lldb: Don't check for CMAKE_SYSTEM_NAME==Android.

[pcc]

Summary

CMAKE_SYSTEM_NAME seems to be unreliable for detecting whether the
target is Android. At least on my machine it always turns out to
have the value Linux when targeting Android. Even explicitly passing
-DCMAKE_SYSTEM_NAME=Android to CMake doesn't seem to help. It seems
that CMake is overriding the value that I pass in with a value that
it computed somehow.

To avoid relying on whichever fragile mechanism is used to detect
Android targets, let's just compile the Android source files
unconditionally and use the preprocessor to exclude their contents
on non-Android platforms.

[labath]

How exactly are you building this? CMAKE_SYSTEM_NAME is set in the official android cmake toolchain file (https://android.googlesource.com/platform/ndk/+/refs/heads/ndk-release-r23/build/cmake/android.toolchain.cmake#213)

[pcc]

In D103127#2985203, @labath wrote:

How exactly are you building this? CMAKE_SYSTEM_NAME is set in the official android cmake toolchain file (https://android.googlesource.com/platform/ndk/+/refs/heads/ndk-release-r23/build/cmake/android.toolchain.cmake#213)

I configured cmake using a script that looks like this:

#!/bin/sh

target_flags='--target=aarch64-linux-android21 --sysroot=/path/to/android-ndk-r21-beta1/toolchains/llvm/prebuilt/linux-x86_64/sysroot --gcc-toolchain=/path/to/android-ndk-r21-beta1/toolchains/llvm/prebuilt/linux-x86_64 -mno-outline-atomics'

cmake \
  -GNinja \
  -DCMAKE_BUILD_TYPE=Release \
  -DLLVM_ENABLE_ASSERTIONS=ON \
  -DCMAKE_C_COMPILER=`pwd`/../ra/bin/clang \
  -DCMAKE_CXX_COMPILER=`pwd`/../ra/bin/clang++ \
  -DLLVM_ENABLE_THREADS=OFF \
  -DLLVM_CONFIG_PATH=`pwd`/../ra/bin/llvm-config \
  "-DCMAKE_C_FLAGS=$target_flags" \
  "-DCMAKE_CXX_FLAGS=$target_flags" \
  "-DCMAKE_ASM_FLAGS=$target_flags" \
  -DSANITIZER_CXX_ABI=none \
  -DSANITIZER_CXX_ABI_LIBRARY=c++abi \
  -DCMAKE_EXE_LINKER_FLAGS="-fuse-ld=lld -Wl,-lstdc++ -static-libstdc++ --rtlib=libgcc" \
  -DCMAKE_SHARED_LINKER_FLAGS=-Wl,-u__cxa_demangle \
  -DANDROID=1 \
  -DCOMPILER_RT_INCLUDE_TESTS=ON \
  "-DCOMPILER_RT_TEST_COMPILER_CFLAGS=$target_flags" \
  -DLLVM_TABLEGEN=`pwd`/../ra/bin/llvm-tblgen \
  -DLLDB_TABLEGEN=`pwd`/../ra/bin/lldb-tblgen \
  -DCLANG_TABLEGEN=`pwd`/../ra/bin/clang-tblgen \
  -DLLVM_ENABLE_PROJECTS='clang;lldb' \
  -DLLDB_ENABLE_LIBEDIT=0 \
  -DLLDB_ENABLE_LIBXML2=0 \
  -DLLVM_HOST_TRIPLE=aarch64-linux-android21 \
  -DCMAKE_SYSTEM_NAME=Android \
  -DLLVM_TARGETS_TO_BUILD='X86;AArch64' \
  ../../llvm

But now I'm switching to gn to build LLDB, so I don't need to worry about this any more.

[labath]

In D103127#2990249, @pcc wrote:

In D103127#2985203, @labath wrote:

How exactly are you building this? CMAKE_SYSTEM_NAME is set in the official android cmake toolchain file (https://android.googlesource.com/platform/ndk/+/refs/heads/ndk-release-r23/build/cmake/android.toolchain.cmake#213)

I configured cmake using a script that looks like this:

#!/bin/sh

target_flags='--target=aarch64-linux-android21 --sysroot=/path/to/android-ndk-r21-beta1/toolchains/llvm/prebuilt/linux-x86_64/sysroot --gcc-toolchain=/path/to/android-ndk-r21-beta1/toolchains/llvm/prebuilt/linux-x86_64 -mno-outline-atomics'

cmake \
  -GNinja \
  -DCMAKE_BUILD_TYPE=Release \
  -DLLVM_ENABLE_ASSERTIONS=ON \
  -DCMAKE_C_COMPILER=`pwd`/../ra/bin/clang \
  -DCMAKE_CXX_COMPILER=`pwd`/../ra/bin/clang++ \
  -DLLVM_ENABLE_THREADS=OFF \
  -DLLVM_CONFIG_PATH=`pwd`/../ra/bin/llvm-config \
  "-DCMAKE_C_FLAGS=$target_flags" \
  "-DCMAKE_CXX_FLAGS=$target_flags" \
  "-DCMAKE_ASM_FLAGS=$target_flags" \
  -DSANITIZER_CXX_ABI=none \
  -DSANITIZER_CXX_ABI_LIBRARY=c++abi \
  -DCMAKE_EXE_LINKER_FLAGS="-fuse-ld=lld -Wl,-lstdc++ -static-libstdc++ --rtlib=libgcc" \
  -DCMAKE_SHARED_LINKER_FLAGS=-Wl,-u__cxa_demangle \
  -DANDROID=1 \
  -DCOMPILER_RT_INCLUDE_TESTS=ON \
  "-DCOMPILER_RT_TEST_COMPILER_CFLAGS=$target_flags" \
  -DLLVM_TABLEGEN=`pwd`/../ra/bin/llvm-tblgen \
  -DLLDB_TABLEGEN=`pwd`/../ra/bin/lldb-tblgen \
  -DCLANG_TABLEGEN=`pwd`/../ra/bin/clang-tblgen \
  -DLLVM_ENABLE_PROJECTS='clang;lldb' \
  -DLLDB_ENABLE_LIBEDIT=0 \
  -DLLDB_ENABLE_LIBXML2=0 \
  -DLLVM_HOST_TRIPLE=aarch64-linux-android21 \
  -DCMAKE_SYSTEM_NAME=Android \
  -DLLVM_TARGETS_TO_BUILD='X86;AArch64' \
  ../../llvm

But now I'm switching to gn to build LLDB, so I don't need to worry about this any more.

Yeah, that's not really the right way to use cmake. You're supposed to create a toolchain file (similar to the android one), and use appropriate cmake variables (like CMAKE_SYSROOT) instead of putting everything inside CXXFLAGS. From within the toolchain file, you could also set the right value of CMAKE_SYSTEM_NAME, and then everything would work.

lldb/source/Host/CMakeLists.txt

else()
   elseif (CMAKE_SYSTEM_NAME MATCHES "Linux|Android")
     add_host_subdirectory(linux
       linux/AbstractSocket.cpp
       linux/Host.cpp
       linux/HostInfoLinux.cpp
       linux/LibcGlue.cpp
       linux/Support.cpp
       )
-    if (CMAKE_SYSTEM_NAME MATCHES "Android")
-      add_host_subdirectory(android
-        android/HostInfoAndroid.cpp
-        android/LibcGlue.cpp
-        )
-    endif()
   elseif (CMAKE_SYSTEM_NAME MATCHES "FreeBSD")
     add_host_subdirectory(freebsd
       freebsd/Host.cpp
       freebsd/HostInfoFreeBSD.cpp
       )
 
   elseif (CMAKE_SYSTEM_NAME MATCHES "NetBSD")
     add_host_subdirectory(netbsd

lldb/source/Host/android/HostInfoAndroid.cpp

 //===-- HostInfoAndroid.cpp -----------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
+#if defined(__ANDROID__)
+
 #include "lldb/Host/android/HostInfoAndroid.h"
 #include "lldb/Host/FileSystem.h"
 #include "lldb/Host/linux/HostInfoLinux.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 
 using namespace lldb_private;
 using namespace llvm;
bool HostInfoAndroid::ComputeTempFileBaseDirectory(FileSpec &file_spec) {
   // algorithm will deduce /tmp, which is plain wrong. In that case we have an
   // invalid directory, we substitute the path with /data/local/tmp, which is
   // correct at least in some cases (i.e., when running as shell user).
   if (!success || !FileSystem::Instance().Exists(file_spec))
     file_spec = FileSpec("/data/local/tmp");
 
   return FileSystem::Instance().Exists(file_spec);
 }
+
+#endif // __ANDROID__

lldb/source/Host/android/LibcGlue.cpp

 //===-- LibcGlue.cpp ------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // This files adds functions missing from libc on earlier versions of Android
 
+#if defined(__ANDROID__)
+
 #include <android/api-level.h>
 
 #include <sys/syscall.h>
 
 #if __ANDROID_API__ < 21
 
 #include <fcntl.h>
 #include <signal.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 
 #include "lldb/Host/Time.h"
 
 time_t timegm(struct tm *t) { return (time_t)timegm64(t); }
 
 int posix_openpt(int flags) { return open("/dev/ptmx", flags); }
 
 #endif
+
+#endif // __ANDROID__