http://cgit.uclibc-ng.org/cgi/cgit/uclibc-ng.git/commit/include/math.h?id=21902b578e96fd6b85b9bcda8a0e929fc844ec51
So 1.0.10 is the first release containing this BSD specific functions in a usable way.

The root of the problem is rather simple. When you use math library functions you are required to link libm explicitely. I think for historical reasons. For musl this is no issue as everything is included in libc.so. In uClibc world you have the choice and could simply build a system without any math library.
GNU libc seems to have weak aliases for finitef even in libc.so:
nm output/build/glibc-2.22/build/libc.so|grep finitef 0002ba9c W finitef
0002ba9c T __finitef
0002ba9c t __GI___finitef

So linking with GNU libc does not fail for iputils even without -lm.

Not sure, I cannot find every libm function, but some. tgamma or exp10 is not referenced in libc.so.

May be Mike can explain the Glibc behaviour?

The finite macros where added here:
http://cgit.uclibc-ng.org/cgi/cgit/uclibc-ng.git/commit/include/math.h?id=21902b578e96fd6b85b9bcda8a0e929fc844ec51
So 1.0.10 is the first release containing this BSD specific functions in a usable way.

I think BR2_*DEBUG* option is not related to this error.

Hello,

Quoted 16 lines · Waldemar Brodkorb

The root of the problem is rather simple. When you use math library functions you are required to link libm explicitely. I think for historical reasons. For musl this is no issue as everything is included in libc.so. In uClibc world you have the choice and could simply build a system without any math library.
GNU libc seems to have weak aliases for finitef even in libc.so:
nm output/build/glibc-2.22/build/libc.so|grep finitef 0002ba9c W finitef
0002ba9c T __finitef
0002ba9c t __GI___finitef

So linking with GNU libc does not fail for iputils even without -lm.

Not sure, I cannot find every libm function, but some. tgamma or exp10 is not referenced in libc.so.

Quoted 8 lines

May be Mike can explain the Glibc behaviour?

The finite macros where added here:
http://cgit.uclibc-ng.org/cgi/cgit/uclibc-ng.git/commit/include/math.h?id=21902b578e96fd6b85b9bcda8a0e929fc844ec51
So 1.0.10 is the first release containing this BSD specific functions in a usable way.

I think BR2_*DEBUG* option is not related to this error.

OK, but how do you explain that:

BR2_arm=y
BR2_TOOLCHAIN_EXTERNAL=y
BR2_TOOLCHAIN_EXTERNAL_CUSTOM=y
BR2_TOOLCHAIN_EXTERNAL_DOWNLOAD=y BR2_TOOLCHAIN_EXTERNAL_URL="http://autobuild.buildroot.org/toolchains/tarballs/br-arm-full-2015.11-rc1-71-g90d1299.tar.bz2" BR2_TOOLCHAIN_EXTERNAL_GCC_4_7=y
BR2_TOOLCHAIN_EXTERNAL_HEADERS_3_10=y
BR2_TOOLCHAIN_EXTERNAL_LOCALE=y
# BR2_TOOLCHAIN_EXTERNAL_HAS_THREADS_DEBUG is not set
BR2_TOOLCHAIN_EXTERNAL_INET_RPC=y
BR2_TOOLCHAIN_EXTERNAL_CXX=y
BR2_INIT_NONE=y
BR2_SYSTEM_BIN_SH_NONE=y
# BR2_PACKAGE_BUSYBOX is not set
BR2_PACKAGE_IPUTILS=y
# BR2_TARGET_ROOTFS_TAR is not set

Builds just fine (and uses uClibc 1.0.9) ?

I think the difference is in gcc versions. It looks like gcc 4.7 in that
external toolchain uses a built-in inline version of __finite(), while gcc 4.9 just calls the external function. I don't think it has anything to do with the uClibc version (though I didn't try all combinations). But for sure, it fails with gcc 4.9 and uClibc 1.0.10 while it succeeds with the same config and gcc 4.7.

I don't think BR2_ENABLE_DEBUG has anything to do with it, but I didn't test that.

Anyway, it seems obvious to me that if you use finite(), then you should link
with -lm. There's bound to be some combination of libc and compiler that requires -lm.

Acked-by Arnout Vandecappelle (Essensium/Mind) <[email protected]>

ping fails to compile with uClibc based toolchains with the error

undefined reference to `__finite'

Add a patch to link ping against libm to resolve the math library function finite().

Note, this error is not seen with glibc based toolchains because finite seems to be resolved in both libm and libc.

Fixes:
http://autobuild.buildroot.net/results/08f7386f75c881bc582b338824f8ccd509b2921e/
http://autobuild.buildroot.net/results/5aeef61fbd399dd78dc72b9e7cce978e6f1f58b4/

A pull request has been sent to fix this issue upstream, see
https://github.com/iputils/iputils/pull/42

Signed-off-by Martin Bark <[email protected]>

---
 package/iputils/0001-ping-link-against-libm.patch | 29 +++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 package/iputils/0001-ping-link-against-libm.patch