undefined reference to 'log2f' on android

[not-fl3]

I tried this code:

fn main() {
    let _ = 10.0f32.log2();
}

Everithing was fine without cross compilation, but with

rustc aaa.rs --target=arm-linux-androideabi -C linker="arm-linux-androideabi-gcc-4.8"

i got followed result:

error: linking with arm-linux-androideabi-gcc-4.8 failed: exit code: 1
note: "arm-linux-androideabi-gcc-4.8" "-Wl,--as-needed" "-Wl,--allow-multiple-definition" "-L" "/usr/local/lib64/rustlib/arm-linux-androideabi/lib" "aaa.0.o" "-o" "aaa" "-Wl,--gc-sections" "-pie" "-nodefaultlibs" "-L" "/usr/local/lib64/rustlib/arm-linux-androideabi/lib" "-Wl,-Bstatic" "-Wl,-Bdynamic" "/usr/local/lib64/rustlib/arm-linux-androideabi/lib/libstd-db5a760f.rlib" "/usr/local/lib64/rustlib/arm-linux-androideabi/lib/libcollections-db5a760f.rlib" "/usr/local/lib64/rustlib/arm-linux-androideabi/lib/librustc_unicode-db5a760f.rlib" "/usr/local/lib64/rustlib/arm-linux-androideabi/lib/librand-db5a760f.rlib" "/usr/local/lib64/rustlib/arm-linux-androideabi/lib/liballoc-db5a760f.rlib" "/usr/local/lib64/rustlib/arm-linux-androideabi/lib/liballoc_jemalloc-db5a760f.rlib" "/usr/local/lib64/rustlib/arm-linux-androideabi/lib/liblibc-db5a760f.rlib" "/usr/local/lib64/rustlib/arm-linux-androideabi/lib/libcore-db5a760f.rlib" "-l" "dl" "-l" "log" "-l" "gcc" "-l" "gcc" "-l" "c" "-l" "m" "-pie" "-l" "compiler-rt"
note: aaa.0.o:aaa.0.rs:function f32::f32::log2::h94a06ad56bda381bXwa: error: undefined reference to 'log2f'
collect2: error: ld returned 1 exit status

error: aborting due to previous error

While with log(), not log2() everithing works fine.

Meta

rustc --version --verbose:

rustc 1.8.0-dev (cd1b845 2016-01-22)
binary: rustc
commit-hash: cd1b845
commit-date: 2016-01-22
host: x86_64-unknown-linux-gnu
release: 1.8.0-dev

[alexcrichton]

Hm unfortunately I can't seem to reproduce this. To help diagnose:

• Where'd you install rustc from?
• Where'd you install the arm-linux-androideabi Rust standard library from?
• Where'd you install the NDK from? (the command line to install it would also be useful here)

For reference I ran this inside of the rust-buildbot android docker image (which has the ndk version r10e), I installed rustc through multirust and the Rust standard library via a custom download of the nightlies we're producing.

[not-fl3]

Answering your questions i maybe have found problem: i made NDK with
make-standalone-toolchain.sh
--platform=android-14
--arch=arm
--install-dir=~/ndk-standalone-14-arm

with android-18 everithing linking fine.
So, for me, its reproducable on any api level below 18.

[alexcrichton]

Ok, thanks for the info! That'd definitely explain the linker error here.

Currently our nightlies are compiled with the API level 18 (I believe), which would explain why we haven't seen this. I don't believe that we have any particular reason for choosing (that I know of at least), but I'm curious if you're trying to specifically target 14? If that's a big enough use case we could consider moving our nightlies back to an older API level.

[not-fl3]

For me its not an issue at this moment, i just didn know about such restriction :)

[alexcrichton]

Ah ok, in that case I'm going to close as our minimum API version level is 18 currently, but if this becomes an issue please let us know! It may not be too hard to go backwards even farther.

[kanerogers]

Hi, there!

I've been having this same issue, and after a fair bit of Googling, I've finally stumbled upon this issue.

A bit of a shame that the minimum API is 18 - the target I'm compiling for is 16, which along with 17 comprises 20.5% of the Android market at time of writing.

If it's not too much work to backport, API level 16 is the minimum API version used in a number of other projects (eg. React Native).

Please let me know if there's anything further I can do to assist.

[alexcrichton]

Yeah I'm pretty sure we'd be fine going backwards to a previous API revision so long as we don't lose any major functionality. The steps to do so would be:

1. Updated the android buildslave to have an API-level 16 NDK and emulator image
2. Update the buildmaster config to use the older NDK.
3. Update the standard library to run all tests with the API level 16 NDK

Once that's all done we can take care of updating the actual prod buildbots to the newer images.

[kanerogers]

Thanks for your help, Alex!

Would you like me to go ahead and do this in a branch and return back?

K
On Mon, 7 Mar 2016 at 5:37 AM, Alex Crichton notifications@github.com
wrote:

Yeah I'm pretty sure we'd be fine going backwards to a previous API
revision so long as we don't lose any major functionality. The steps to do
so would be:

1. Updated the android buildslave
   https://github.com/rust-lang/rust-buildbot/tree/master/slaves/android
   to have an API-level 16 NDK and emulator image
2. Update the buildmaster config
   https://github.com/rust-lang/rust-buildbot/blob/master/master/master.cfg
   to use the older NDK.
3. Update the standard library to run all tests with the API level 16
   NDK

Once that's all done we can take care of updating the actual prod
buildbots to the newer images.

—
Reply to this email directly or view it on GitHub
#31119 (comment).

[alexcrichton]

Sure! If we get to the point where we're dropping a lot of support in the standard library to go back in API revisions we may need to rethink, but it likely won't come to that.

[kanerogers]

Thanks, @alexcrichton. 😄

I've created a PR for rust-buildbot here, but I'm a little unsure how I can

Update the standard library to run all tests with the API level 16 NDK

If you're able to please point me in the right direction, I'll get it done!