Android: Switch to native ELF TLS & latest LTS NDK

.github/actions/3-build-cross/action.yml

@@ -14,10 +14,10 @@ inputs:
     default: false
   android_ndk_version:
     required: false
-    default: r21e
+    default: r26c
   android_api_level:
     required: false
-    default: 21
+    default: 29
 runs:
   using: composite
   steps:
@@ -92,30 +92,28 @@ runs:
         cd ..
         version='${{ inputs.android_ndk_version }}'
         curl -fL --retry 3 --max-time 300 -o android-ndk.zip \
-          https://dl.google.com/android/repository/android-ndk-$version-linux-x86_64.zip
+          https://dl.google.com/android/repository/android-ndk-$version-linux.zip
         unzip android-ndk.zip >/dev/null
         mv "android-ndk-$version" android-ndk
         rm android-ndk.zip
 
-        # The NDK toolchain file enforces `-g` as base C[XX] flag - remove it to
-        # *significantly* reduce executable sizes
-        toolchainFile="$PWD/android-ndk/build/cmake/android.toolchain.cmake"
-        sed -i 's|^  -g$||' "$toolchainFile"
-
         arch='${{ inputs.arch }}'
         apiLevel='${{ inputs.android_api_level }}'
         cmakeFlags="-DTARGET_SYSTEM='Android;Linux;UNIX'"
         if [[ "$arch" == armv7a ]]; then
           triple="$arch-linux-androideabi$apiLevel"
           cmakeFlags+=' -DANDROID_ABI=armeabi-v7a'
         elif [[ "$arch" == aarch64 ]]; then
+          # FIXME: as of NDK rc26c, libc.a has __tls_get_addr, but libc.so only since API level 30 (Android v11)
+          apiLevel=30
           triple="$arch-linux-android$apiLevel"
           cmakeFlags+=' -DANDROID_ABI=arm64-v8a'
         fi
         cmakeFlags+=" -DANDROID_NATIVE_API_LEVEL=$apiLevel"
         cmakeFlags+=" -DANDROID_STL=c++_static"
-        cmakeFlags+=" -DCMAKE_TOOLCHAIN_FILE=$toolchainFile"
-        cmakeFlags+=" -DLDC_LINK_MANUALLY=ON -DD_LINKER_ARGS='-fuse-ld=bfd;-L$PWD/build-cross-libs/lib;-lphobos2-ldc;-ldruntime-ldc'"
+        cmakeFlags+=" -DCMAKE_TOOLCHAIN_FILE=$PWD/android-ndk/build/cmake/android.toolchain.cmake"
+        cmakeFlags+=" -DANDROID_USE_LEGACY_TOOLCHAIN_FILE=OFF"
+        cmakeFlags+=" -DLDC_LINK_MANUALLY=ON -DD_LINKER_ARGS='-L$PWD/build-cross-libs/lib;-lphobos2-ldc;-ldruntime-ldc'"
 
         echo "DFLAGS=-mtriple=$triple -fvisibility=hidden -L-L$PWD/build-cross-libs/lib -gcc=$PWD/android-ndk/toolchains/llvm/prebuilt/linux-x86_64/bin/$triple-clang" >> $GITHUB_ENV
         echo "CROSS_TRIPLE=$triple" >> $GITHUB_ENV

driver/linker-gcc.cpp

@@ -621,14 +621,6 @@ void ArgsBuilder::build(llvm::StringRef outputPath,
 void ArgsBuilder::addLinker() {
   llvm::StringRef linker = opts::linker;
 
-  // Default to ld.bfd for Android (placing .tdata and .tbss sections adjacent
-  // to each other as required by druntime's rt.sections_android, contrary to
-  // gold and lld as of Android NDK r21d).
-  if (global.params.targetTriple->getEnvironment() == llvm::Triple::Android &&
-      opts::linker.getNumOccurrences() == 0) {
-    linker = "bfd";
-  }
-
   if (!linker.empty())
     args.push_back(("-fuse-ld=" + linker).str());
 }

driver/main.d

@@ -59,18 +59,3 @@ version (Windows)
         SetConsoleOutputCP(originalOutputCP);
     }
 }
-
-// TLS bracketing symbols required for our custom TLS emulation on Android
-// as we don't have a D main() function for LDC and LDMD.
-version (Android)
-{
-    import ldc.attributes;
-
-    extern(C) __gshared
-    {
-        @section(".tdata")
-        int _tlsstart = 0;
-        @section(".tcommon")
-        int _tlsend = 0;
-    }
-}

driver/targetmachine.cpp

@@ -639,12 +639,14 @@ createTargetMachine(const std::string targetTriple, const std::string arch,
     targetOptions.DataSections = true;
   }
 
-  // On Android, we depend on a custom TLS emulation scheme implemented in our
-  // LLVM fork. LLVM 7+ enables regular emutls by default; prevent that.
+  // On Android, enforce native ELF TLS (supported since API level 29 = Android
+  // v10), as required by druntime. (Some older LLVM versions might default to
+  // EmuTLS).
   if (triple.getEnvironment() == llvm::Triple::Android) {
     targetOptions.EmulatedTLS = false;
 #if LDC_LLVM_VER < 1700
-    // Removed in this commit: https://github.com/llvm/llvm-project/commit/0d333bf0e3aa37e2e6ae211e3aa80631c3e01b85
+    // Removed in this commit:
+    // https://github.com/llvm/llvm-project/commit/0d333bf0e3aa37e2e6ae211e3aa80631c3e01b85
     targetOptions.ExplicitEmulatedTLS = true;
 #endif
   }

runtime/druntime/src/rt/sections.d

@@ -64,7 +64,7 @@ else version (CRuntime_Microsoft)
         public import rt.sections_win64;
 }
 else version (CRuntime_Bionic)
-    public import rt.sections_android;
+    public import rt.sections_elf_shared;
 else version (CRuntime_UClibc)
     public import rt.sections_elf_shared;
 else

runtime/druntime/src/rt/sections_android.d

@@ -10,6 +10,8 @@
 
 module rt.sections_android;
 
+version (LDC) { /* implemented in rt.sections_elf_shared */ } else:
+
 version (CRuntime_Bionic):
 
 // debug = PRINTF;

runtime/druntime/src/rt/sections_elf_shared.d

@@ -24,6 +24,7 @@ else version (CRuntime_Musl) enum SharedELF = true;
 else version (FreeBSD) enum SharedELF = true;
 else version (NetBSD) enum SharedELF = true;
 else version (DragonFlyBSD) enum SharedELF = true;
+else version (CRuntime_Bionic) enum SharedELF = true;
 else version (CRuntime_UClibc) enum SharedELF = true;
 else enum SharedELF = false;