- The way CMake (our build system) does Android support is we feed it an android.toolchain.cmake from NDK_HOME and this sets all relevant variables. It doesn't appear to set __ANDROID_API__, nor does our CMakeLists.txt (CMake project config).
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I cannot vouch for our current system as I did not design it. I maintained the prior build system, which had Gradle invoking CMake. The pure-CMake setup is new. It's possible Gradle read AndroidManifest.xml, saw the minSdkVersion there, and translated that into a CMake define...
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If this is the case, then this simply means that our new non-Gradle setup would need to have the human specify those AndroidManifest.xml-related defines by hand. But I'm not clear who they should be defined to (to CMake? To toolchain.cmake? To clang?)
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It does seem real suspicious that -DFORTIFY_SOURCE=2 is being set but ONLY on the .c files that are building wrong, and I have literally no idea where that -D came from because we didn't tell it to do that.
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You definitely need -D__ANDROID_API__=21 in CPPFLAGS to match your minSdkVersion 21. It's broken overall, but you only happen to be seeing it when _FORTIFY_SOURCE is used because _FORTIFY_SOURCE will automatically use the new symbols introduced for newly fortified functions.
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If you run `CPPFLAGS=-D__ANDROID_API__=21 cmake` instead of `cmake`, that may work properly.
I don't understand why it would ever be not enabling _FORTIFY_SOURCE=2 by default unless it's building those files without optimization. It's generally passed by default everywhere.
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As an interesting fact, I am (as noted I am getting used to a new version of the build process) not sure if I am building debug or release. Possibly I am building both at once, or neither.
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It *sounds* like it might be optimizing some files (where it would pass -D_FORTIFY_SOURCE=2 by default) and not others. The _FORTIFY_SOURCE thing is just what let you know it's broken though. Real issue is not having minSdkVersion set for C and C++ so it's defaulting to 30+.
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Okay so check this out, if I manually set the __ANDROID_API__ it says I defined it twice. Could --target=aarch64-none-linux-android26 be doing something magic?
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You probably just need to set --target=aarch64-none-linux-android21 rather than --target=aarch64-none-linux-android26. It's the minSdkVersion that needs to be set at compile time for __ANDROID_API__ rather than the targetSdkVersion which is checked at runtime.
Since your code needs to link properly in an Android API 21 environment since minSdkVersion is 21. Stuff that varies based on targetSdkVersion has to be handled at runtime.
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So, I believe what is controlling this is -D ANDROID_NATIVE_API_LEVEL=26 , which is being passed to CMake (not clang) and is most likely being interpreted by the CMake toolchain file (script). Problem: If I set this to 21, I get this legitimate-looking error:
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