libx265: Disable assembly when building for Android

[uilianries]

Summary

Changes to recipe: libx265/3.4

Motivation

As reported by the issue #23721 the libx265 fails to be built to Android when using the option value assembly=True. This is not only breaking this package, but also affecting ffmpeg directly when cross-building to Android.

It's a known issue reported in the upstream already, but no official solution so far: https://bitbucket.org/multicoreware/x265_git/issues/603/aarch64-assembly-code-failing-when-cross

Details

To build assembly code in x265, it's used a custom command in the project, which propagates manually which flags should be used by the compiler, resulting in failure when cross-build to Android-armv8.

Other package managers tried custom patches (including Gentoo) to solve the case, but it still fails for me locally. For instance, when passing target to build assembly code:

toolchains/llvm/prebuilt/linux-x86_64/bin/clang++ -fPIC --target=aarch64-none-linux-android32  -c /home/uilian/.conan2/p/b/libx2c4053feaf82aa/b/src/source/common/aarch64/mc-a.S -o mc-a.S.o
<instantiation>:11:9: error: unknown directive
        .func x265_pixel_avg_pp_4x4_neon
        ^
<instantiation>:1:1: note: while in macro instantiation
function x265_pixel_avg_pp_4x4_neon
^
/home/uilian/.conan2/p/b/libx2c4053feaf82aa/b/src/source/common/aarch64/mc-a.S:44:1: note: while in macro instantiation
pixel_avg_pp_4xN_neon 4
^
<instantiation>:2:9: error: unknown directive
        .endfunc
        ^

I'll be disabling assembly for now, but keeping it open for contributions, as didn't remove the option.

Full build log for Android with this new change: https://gist.github.com/uilianries/971fc896b481170ee311ac6e9eb35152

closes #23721

Related to #24566

---

• Read the contributing guidelines
• Checked that this PR is not a duplicate: list of PRs by recipe
• Tested locally with at least one configuration using a recent version of Conan

[AbrilRBS]

Minor question regarding how the recipe is handling things, otherwise looks good

[AbrilRBS]

Is this even working? I've submitted conan-io/conan#16672 to show that changing values in config_options will have no effect if the user is setting the option in the CLI

[uilianries]

If you change the option value in config_option, it will change the default value only. In case the user pass assembly=True, the validate_build will take care and raise and error. Indeed the user has priority over the value configured via config_options.

[uilianries]

Also, the build log shows my command line, I didn't enforce the assembly option to False, but it passes:

https://gist.github.com/uilianries/971fc896b481170ee311ac6e9eb35152

In case passing assembly=True it will fail for sure, the issue #23721 has a very similar build log with my current error.

[jcar87]

This is how it has always worked since Conan 1.x - setting the value of an option in config_options makes it the "default" value - and the default value is only used if the user did not override it elsewhere (e.g via CLI).

[AbrilRBS]

Thanks!

[uilianries]

Building for Mac M1 it fails too when the option lix265:assembly=True. It's false by default when using Mac M1, but users can override it via profile.

I added a restriction in validate() to avoid any possible error when trying to build it, so users will be aware about.

Kudos @AbrilRBS for spotting it.

[conan-center-bot]

Conan v1 pipeline ✔️

All green in build 4 (f3187d5b2d351ef5ccb94f86707287d33c54569f):

• libx265/3.4:
  All packages built successfully! (All logs)

• libx265/3.2.1:
  All packages built successfully! (All logs)

---

Conan v2 pipeline ✔️

Note: Conan v2 builds are now mandatory. Please read our discussion about it.

All green in build 4 (f3187d5b2d351ef5ccb94f86707287d33c54569f):

• libx265/3.4:
  All packages built successfully! (All logs)

• libx265/3.2.1:
  All packages built successfully! (All logs)