Add compiler target compile options.

For clang, this allows passing -target <triple> to the compiler, and
for qcc, -V<arch> using toolchain files containing something like

 set(triple arm-linux-gnueabihf)
 set(CMAKE_C_COMPILER "/usr/bin/clang")
 set(CMAKE_C_COMPILER_TARGET ${triple})
 set(CMAKE_CXX_COMPILER "/usr/bin/clang++")
 set(CMAKE_CXX_COMPILER_TARGET ${triple})

or

 set(arch gcc_ntoarmv7le)
 set(CMAKE_C_COMPILER /opt/qnx650/host/linux/x86/usr/bin/qcc)
 set(CMAKE_C_COMPILER_TARGET ${arch})
 set(CMAKE_CXX_COMPILER /opt/qnx650/host/linux/x86/usr/bin/QCC)
 set(CMAKE_CXX_COMPILER_TARGET ${arch})

Both clang and qcc are inherently cross compiler( driver)s.

When cross-compiling with clang, use the CMAKE_${lang}_COMPILER_TARGET
as the _CMAKE_TOOLCHAIN_PREFIX to find the appropriate binutils.

When cross-compiling with QNX qcc, use the CMAKE_${lang}_COMPILER_TARGET
to set the appropriate _CMAKE_TOOLCHAIN_PREFIX.

Help/manual/cmake-variables.7.rst

@@ -234,6 +234,7 @@ Variables for Languages
    /variable/CMAKE_LANG_COMPILER_ID
    /variable/CMAKE_LANG_COMPILER_LOADED
    /variable/CMAKE_LANG_COMPILER
+   /variable/CMAKE_LANG_COMPILER_TARGET
    /variable/CMAKE_LANG_COMPILER_VERSION
    /variable/CMAKE_LANG_CREATE_SHARED_LIBRARY
    /variable/CMAKE_LANG_CREATE_SHARED_MODULE

Help/variable/CMAKE_LANG_COMPILER_TARGET.rst

@@ -0,0 +1,11 @@
+CMAKE_<LANG>_COMPILER_TARGET
+----------------------------
+
+The target for cross-compiling, if supported.
+
+Some compiler drivers are inherently cross-compilers, such as clang and
+QNX qcc. These compiler drivers support a command-line argument to specify
+the target to cross-compile for.
+
+This variable may only be set in a toolchain file specified by
+the ``CMAKE_TOOLCHAIN_FILE`` variable.

Modules/CMakeDetermineCCompiler.cmake

@@ -158,6 +158,12 @@ if (CMAKE_CROSSCOMPILING  AND NOT _CMAKE_TOOLCHAIN_PREFIX)
     get_filename_component(COMPILER_BASENAME "${CMAKE_C_COMPILER}" NAME)
     if (COMPILER_BASENAME MATCHES "^(.+-)(clang|g?cc)(-[0-9]+\\.[0-9]+\\.[0-9]+)?(\\.exe)?$")
       set(_CMAKE_TOOLCHAIN_PREFIX ${CMAKE_MATCH_1})
+    elseif("${CMAKE_C_COMPILER_ID}" MATCHES "Clang")
+      set(_CMAKE_TOOLCHAIN_PREFIX ${CMAKE_C_COMPILER_TARGET}-)
+    elseif(COMPILER_BASENAME MATCHES "qcc(\\.exe)?$")
+      if(CMAKE_C_COMPILER_TARGET MATCHES "gcc_nto([^_le]+)(le)?.*$")
+        set(_CMAKE_TOOLCHAIN_PREFIX nto${CMAKE_MATCH_1}-)
+      endif()
     endif ()
 
     # if "llvm-" is part of the prefix, remove it, since llvm doesn't have its own binutils

Modules/CMakeDetermineCXXCompiler.cmake

@@ -156,6 +156,12 @@ if (CMAKE_CROSSCOMPILING  AND NOT  _CMAKE_TOOLCHAIN_PREFIX)
     get_filename_component(COMPILER_BASENAME "${CMAKE_CXX_COMPILER}" NAME)
     if (COMPILER_BASENAME MATCHES "^(.+-)(clan)?[gc]\\+\\+(-[0-9]+\\.[0-9]+\\.[0-9]+)?(\\.exe)?$")
       set(_CMAKE_TOOLCHAIN_PREFIX ${CMAKE_MATCH_1})
+    elseif("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
+      set(_CMAKE_TOOLCHAIN_PREFIX ${CMAKE_CXX_COMPILER_TARGET}-)
+    elseif(COMPILER_BASENAME MATCHES "QCC(\\.exe)?$")
+      if(CMAKE_CXX_COMPILER_TARGET MATCHES "gcc_nto([^_le]+)(le)?.*$")
+        set(_CMAKE_TOOLCHAIN_PREFIX nto${CMAKE_MATCH_1}-)
+      endif()
     endif ()
 
     # if "llvm-" is part of the prefix, remove it, since llvm doesn't have its own binutils

Modules/Compiler/Clang.cmake

@@ -30,5 +30,6 @@ else()
     set(CMAKE_${lang}_COMPILE_OPTIONS_PIE "-fPIE")
     set(CMAKE_INCLUDE_SYSTEM_FLAG_${lang} "-isystem ")
     set(CMAKE_${lang}_COMPILE_OPTIONS_VISIBILITY "-fvisibility=")
+    set(CMAKE_${lang}_COMPILE_OPTIONS_TARGET "-target ")
   endmacro()
 endif()

Modules/Platform/QNX.cmake

@@ -16,6 +16,9 @@ set(CMAKE_SHARED_LIBRARY_RUNTIME_C_FLAG_SEP ":")
 set(CMAKE_SHARED_LIBRARY_RPATH_LINK_C_FLAG "-Wl,-rpath-link,")
 set(CMAKE_SHARED_LIBRARY_SONAME_C_FLAG "-Wl,-soname,")
 set(CMAKE_EXE_EXPORTS_C_FLAG "-Wl,--export-dynamic")
+# http://www.qnx.com/developers/docs/6.4.0/neutrino/utilities/q/qcc.html#examples
+set(CMAKE_C_COMPILE_OPTIONS_TARGET "-V")
+set(CMAKE_CXX_COMPILE_OPTIONS_TARGET "-V")
 
 # Shared libraries with no builtin soname may not be linked safely by
 # specifying the file path.

Source/cmCoreTryCompile.cxx

@@ -405,6 +405,20 @@ int cmCoreTryCompile::TryCompileCode(std::vector<std::string> const& argv)
       flag += this->Makefile->GetSafeDefinition("CMAKE_OSX_DEPLOYMENT_TARGET");
       cmakeFlags.push_back(flag);
       }
+    if (const char *cxxDef
+              = this->Makefile->GetDefinition("CMAKE_CXX_COMPILER_TARGET"))
+      {
+      std::string flag="-DCMAKE_CXX_COMPILER_TARGET=";
+      flag += cxxDef;
+      cmakeFlags.push_back(flag);
+      }
+    if (const char *cDef
+                = this->Makefile->GetDefinition("CMAKE_C_COMPILER_TARGET"))
+      {
+      std::string flag="-DCMAKE_C_COMPILER_TARGET=";
+      flag += cDef;
+      cmakeFlags.push_back(flag);
+      }
     if(this->Makefile->GetDefinition("CMAKE_POSITION_INDEPENDENT_CODE")!=0)
       {
       fprintf(fout, "set(CMAKE_POSITION_INDEPENDENT_CODE \"ON\")\n");

Source/cmLocalGenerator.cxx

@@ -1043,11 +1043,20 @@ cmLocalGenerator::ExpandRuleVariable(std::string const& variable,
       // If this is the compiler then look for the extra variable
       // _COMPILER_ARG1 which must be the first argument to the compiler
       const char* compilerArg1 = 0;
+      const char* compilerTarget = 0;
+      const char* compilerOptionTarget = 0;
       if(actualReplace == "CMAKE_${LANG}_COMPILER")
         {
         std::string arg1 = actualReplace + "_ARG1";
         cmSystemTools::ReplaceString(arg1, "${LANG}", lang);
         compilerArg1 = this->Makefile->GetDefinition(arg1.c_str());
+        compilerTarget
+              = this->Makefile->GetDefinition(
+                (std::string("CMAKE_") + lang + "_COMPILER_TARGET").c_str());
+        compilerOptionTarget
+              = this->Makefile->GetDefinition(
+                (std::string("CMAKE_") + lang +
+                                          "_COMPILE_OPTIONS_TARGET").c_str());
         }
       if(actualReplace.find("${LANG}") != actualReplace.npos)
         {
@@ -1068,6 +1077,12 @@ cmLocalGenerator::ExpandRuleVariable(std::string const& variable,
             ret += " ";
             ret += compilerArg1;
             }
+          if (compilerTarget && compilerOptionTarget)
+            {
+            ret += " ";
+            ret += compilerOptionTarget;
+            ret += compilerTarget;
+            }
           return ret;
           }
         return replace;