[BUG] NDK-r25 CMAKE_BUILD_TYPE=MinSizeRel(-Os) CMAKE_BUILD_TYPE=Release(null), NDK-r22b get MinSizeRel(-Os) Release(-O2)

[DaydreamCoding]

Description

The NDK r25 compile with CMAKE_BUILD_TYPE=Release missing default compiler optimizations options.

R22b

• MinSizeRel -Os -DNDEBUG -fPIE
• Release -O2 -DNDEBUG -fPIE

R25, R24, R23c

• MinSizeRel -Os -DNDEBUG -fPIE
• Release -DNDEBUG -fPIE

Example: project https://github.com/DaydreamCoding/neon-intrinsics-test/tree/1c123bc9391eec4f9c8305d17f9d24e69d70f237

• R22b CMAKE_BUILD_TYPE=Release
  export ANDROID_NDK=$ANDROID_NDK_R22b
  ./build/android_build_Release.sh
  cat build/libsample/build/android/arm64-v8a/test/CMakeFiles/test.dir/flags.make
  CXX_FLAGS = -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security -O2 -DNDEBUG -fPIE

• R22b CMAKE_BUILD_TYPE=MinSizeRel
  export ANDROID_NDK=$ANDROID_NDK_R22b
  ./build/android_build_MinSizeRel.sh
  cat build/libsample/build/android/arm64-v8a/test/CMakeFiles/test.dir/flags.make
  CXX_FLAGS = -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security -Os -DNDEBUG -fPIE

• R25 CMAKE_BUILD_TYPE=Release
  export ANDROID_NDK=$ANDROID_NDK_R25
  ./build/android_build_Release.sh
  cat build/libsample/build/android/arm64-v8a/test/CMakeFiles/test.dir/flags.make
  CXX_FLAGS = -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security -DNDEBUG -fPIE

• R25 CMAKE_BUILD_TYPE=MinSizeRel
  export ANDROID_NDK=$ANDROID_NDK_R25
  ./build/android_build_MinSizeRel.sh
  cat build/libsample/build/android/arm64-v8a/test/CMakeFiles/test.dir/flags.make
  CXX_FLAGS = -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security -Os -DNDEBUG -fPIE

This is very confusing behavior, R22b Release and MinSizeRel both have default compilation optimizations, R25 MinSizeRel does and Release does not

cmake --version
cmake version 3.23.2

CMake suite maintained and supported by Kitware (kitware.com/cmake).

Associated issue
#1693
#1607

Affected versions

r25

Canary version

No response

Host OS

Mac

Host OS version

macOS 12.4

Affected ABIs

arm64-v8a

Build system

CMake

Other build system

No response

minSdkVersion

21

Device API level

No response

[DanAlbert]

Here are some relevant discussions for r23b (probably not useful until you've read the rest of this post though):

#1536
https://android-review.googlesource.com/c/platform/ndk/+/1826817
https://github.com/android/ndk/wiki/Changelog-r23#r23b

The changelog mentions only -Oz, not -O2, which was a gap in the documentation. If I use your build script with r23b, I see -O3 rather than nothing or -O2. That was intentional. Like the bug says, the bandaid was already off, so we took the opportunity to align with CMake's upstream behavior. CMake uses -O3 for Release, -Os for MinSizeRel, and -O2 for RelWithDebInfo.

This has actually been broken since r23b, but was asymptomatic in the default configuration because it's only present in the legacy toolchain file, and even then only in a CMake configuration that AGP does not use. If I force r23b to use the legacy toolchain, I get the same behavior there. It seems that Release (and only Release) is missing optimization flags. MinSizeRel and RelWithDebInfo are getting -Os and -O2 respectively as expected.

I'll upload a fix shortly, since as best as I can make out this was not intentional. It's not strictly a regression either (the same configuration behaves the same way), but since the default behavior has changed to include this bug, I think this is worth getting into r25b (no current release plans for that, but I'll start kicking those tires since we also have some toolchain fixes we want to ship).

[DanAlbert]

https://android-review.googlesource.com/c/platform/ndk/+/2168845

Thanks for the detailed bug report and repro instructions btw. It still took a lot of head scratching to figure out what broke and when, but it would have been a lot harder without that :)

[DanAlbert]

https://ci.android.com/builds/branches/aosp-master-ndk/grid?head=8881098&tail=8881098 has the fix if you want to double check. I added tests to cover the missing configurations, but I haven't retested your repro case against the fixed NDK.

[DaydreamCoding]

Thanks for your reply and fix. with r25b we can distribute this version on a large scale without having to change a lot of source code build parameters. this will be the most reliable version since the r22b.