<div dir="ltr">Hi there,<div><br></div><div>Apologies in advance if this is not the correct mailing list.</div><div><br></div><div>I'm working on a C++ project which has existing CMake files and works on Linux and Mac. I was attempting to build it on the Android NDK cross-compiling to ARM64, and ran into an issue.</div><div><br></div><div>In particular, the toolchain determination for test compilation fails as follows:</div><div><br></div><div><div>    $HOME/Android/Sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin/clang --target=aarch64-none-linux-android --gcc-toolchain=$HOME/Android/Sdk/ndk-bundle/toolchains//prebuilt/linux-x86_64 --sysroot=$HOME/Android/Sdk/ndk-bundle/platforms/android-28/arch-arm64 -funwind-tables -no-canonical-prefixes -D__ANDROID_API__=28 -fexceptions  -g  -fPIE -pie -Wl,--gc-sections  CMakeFiles/cmTC_34db0.dir/testCCompiler.c.o  -o cmTC_34db0 </div><div>    /usr/bin/ld: unrecognised emulation mode: aarch64linux</div></div><div><br></div><div>The problem seems to be where --gcc-toolchain is set to:</div><div><br></div><div><font face="monospace, monospace">$HOME/Android/Sdk/ndk-bundle/toolchains//prebuilt/linux-x86_64</font></div><div><font face="monospace, monospace"><br></font></div><div><font face="arial, helvetica, sans-serif">(note the double slash).</font></div><div><br></div><div>On my installation of the NDK (r19c, Linux), the toolchain seems to be in:</div><div><br></div><div><font face="monospace, monospace">$HOME/Android/Sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/</font></div><div><br></div><div><div>My android.toolchain.cmake file is as follows:<br></div><div><br></div><div><p class="gmail-m_8731808813187148269gmail-p1" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(51,187,200)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures">set</span><span class="gmail-m_8731808813187148269gmail-s2" style="font-variant-ligatures:no-common-ligatures;color:rgb(0,0,0)">(</span><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures">CMAKE_SYSTEM_NAME</span><span class="gmail-m_8731808813187148269gmail-s2" style="font-variant-ligatures:no-common-ligatures;color:rgb(0,0,0)"> Android)</span></p><p class="gmail-m_8731808813187148269gmail-p2" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(0,0,0)"><span class="gmail-m_8731808813187148269gmail-s3" style="font-variant-ligatures:no-common-ligatures;color:rgb(51,187,200)">set</span><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures">(</span><span class="gmail-m_8731808813187148269gmail-s3" style="font-variant-ligatures:no-common-ligatures;color:rgb(51,187,200)">CMAKE_ANDROID_NDK</span><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures"> </span><span class="gmail-m_8731808813187148269gmail-s4" style="font-variant-ligatures:no-common-ligatures;color:rgb(213,59,211)">$ENV{HOME}</span><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures">/Android/Sdk/ndk-bundle)</span></p><p class="gmail-m_8731808813187148269gmail-p1" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(51,187,200)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures">set</span><span class="gmail-m_8731808813187148269gmail-s2" style="font-variant-ligatures:no-common-ligatures;color:rgb(0,0,0)">(</span><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures">CMAKE_ANDROID_NDK_TOOLCHAIN_VERSION</span><span class="gmail-m_8731808813187148269gmail-s2" style="font-variant-ligatures:no-common-ligatures;color:rgb(0,0,0)"> clang)</span></p><p class="gmail-m_8731808813187148269gmail-p1" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(51,187,200)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures">set</span><span class="gmail-m_8731808813187148269gmail-s2" style="font-variant-ligatures:no-common-ligatures;color:rgb(0,0,0)">(</span><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures">CMAKE_ANDROID_ARCH_ABI</span><span class="gmail-m_8731808813187148269gmail-s2" style="font-variant-ligatures:no-common-ligatures;color:rgb(0,0,0)"> arm64-v8a)</span></p><p class="gmail-m_8731808813187148269gmail-p1" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(51,187,200)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures">set</span><span class="gmail-m_8731808813187148269gmail-s2" style="font-variant-ligatures:no-common-ligatures;color:rgb(0,0,0)">(</span><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures">CMAKE_ANDROID_STL_TYPE</span><span class="gmail-m_8731808813187148269gmail-s2" style="font-variant-ligatures:no-common-ligatures;color:rgb(0,0,0)"> c++_shared)</span></p></div><div><br></div><div></div></div><div>I was able to get it to work by applying the small patch below:</div><div><br></div><div><p class="gmail-m_8731808813187148269gmail-p1" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(52,188,38)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures">diff --git a/Modules/Platform/Android/Determine-Compiler-NDK.cmake b/Modules/Platform/Android/Determine-Compiler-NDK.cmake</span></p><p class="gmail-m_8731808813187148269gmail-p2" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(213,59,211)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures">index 5f2cc524e5..c211bbceee 100644</span></p><p class="gmail-m_8731808813187148269gmail-p1" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(52,188,38)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures">--- a/Modules/Platform/Android/Determine-Compiler-NDK.cmake</span></p><p class="gmail-m_8731808813187148269gmail-p1" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(52,188,38)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures">+++ b/Modules/Platform/Android/Determine-Compiler-NDK.cmake</span></p><p class="gmail-m_8731808813187148269gmail-p2" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(213,59,211)"><span class="gmail-m_8731808813187148269gmail-s2" style="font-variant-ligatures:no-common-ligatures;color:rgb(205,121,35)">@@ -239,7 +239,7 @@</span><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures"> set(_ANDROID_TOOL_CXX_TOOLCHAIN_SUFFIX "${_ANDROID_TOOL_C_TOOLCHAIN_SUFFIX}")</span></p><p class="gmail-m_8731808813187148269gmail-p3" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(0,0,0)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures"><span class="gmail-m_8731808813187148269gmail-Apple-converted-space"> </span>if(_ANDROID_TOOL_CLANG_NAME)</span></p><p class="gmail-m_8731808813187148269gmail-p3" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(0,0,0)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures"><span class="gmail-m_8731808813187148269gmail-Apple-converted-space">   </span>message(STATUS "Android: Selected Clang toolchain '${_ANDROID_TOOL_CLANG_NAME}' with GCC toolchain '${_ANDROID_TOOL_NAME}'")</span></p><p class="gmail-m_8731808813187148269gmail-p3" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(0,0,0)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures"><span class="gmail-m_8731808813187148269gmail-Apple-converted-space">   </span>set(_ANDROID_TOOL_C_COMPILER "${CMAKE_ANDROID_NDK}/toolchains/${_ANDROID_TOOL_LLVM_NAME}/prebuilt/${_ANDROID_HOST_DIR}/bin/clang${_ANDROID_HOST_EXT}")</span></p><p class="gmail-m_8731808813187148269gmail-p2" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(213,59,211)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures">-<span class="gmail-m_8731808813187148269gmail-Apple-converted-space">  </span>set(_ANDROID_TOOL_C_COMPILER_EXTERNAL_TOOLCHAIN ${CMAKE_ANDROID_NDK}/toolchains/${_ANDROID_TOOL_NAME}/prebuilt/${_ANDROID_HOST_DIR})</span></p><p class="gmail-m_8731808813187148269gmail-p4" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(51,187,200)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures">+<span class="gmail-m_8731808813187148269gmail-Apple-converted-space">  </span>set(_ANDROID_TOOL_C_COMPILER_EXTERNAL_TOOLCHAIN ${CMAKE_ANDROID_NDK}/toolchains/${_ANDROID_TOOL_LLVM_NAME}/prebuilt/${_ANDROID_HOST_DIR})</span></p><p class="gmail-m_8731808813187148269gmail-p3" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(0,0,0)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures"><span class="gmail-m_8731808813187148269gmail-Apple-converted-space">   </span>set(_ANDROID_TOOL_CXX_COMPILER "${CMAKE_ANDROID_NDK}/toolchains/${_ANDROID_TOOL_LLVM_NAME}/prebuilt/${_ANDROID_HOST_DIR}/bin/clang++${_ANDROID_HOST_EXT}")</span></p><p class="gmail-m_8731808813187148269gmail-p3" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(0,0,0)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures"><span class="gmail-m_8731808813187148269gmail-Apple-converted-space">   </span>set(_ANDROID_TOOL_CXX_COMPILER_EXTERNAL_TOOLCHAIN "${_ANDROID_TOOL_C_COMPILER_EXTERNAL_TOOLCHAIN}")</span></p><p class="gmail-m_8731808813187148269gmail-p3" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(0,0,0)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures"><span class="gmail-m_8731808813187148269gmail-Apple-converted-space"> </span>else()</span></p><p class="gmail-m_8731808813187148269gmail-p3" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(0,0,0)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures"><br></span></p><p class="gmail-m_8731808813187148269gmail-p3" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;line-height:normal;color:rgb(0,0,0)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures"><font face="arial, helvetica, sans-serif">The reason seems to be that if ANDROID_TOOL_NAME contains -clang, it is set to the empty string on line 120 (CMake 10.13), so the external toolchain path contains an empty directory element (//). ANDROID_TOOL_LLVM_NAME contains "llvm", which is the correct string to make the above path correct on my installation.</font></span></p><p class="gmail-m_8731808813187148269gmail-p3" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;line-height:normal;color:rgb(0,0,0)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures"><font face="arial, helvetica, sans-serif"><br></font></span></p><p class="gmail-m_8731808813187148269gmail-p3" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;line-height:normal;color:rgb(0,0,0)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures"><font face="arial, helvetica, sans-serif">If I'm doing something wrong and there's a better way to do this which doesn't require patching CMake, please let me know.</font></span></p><p class="gmail-m_8731808813187148269gmail-p3" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;line-height:normal;color:rgb(0,0,0)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures"><font face="arial, helvetica, sans-serif"><br></font></span></p><p class="gmail-m_8731808813187148269gmail-p3" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;line-height:normal;color:rgb(0,0,0)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures"><font face="arial, helvetica, sans-serif">Thanks,</font></span></p><p class="gmail-m_8731808813187148269gmail-p3" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;line-height:normal;color:rgb(0,0,0)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures"><font face="arial, helvetica, sans-serif"><br></font></span></p><p class="gmail-m_8731808813187148269gmail-p3" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;line-height:normal;color:rgb(0,0,0)"><span class="gmail-m_8731808813187148269gmail-s1" style="font-variant-ligatures:no-common-ligatures"><font face="arial, helvetica, sans-serif">Stephen</font></span></p></div></div>