ENH: Prevent cmake in source builds

CMakeLists.txt

@@ -75,6 +75,9 @@ project(jsoncpp
 message(STATUS "JsonCpp Version: ${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}.${PROJECT_VERSION_PATCH}")
 set(PROJECT_SOVERSION 24)
 
+include(${CMAKE_CURRENT_SOURCE_DIR}/include/PreventInSourceBuilds.cmake)
+include(${CMAKE_CURRENT_SOURCE_DIR}/include/PreventInBuildInstalls.cmake)
+
 option(JSONCPP_WITH_TESTS "Compile and (for jsoncpp_check) run JsonCpp test executables" ON)
 option(JSONCPP_WITH_POST_BUILD_UNITTEST "Automatically run unit-tests as a post build step" ON)
 option(JSONCPP_WITH_WARNING_AS_ERROR "Force compilation to fail if a warning occurs" OFF)

CONTRIBUTING.md

@@ -19,7 +19,7 @@ If you wish to install to a directory other than /usr/local, set an environment
     DESTDIR=/path/to/install/dir
 
 Then,
-
+```sh
     cd jsoncpp/
     BUILD_TYPE=debug
     #BUILD_TYPE=release
@@ -35,6 +35,7 @@ Then,
     #meson test --no-rebuild --print-errorlogs
 
     sudo ninja install
+```
 
 ## Building and testing with other build systems
 See https://github.com/open-source-parsers/jsoncpp/wiki/Building

appveyor.yml

@@ -1,6 +1,7 @@
 clone_folder: c:\projects\jsoncpp
 
 environment:
+
   matrix:
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
       CMAKE_GENERATOR: Visual Studio 14 2015
@@ -13,11 +14,15 @@ environment:
 
 build_script:
   - cmake --version
-  - cd c:\projects\jsoncpp
-  - cmake -G "%CMAKE_GENERATOR%" -DCMAKE_INSTALL_PREFIX:PATH=%CD:\=/%/install -DBUILD_SHARED_LIBS:BOOL=ON .
+  # The build script starts in root.
+  - set JSONCPP_FOLDER=%cd%
+  - set JSONCPP_BUILD_FOLDER=%JSONCPP_FOLDER%\build\release
+  - mkdir -p %JSONCPP_BUILD_FOLDER%
+  - cd %JSONCPP_BUILD_FOLDER%
+  - cmake -G "%CMAKE_GENERATOR%" -DCMAKE_INSTALL_PREFIX:PATH=%CD:\=/%/install -DBUILD_SHARED_LIBS:BOOL=ON %JSONCPP_FOLDER%
   # Use ctest to make a dashboard build:
   # - ctest -D Experimental(Start|Update|Configure|Build|Test|Coverage|MemCheck|Submit)
-  # NOTE: Testing on window is not yet finished:
+  # NOTE: Testing on windows is not yet finished:
   # - ctest -C Release -D ExperimentalStart -D ExperimentalConfigure -D ExperimentalBuild -D ExperimentalTest -D ExperimentalSubmit
   - ctest -C Release -D ExperimentalStart -D ExperimentalConfigure -D ExperimentalBuild -D ExperimentalSubmit
   # Final step is to verify that installation succeeds

include/PreventInBuildInstalls.cmake

@@ -0,0 +1,9 @@
+string(TOLOWER "${CMAKE_INSTALL_PREFIX}" _PREFIX)
+string(TOLOWER "${ITK_BINARY_DIR}" _BUILD)
+if("${_PREFIX}" STREQUAL "${_BUILD}")
+  message(FATAL_ERROR
+    "The current CMAKE_INSTALL_PREFIX points at the build tree:\n"
+    "  ${CMAKE_INSTALL_PREFIX}\n"
+    "This is not supported."
+    )
+endif()

include/PreventInSourceBuilds.cmake

@@ -0,0 +1,45 @@
+#
+# This function will prevent in-source builds
+function(AssureOutOfSourceBuilds)
+  # make sure the user doesn't play dirty with symlinks
+  get_filename_component(srcdir "${CMAKE_SOURCE_DIR}" REALPATH)
+  get_filename_component(bindir "${CMAKE_BINARY_DIR}" REALPATH)
+
+  # disallow in-source builds
+  if("${srcdir}" STREQUAL "${bindir}")
+    message("######################################################")
+    message("# jsoncpp should not be configured & built in the jsoncpp source directory")
+    message("# You must run cmake in a build directory.")
+    message("# For example:")
+    message("# mkdir jsoncpp-Sandbox ; cd jsoncpp-sandbox")
+    message("# git clone https://github.com/open-source-parsers/jsoncpp.git # or download & unpack the source tarball")
+    message("# mkdir jsoncpp-build")
+    message("# this will create the following directory structure")
+    message("#")
+    message("# jsoncpp-Sandbox")
+    message("#  +--jsoncpp")
+    message("#  +--jsoncpp-build")
+    message("#")
+    message("# Then you can proceed to configure and build")
+    message("# by using the following commands")
+    message("#")
+    message("# cd jsoncpp-build")
+    message("# cmake ../jsoncpp # or ccmake, or cmake-gui ")
+    message("# make")
+    message("#")
+    message("# NOTE: Given that you already tried to make an in-source build")
+    message("#       CMake have already created several files & directories")
+    message("#       in your source tree. run 'git status' to find them and")
+    message("#       remove them by doing:")
+    message("#")
+    message("#       cd jsoncpp-Sandbox/jsoncpp")
+    message("#       git clean -n -d")
+    message("#       git clean -f -d")
+    message("#       git checkout --")
+    message("#")
+    message("######################################################")
+    message(FATAL_ERROR "Quitting configuration")
+  endif()
+endfunction()
+
+AssureOutOfSourceBuilds()