Android is not GNU, so don't claim that it is.

[kristina]

Seems good, it could eliminate the need for a lot of preprocessor checks like #if __gnu_linux__ && !defined(__ANDROID__). It doesn't seem that there are any preprocessor checks where this would cause problems (from a quick search) since all of them seem to focus on making sure __gnu_linux__ being defined explicitly excludes Android from those paths.

[srhines]

Sorry about the delay.

lib/Basic/Targets/OSTargets.h

 template <typename Target>
 class LLVM_LIBRARY_VISIBILITY LinuxTargetInfo : public OSTargetInfo<Target> {
 protected:
   void getOSDefines(const LangOptions &Opts, const llvm::Triple &Triple,
                     MacroBuilder &Builder) const override {
     // Linux defines; list based off of gcc output
     DefineStd(Builder, "unix", Opts);
     DefineStd(Builder, "linux", Opts);
-    Builder.defineMacro("__gnu_linux__");
     Builder.defineMacro("__ELF__");
     if (Triple.isAndroid()) {
       Builder.defineMacro("__ANDROID__", "1");
       unsigned Maj, Min, Rev;
       Triple.getEnvironmentVersion(Maj, Min, Rev);
       this->PlatformName = "android";
       this->PlatformMinVersion = VersionTuple(Maj, Min, Rev);
       if (Maj)
         Builder.defineMacro("__ANDROID_API__", Twine(Maj));
+    } else {
+        Builder.defineMacro("__gnu_linux__");
     }
     if (Opts.POSIXThreads)
       Builder.defineMacro("_REENTRANT");
     if (Opts.CPlusPlus)
       Builder.defineMacro("_GNU_SOURCE");
     if (this->HasFloat128)
       Builder.defineMacro("__FLOAT128__");
   }

test/Preprocessor/init.c

 // RUN: %clang_cc1 -x c++ -std=c++98 -fno-rtti -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix NORTTI %s
 // NORTTI: #define __GXX_ABI_VERSION {{.*}}
 // NORTTI-NOT:#define __GXX_RTTI
 // NORTTI:#define __STDC__ 1
 //
 // RUN: %clang_cc1 -triple arm-linux-androideabi -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix ANDROID %s
 // ANDROID-NOT:#define __ANDROID_API__
 // ANDROID:#define __ANDROID__ 1
+// ANDROID-NOT:#define __gnu_linux__
 //
 // RUN: %clang_cc1 -x c++ -triple i686-linux-android -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix I386-ANDROID-CXX %s
 // I386-ANDROID-CXX:#define __STDCPP_DEFAULT_NEW_ALIGNMENT__ 8U
 //
 // RUN: %clang_cc1 -x c++ -triple x86_64-linux-android -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix X86_64-ANDROID-CXX %s
 // X86_64-ANDROID-CXX:#define __STDCPP_DEFAULT_NEW_ALIGNMENT__ 16UL
 //
 // RUN: %clang_cc1 -triple arm-linux-androideabi20 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix ANDROID20 %s
 // ANDROID20:#define __ANDROID_API__ 20
 // ANDROID20:#define __ANDROID__ 1
+// ANDROID-NOT:#define __gnu_linux__
 //
 // RUN: %clang_cc1 -triple lanai-unknown-unknown -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix LANAI %s
 // LANAI: #define __lanai__ 1
 //
 // RUN: %clang_cc1 -E -dM -ffreestanding -triple=amd64-unknown-openbsd6.1 < /dev/null | FileCheck -match-full-lines -check-prefix OPENBSD %s
 // RUN: %clang_cc1 -E -dM -ffreestanding -triple=aarch64-unknown-openbsd6.1 < /dev/null | FileCheck -match-full-lines -check-prefix OPENBSD %s
 // RUN: %clang_cc1 -E -dM -ffreestanding -triple=arm-unknown-openbsd6.1-gnueabi < /dev/null | FileCheck -match-full-lines -check-prefix OPENBSD %s
 // RUN: %clang_cc1 -E -dM -ffreestanding -triple=i386-unknown-openbsd6.1 < /dev/null | FileCheck -match-full-lines -check-prefix OPENBSD %s