try_compile: Add option to control type of target

Create a `CMAKE_TRY_COMPILE_TARGET_TYPE` option to specify use
of `add_library(... STATIC ...)` for the generated test project.
This will be useful for cross-compiling toolchains that cannot
link a binary without custom flags or scripts.

Help/command/try_compile.rst

@@ -112,3 +112,6 @@ The current setting of :policy:`CMP0065` is set in the generated project.
 
 Set the :variable:`CMAKE_TRY_COMPILE_CONFIGURATION` variable to choose
 a build configuration.
+
+Set the :variable:`CMAKE_TRY_COMPILE_TARGET_TYPE` variable to specify
+the type of target used for the source file signature.

Help/manual/cmake-variables.7.rst

@@ -292,6 +292,7 @@ Variables that Control the Build
    /variable/CMAKE_STATIC_LINKER_FLAGS_CONFIG
    /variable/CMAKE_STATIC_LINKER_FLAGS
    /variable/CMAKE_TRY_COMPILE_CONFIGURATION
+   /variable/CMAKE_TRY_COMPILE_TARGET_TYPE
    /variable/CMAKE_USE_RELATIVE_PATHS
    /variable/CMAKE_VISIBILITY_INLINES_HIDDEN
    /variable/CMAKE_VS_INCLUDE_INSTALL_TO_DEFAULT_BUILD

Help/release/dev/try_compile-target-type.rst

@@ -0,0 +1,8 @@
+try_compile-target-type
+-----------------------
+
+* The :command:`try_compile` command learned to check a new
+  :variable:`CMAKE_TRY_COMPILE_TARGET_TYPE` variable to optionally
+  build a static library instead of an executable.  This is useful
+  for cross-compiling toolchains that cannot link binaries without
+  custom flags or scripts.

Help/variable/CMAKE_TRY_COMPILE_TARGET_TYPE.rst

@@ -0,0 +1,15 @@
+CMAKE_TRY_COMPILE_TARGET_TYPE
+-----------------------------
+
+Type of target generated for :command:`try_compile` calls using the
+source file signature.  Valid values are:
+
+``EXECUTABLE``
+  Use :command:`add_executable` to name the source file in the
+  generated project.  This is the default if no value is given.
+
+``STATIC_LIBRARY``
+  Use :command:`add_library` with the ``STATIC`` option to name the
+  source file in the generated project.  This avoids running the
+  linker and is intended for use with cross-compiling toolchains
+  that cannot link without custom flags or linker scripts.

Source/cmCoreTryCompile.cxx

@@ -19,13 +19,42 @@
 
 #include <assert.h>
 
-int cmCoreTryCompile::TryCompileCode(std::vector<std::string> const& argv)
+int cmCoreTryCompile::TryCompileCode(std::vector<std::string> const& argv,
+                                     bool isTryRun)
 {
   this->BinaryDirectory = argv[1].c_str();
   this->OutputFile = "";
   // which signature were we called with ?
   this->SrcFileSignature = true;
 
+  cmState::TargetType targetType = cmState::EXECUTABLE;
+  const char* tt =
+    this->Makefile->GetDefinition("CMAKE_TRY_COMPILE_TARGET_TYPE");
+  if (!isTryRun && tt && *tt)
+    {
+    if (strcmp(tt, cmState::GetTargetTypeName(cmState::EXECUTABLE)) == 0)
+      {
+      targetType = cmState::EXECUTABLE;
+      }
+    else if (strcmp(tt,
+                    cmState::GetTargetTypeName(cmState::STATIC_LIBRARY)) == 0)
+      {
+      targetType = cmState::STATIC_LIBRARY;
+      }
+    else
+      {
+      this->Makefile->IssueMessage(
+        cmake::FATAL_ERROR,
+        std::string("Invalid value '") + tt + "' for "
+        "CMAKE_TRY_COMPILE_TARGET_TYPE.  Only "
+        "'" + cmState::GetTargetTypeName(cmState::EXECUTABLE) + "' and "
+        "'" + cmState::GetTargetTypeName(cmState::STATIC_LIBRARY) + "' "
+        "are allowed."
+        );
+      return -1;
+      }
+    }
+
   const char* sourceDirectory = argv[2].c_str();
   const char* projectName = 0;
   std::string targetName;
@@ -486,11 +515,22 @@ int cmCoreTryCompile::TryCompileCode(std::vector<std::string> const& argv)
       fprintf(fout, "set(CMAKE_ENABLE_EXPORTS %s)\n", ee);
       }
 
-    /* Put the executable at a known location (for COPY_FILE).  */
-    fprintf(fout, "set(CMAKE_RUNTIME_OUTPUT_DIRECTORY \"%s\")\n",
-            this->BinaryDirectory.c_str());
-    /* Create the actual executable.  */
-    fprintf(fout, "add_executable(%s", targetName.c_str());
+    if (targetType == cmState::EXECUTABLE)
+      {
+      /* Put the executable at a known location (for COPY_FILE).  */
+      fprintf(fout, "set(CMAKE_RUNTIME_OUTPUT_DIRECTORY \"%s\")\n",
+              this->BinaryDirectory.c_str());
+      /* Create the actual executable.  */
+      fprintf(fout, "add_executable(%s", targetName.c_str());
+      }
+    else // if (targetType == cmState::STATIC_LIBRARY)
+      {
+      /* Put the static library at a known location (for COPY_FILE).  */
+      fprintf(fout, "set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY \"%s\")\n",
+              this->BinaryDirectory.c_str());
+      /* Create the actual static library.  */
+      fprintf(fout, "add_library(%s STATIC", targetName.c_str());
+      }
     for(std::vector<std::string>::iterator si = sources.begin();
         si != sources.end(); ++si)
       {
@@ -549,7 +589,7 @@ int cmCoreTryCompile::TryCompileCode(std::vector<std::string> const& argv)
   if (this->SrcFileSignature)
     {
     std::string copyFileErrorMessage;
-    this->FindOutputFile(targetName);
+    this->FindOutputFile(targetName, targetType);
 
     if ((res==0) && !copyFile.empty())
       {
@@ -651,13 +691,26 @@ void cmCoreTryCompile::CleanupFiles(const char* binDir)
     }
 }
 
-void cmCoreTryCompile::FindOutputFile(const std::string& targetName)
+void cmCoreTryCompile::FindOutputFile(const std::string& targetName,
+                                      cmState::TargetType targetType)
 {
   this->FindErrorMessage = "";
   this->OutputFile = "";
   std::string tmpOutputFile = "/";
-  tmpOutputFile += targetName;
-  tmpOutputFile +=this->Makefile->GetSafeDefinition("CMAKE_EXECUTABLE_SUFFIX");
+  if (targetType == cmState::EXECUTABLE)
+    {
+    tmpOutputFile += targetName;
+    tmpOutputFile +=
+      this->Makefile->GetSafeDefinition("CMAKE_EXECUTABLE_SUFFIX");
+    }
+  else // if (targetType == cmState::STATIC_LIBRARY)
+    {
+    tmpOutputFile +=
+      this->Makefile->GetSafeDefinition("CMAKE_STATIC_LIBRARY_PREFIX");
+    tmpOutputFile += targetName;
+    tmpOutputFile +=
+      this->Makefile->GetSafeDefinition("CMAKE_STATIC_LIBRARY_SUFFIX");
+    }
 
   // a list of directories where to search for the compilation result
   // at first directly in the binary dir

Source/cmCoreTryCompile.h

@@ -30,7 +30,7 @@ public:
    * commands, such as TryRun can access the same logic without
    * duplication.
    */
-  int TryCompileCode(std::vector<std::string> const& argv);
+  int TryCompileCode(std::vector<std::string> const& argv, bool isTryRun);
 
   /**
    * This deletes all the files created by TryCompileCode.
@@ -44,8 +44,8 @@ public:
   TryCompileCode. The result is stored in OutputFile. If nothing is found,
   the error message is stored in FindErrorMessage.
    */
-  void FindOutputFile(const std::string& targetName);
-
+  void FindOutputFile(const std::string& targetName,
+                      cmState::TargetType targetType);
 
   cmTypeMacro(cmCoreTryCompile, cmCommand);
 

Source/cmTryCompileCommand.cxx

@@ -28,7 +28,7 @@ bool cmTryCompileCommand
     return false;
     }
 
-  this->TryCompileCode(argv);
+  this->TryCompileCode(argv, false);
 
   // if They specified clean then we clean up what we can
   if (this->SrcFileSignature)

Source/cmTryRunCommand.cxx

@@ -135,7 +135,7 @@ bool cmTryRunCommand
   this->CompileResultVariable = argv[1];
 
   // do the try compile
-  int res = this->TryCompileCode(tryCompile);
+  int res = this->TryCompileCode(tryCompile, true);
 
   // now try running the command if it compiled
   if (!res)

Tests/RunCMake/try_compile/RunCMakeTest.cmake

@@ -16,6 +16,10 @@ run_cmake(BadSources2)
 run_cmake(NonSourceCopyFile)
 run_cmake(NonSourceCompileDefinitions)
 
+run_cmake(TargetTypeExe)
+run_cmake(TargetTypeInvalid)
+run_cmake(TargetTypeStatic)
+
 run_cmake(CMP0056)
 
 if(RunCMake_GENERATOR MATCHES "Make|Ninja")

Tests/RunCMake/try_compile/TargetTypeExe.cmake

@@ -0,0 +1,14 @@
+enable_language(C)
+set(CMAKE_TRY_COMPILE_TARGET_TYPE EXECUTABLE)
+try_compile(result ${CMAKE_CURRENT_BINARY_DIR}
+  SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/src.c
+  OUTPUT_VARIABLE out
+  COPY_FILE ${CMAKE_CURRENT_BINARY_DIR}/copy
+  COPY_FILE_ERROR copy_err
+  )
+if(NOT result)
+  message(FATAL_ERROR "try_compile failed:\n${out}")
+endif()
+if(copy_err)
+  message(FATAL_ERROR "try_compile COPY_FILE failed:\n${copy_err}")
+endif()

Tests/RunCMake/try_compile/TargetTypeInvalid-result.txt

@@ -0,0 +1 @@
+1

Tests/RunCMake/try_compile/TargetTypeInvalid-stderr.txt

@@ -0,0 +1,5 @@
+^CMake Error at TargetTypeInvalid.cmake:2 \(try_compile\):
+  Invalid value 'INVALID' for CMAKE_TRY_COMPILE_TARGET_TYPE.  Only
+  'EXECUTABLE' and 'STATIC_LIBRARY' are allowed.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)

Tests/RunCMake/try_compile/TargetTypeInvalid.cmake

@@ -0,0 +1,2 @@
+set(CMAKE_TRY_COMPILE_TARGET_TYPE INVALID)
+try_compile(result ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/src.c)

Tests/RunCMake/try_compile/TargetTypeStatic.cmake

@@ -0,0 +1,14 @@
+enable_language(C)
+set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
+try_compile(result ${CMAKE_CURRENT_BINARY_DIR}
+  SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/other.c
+  OUTPUT_VARIABLE out
+  COPY_FILE ${CMAKE_CURRENT_BINARY_DIR}/copy
+  COPY_FILE_ERROR copy_err
+  )
+if(NOT result)
+  message(FATAL_ERROR "try_compile failed:\n${out}")
+endif()
+if(copy_err)
+  message(FATAL_ERROR "try_compile COPY_FILE failed:\n${copy_err}")
+endif()

Tests/RunCMake/try_compile/other.c

@@ -0,0 +1 @@
+int other(void) { return 0; }