NDK + gradle: Which NDK API level is used?

Chris Browet

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Mar 28, 2019, 11:22:06 AM3/28/19

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Hi,

I'm adjusting my builds to NDK 19 and the deprecation of the toolchains, and I come to realize that I have no clue which NDK API gradle is using to build app.

Even building in verbose doesn't make it clear.

A warning sign came when I saw

debugUnsigned|arm64-v8a :-- Check for working C compiler: /opt/android-dev/android-ndk-r19c/toolchains/llvm/prebuilt/linux-x86_64/bin/clang -- works

in my logs, where I would be expecting something like "/opt/android-dev/android-ndk-r19c/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android21-clang".

It is quite important (I think) when it come to linking the proper versions of libandroid and libmediandk.

Is it somehow automagically deduced from minSdkVersion of build.gradle, or... ?

What is "/opt/android-dev/android-ndk-r19c/toolchains/llvm/prebuilt/linux-x86_64/bin/clang" vs., e.g., "/opt/android-dev/android-ndk-r19c/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android21-clang"?

Thanks

Dan Albert

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Mar 28, 2019, 12:25:34 PM3/28/19

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Yes, NDK API level is minSdkVersion (or the lowest available API level for the architecture, if minSdkVersion is below it; 21 is the oldest API level that supports arm64). The 21 in the compiler triple is the API level.

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Chris Browet

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Mar 28, 2019, 1:39:36 PM3/28/19

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Thanks Dan.

Can you also enlight me re "/opt/android-dev/android-ndk-

r19c/toolchains/llvm/prebuilt/linux-x86_64/bin/clang" vs., e.g., "/opt/android-dev/android-ndk-r19c/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android21-clang"?

What is the "generic" clang? A wrapper of sorts?

On Thursday, 28 March 2019 17:25:34 UTC+1, Dan Albert wrote:

Yes, NDK API level is minSdkVersion (or the lowest available API level for the architecture, if minSdkVersion is below it; 21 is the oldest API level that supports arm64). The 21 in the compiler triple is the API level.

On Thu, Mar 28, 2019, 08:22 Chris Browet <christi...@gmail.com> wrote:

Hi,

I'm adjusting my builds to NDK 19 and the deprecation of the toolchains, and I come to realize that I have no clue which NDK API gradle is using to build app.
Even building in verbose doesn't make it clear.

A warning sign came when I saw
debugUnsigned|arm64-v8a :-- Check for working C compiler: /opt/android-dev/android-ndk-r19c/toolchains/llvm/prebuilt/linux-x86_64/bin/clang -- works
in my logs, where I would be expecting something like "/opt/android-dev/android-ndk-r19c/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android21-clang".

It is quite important (I think) when it come to linking the proper versions of libandroid and libmediandk.

Is it somehow automagically deduced from minSdkVersion of build.gradle, or... ?
What is "/opt/android-dev/android-ndk-r19c/toolchains/llvm/prebuilt/linux-x86_64/bin/clang" vs., e.g., "/opt/android-dev/android-ndk-r19c/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android21-clang"?

Thanks
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Dan Albert

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Mar 28, 2019, 1:42:31 PM3/28/19

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The non-prefixed Clang is the actual Clang. Clang is a cross-compiler by default. The prefixed Clangs are the wrappers (if you inspect them, you'll see that they're shell/batch scripts that invoke the real Clang) that select the correct target triple to aid tools like autoconf that aren't set up to pass --target explicitly.

See https://android.googlesource.com/platform/ndk/+/master/docs/BuildSystemMaintainers.md#Clang for more info.

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Chris Browet

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Mar 28, 2019, 2:51:49 PM3/28/19

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Great. Thanks for the clarifications.

On Thursday, 28 March 2019 18:42:31 UTC+1, Dan Albert wrote:

The non-prefixed Clang is the actual Clang. Clang is a cross-compiler by default. The prefixed Clangs are the wrappers (if you inspect them, you'll see that they're shell/batch scripts that invoke the real Clang) that select the correct target triple to aid tools like autoconf that aren't set up to pass --target explicitly.

See https://android.googlesource.com/platform/ndk/+/master/docs/BuildSystemMaintainers.md#Clang for more info.

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