Reorganize as modern CMake with an interface target

CMakeLists.txt

@@ -1,32 +1,60 @@
+# Peglib is a header-only library with zero dependencies (pthreads on Linux).
+#
+# To build with it, add the CppPegLib INTERFACE in your cmake lists, this will
+# provide the neccessary include paths, linkage, etc.
+#
+# Then your code simply needs to #include <peglib.h>
+
 cmake_minimum_required(VERSION 3.14)
-project(cpp-peglib)
 
-set(CMAKE_CXX_STANDARD 17)
-set(CMAKE_CXX_EXTENSIONS OFF)
+project(cpp-peglib DESCRIPTION "C++17 header-only PEG library" LANGUAGES CXX)
 
-if(MSVC)
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /Zc:__cplusplus /utf-8 /D_CRT_SECURE_NO_DEPRECATE")
-else()
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra")
-endif()
+include(cmake/PeglibCXXStandard.cmake)
+include(cmake/PeglibOptions.cmake)
+
+add_library(
+  CppPegLib
+
+  INTERFACE
+
+  peglib.h
+)
+
+# Tag the library with the path to the top of it's source tree.
+set_target_properties(CppPegLib PROPERTIES SOURCE_FOLDER ${CMAKE_CURRENT_LIST_DIR})
 
-option(PEGLIB_BUILD_TESTS "Build cpp-peglib tests" ON)
+# Include cmake helpers that attach other properties to the target.
+include(cmake/PeglibCompileOptions.cmake)
+include(cmake/PeglibIncludePaths.cmake)
+include(cmake/PeglibThreads.cmake)
 
-set(THREADS_PREFER_PTHREAD_FLAG ON)
-find_package(Threads)
 
-if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
-  set(add_link_deps Threads::Threads)
+if(PEGLIB_BUILD_LINTER)
+  add_subdirectory(lint)
+else()
+  message(STATUS "PEGLIB_BUILD_LINTER is OFF: Not building linter")
 endif()
 
-add_subdirectory(lint)
 
-add_subdirectory(example)
+if(PEGLIB_BUILD_EXAMPLES)
+  add_subdirectory(example)
+else()
+  message(STATUS "PEGLIB_BUILD_EXAMPLES is OFF: Not building examples")
+endif ()
+
 # add_subdirectory(cymbol)
 
-if (${PEGLIB_BUILD_TESTS})
+
+if (PEGLIB_BUILD_TESTS)
+  include(CTest)
   add_subdirectory(test)
   enable_testing()
+else()
+  message(STATUS "PEGLIB_BUILD_TESTS is OFF: Skipping tests")
 endif()
 
+
+# This facilitates users who want to install this system-wide, but they'll have the
+# complication of needing to set the compile flags and potentially link flag.
+# Might be worth telling CMake how to generate a config when installing.
 install(FILES peglib.h DESTINATION include)

cmake/PeglibCXXStandard.cmake

@@ -0,0 +1,6 @@
+include_guard(GLOBAL)
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_EXTENSIONS OFF)
+

cmake/PeglibOptions.cmake

@@ -0,0 +1,15 @@
+include_guard(GLOBAL)
+
+# Only default ot building tests and examples when building standalone, which
+# we can determine by whether the top of the build tree is this folder or not.
+if(CMAKE_SOURCE_DIR STREQUAL "${CMAKE_CURRENT_SOURCE_DIR}")
+  set(_standalone_build ON)
+else()
+  set(_standalone_build OFF)
+endif()
+
+option(PEGLIB_BUILD_LINTER   "Build peglib's linter"  ${_standalone_build})
+option(PEGLIB_BUILD_TESTS    "Build cpp-peglib tests" ${_standalone_build})
+option(PEGLIB_BUILD_EXAMPLES "Build example parsers"  ${_standalone_build})
+
+unset(_standalone_build)

cmake/PeglibThreads.cmake

@@ -0,0 +1,13 @@
+include_guard(GLOBAL)
+
+# We don't really have any dependencies, except needing to link against the
+# pthreads library on linu.x
+if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
+  set(THREADS_PREFER_PTHREAD_FLAG ON)
+
+  find_package(Threads REQUIRED)
+
+  target_compile_options(CppPegLib "-pthread")
+  target_link_libraries(CppPegLib Threads::Threads)
+endif()
+

example/CMakeLists.txt

@@ -1,22 +1,20 @@
 cmake_minimum_required(VERSION 3.14)
 project(example)
 
-include_directories(..)
-
 add_executable(calc calc.cc)
-target_link_libraries(calc ${add_link_deps})
+target_link_libraries(calc CppPegLib)
 
 add_executable(calc2 calc2.cc)
-target_link_libraries(calc2 ${add_link_deps})
+target_link_libraries(calc2 CppPegLib)
 
 add_executable(calc3 calc3.cc)
-target_link_libraries(calc3 ${add_link_deps})
+target_link_libraries(calc3 CppPegLib)
 
 add_executable(calc4 calc4.cc)
-target_link_libraries(calc4 ${add_link_deps})
+target_link_libraries(calc4 CppPegLib)
 
 add_executable(calc5 calc5.cc)
-target_link_libraries(calc5 ${add_link_deps})
+target_link_libraries(calc5 CppPegLib)
 
 add_executable(indent indent.cc)
-target_link_libraries(indent ${add_link_deps})
+target_link_libraries(indent CppPegLib)

lint/CMakeLists.txt

@@ -1,7 +1,6 @@
 cmake_minimum_required(VERSION 3.14)
 project(peglint)
 
-include_directories(..)
-
 add_executable(peglint peglint.cc)
-target_link_libraries(peglint ${add_link_deps})
+
+target_link_libraries(peglint CppPegLib)

pl0/CMakeLists.txt

@@ -1,10 +1,7 @@
 /Users/yhirose/Projects/cpp-peglib/.travis.yml
 project(pl0)
 
-include_directories(..)
-
 add_executable(pl0 pl0.cc)
 find_package(LLVM REQUIRED CONFIG)
-set(add_link_deps ${add_link_deps} LLVM)
 target_include_directories(pl0 PUBLIC ${LLVM_INCLUDE_DIRS})
-target_link_libraries(pl0 ${add_link_deps})
+target_link_libraries(pl0 CppPegLib LLVM)

test/CMakeLists.txt

@@ -14,8 +14,7 @@ enable_testing()
 
 add_executable(test-main test1.cc test2.cc test3.cc)
 
-target_include_directories(test-main PRIVATE ..)
-
 include(GoogleTest)
 gtest_discover_tests(test-main)
+target_link_libraries(test-main PUBLIC CppPegLib)
 target_link_libraries(test-main PRIVATE gtest_main)