build: cleanup CMake (#319)

* build: inline a variable

* build: use `LINKER_LANGUAGE` property for C++ runtime

Rather than explicitly name the C++ runtime, use the `LINKER_LANGUAGE`
property to use the driver to spell the C++ runtime appropriately.

* build: use CMake to control C standard

Rather than use compiler specific flags to control the language
standard, indicate to CMake the desired standard.

* build: use the correct variable

These flags are being applied to the *C* compiler, check the C compiler,
not the C++ compiler.

* build: loosen the compiler check

This loosens the compiler identifier check to enable matching AppleClang
which is the identifier for the Xcode compiler.

* build: hoist shared flags to top-level CMakeLists

This hoists the common shared flags handling to the top-level CMakeLists
from sub-layers.  This prevents the duplication of the handling.

* build: remove duplicated flags

This is unnecessary, `/TP` is forced on all MSVC builds, no need to
duplicate the flag for older versions.

* build: loosen C compiler identifier check

Loosen the check to a match rather than equality check, this allows it
to match AppleClang which is the identifier for the Apple vended clang
compiler part of Xcode.

* build: use `add_compile_options`

Use `add_compile_options` rather than modify `CMAKE_C_FLAGS`.  The
latter is meant to be only modified by the user, not the package
developer.

* build: hoist sanitizer flags to global state

This moves the CMAKE_C_FLAGS handling to the top-level and uses
`add_compile_options` rather than modifying the user controlled flags.

* build: hoist `-fvisibilty` flags to top-level

These are global settings, hoist them to the top level.

* build: hoist the debug flag handling

Use a generator expression and hoist the flag handling for the debug
build.

* build: hoist the profile flag handling

This is a global flag, hoist it to the top level and use
`add_compile_options` rather than modify the user controlled flags.

* build: remove incorrect variable handling

This seemed to be attempting to set the linker not the linker flags for
the profile configuration.  This variable is not used, do not set it.

* build: remove unused CMake includes

3 files changed, 40 insertions, 55 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d9488dd..0d90eb1 100755
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -12,6 +12,16 @@ option(CMARK_STATIC "Build static libcmark library" ON)
 option(CMARK_SHARED "Build shared libcmark library" ON)
 option(CMARK_LIB_FUZZER "Build libFuzzer fuzzing harness" OFF)
 
+if(NOT MSVC)
+  set(CMAKE_C_STANDARD 99)
+  set(CMAKE_C_STANDARD_REQUIRED YES)
+  set(CMAKE_C_EXTENSIONS NO)
+endif()
+
+# -fvisibility=hidden
+set(CMAKE_C_VISIBILITY_PRESET hidden)
+set(CMAKE_VISIBILITY_INLINES_HIDDEN 1)
+
 # The Linux modules distributed with CMake add "-rdynamic" to the build flags
 # which is incompatible with static linking under certain configurations.
 # Unsetting CMAKE_SHARED_LIBRARY_LINK_C_FLAGS ensures this does not happen.
@@ -19,6 +29,31 @@ if(CMARK_STATIC AND "${CMAKE_SYSTEM_NAME}" STREQUAL "Linux")
   SET(CMAKE_SHARED_LIBRARY_LINK_C_FLAGS)
 endif()
 
+# Compiler flags
+if(MSVC)
+  # Force to always compile with W4
+  add_compile_options($<$<COMPILE_LANGUAGE:C>:/W4>)
+  add_compile_options($<$<COMPILE_LANGUAGE:C>:/wd4706>)
+  add_compile_options($<$<COMPILE_LANGUAGE:C>:/TP>)
+  add_compile_definitions($<$<COMPILE_LANGUAGE:C>:/D_CRT_SECURE_NO_WARNINGS>)
+elseif(CMAKE_COMPILER_IS_GNUCC OR CMAKE_C_COMPILER_ID MATCHES Clang)
+  add_compile_options($<$<COMPILE_LANGUAGE:C>:-Wall>)
+  add_compile_options($<$<COMPILE_LANGUAGE:C>:-Wextra>)
+  add_compile_options($<$<COMPILE_LANGUAGE:C>:-pedantic>)
+endif()
+
+# Check integrity of node structure when compiled as debug
+add_compile_definitions($<$<CONFIG:Debug>:CMARK_DEBUG_NODES>)
+
+add_compile_options($<$<AND:$<CONFIG:PROFILE>,$<COMPILE_LANGUAGE:C>>:-pg>)
+
+if(CMAKE_BUILD_TYPE STREQUAL Ubsan)
+  add_compile_options($<$<COMPILE_LANGUAGE:C>:-fsanitize=undefined>)
+endif()
+if(CMARK_LIB_FUZZER)
+  add_compile_options($<$<COMPILE_LANGUAGE:C>:-fsanitize-coverage=trace-pc-guard>)
+endif()
+
 add_subdirectory(src)
 if(CMARK_TESTS AND (CMARK_SHARED OR CMARK_STATIC))
   add_subdirectory(api_test)
diff --git a/api_test/CMakeLists.txt b/api_test/CMakeLists.txt
index 2701abb..b1c8499 100644
--- a/api_test/CMakeLists.txt
+++ b/api_test/CMakeLists.txt
@@ -13,17 +13,3 @@ if(CMARK_SHARED)
 else()
   target_link_libraries(api_test libcmark_static)
 endif()
-
-# Compiler flags
-if(MSVC)
-  # Force to always compile with W4
-  if(CMAKE_CXX_FLAGS MATCHES "/W[0-4]")
-    string(REGEX REPLACE "/W[0-4]" "/W4" CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
-  else()
-    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /W4")
-  endif()
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /wd4706 /D_CRT_SECURE_NO_WARNINGS")
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /TP")
-elseif(CMAKE_COMPILER_IS_GNUCC OR "${CMAKE_C_COMPILER_ID}" STREQUAL "Clang")
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -Wextra -std=c99 -pedantic")
-endif()
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 0aa0ee2..5171cde 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -66,17 +66,6 @@ elseif (CMARK_SHARED)
   target_link_libraries(${PROGRAM} ${LIBRARY})
 endif()
 
-# Check integrity of node structure when compiled as debug:
-set(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -DCMARK_DEBUG_NODES")
-set(CMAKE_LINKER_DEBUG "${CMAKE_LINKER_FLAGS_DEBUG}")
-
-set(CMAKE_C_FLAGS_PROFILE "${CMAKE_C_FLAGS_RELEASE} -pg")
-set(CMAKE_LINKER_PROFILE "${CMAKE_LINKER_FLAGS_RELEASE} -pg")
-
-# -fvisibility=hidden
-set(CMAKE_C_VISIBILITY_PRESET hidden)
-set(CMAKE_VISIBILITY_INLINES_HIDDEN 1)
-
 if (CMARK_SHARED)
   add_library(${LIBRARY} SHARED ${LIBRARY_SOURCES})
   # Include minor version and patch level in soname for now.
@@ -159,8 +148,6 @@ endif()
 # Feature tests
 include(CheckIncludeFile)
 include(CheckCSourceCompiles)
-include(CheckCSourceRuns)
-include(CheckSymbolExists)
 CHECK_INCLUDE_FILE(stdbool.h HAVE_STDBOOL_H)
 CHECK_C_SOURCE_COMPILES(
   "int main() { __builtin_expect(0,0); return 0; }"
@@ -174,35 +161,12 @@ CONFIGURE_FILE(
   ${CMAKE_CURRENT_SOURCE_DIR}/config.h.in
   ${CMAKE_CURRENT_BINARY_DIR}/config.h)
 
-# Always compile with warnings
-if(MSVC)
-  # Force to always compile with W4
-  if(CMAKE_CXX_FLAGS MATCHES "/W[0-4]")
-    string(REGEX REPLACE "/W[0-4]" "/W4" CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
-  else()
-    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /W4")
-  endif()
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /wd4706 /D_CRT_SECURE_NO_WARNINGS")
-elseif(CMAKE_COMPILER_IS_GNUCC OR "${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -Wextra -std=c99 -pedantic")
-endif()
-
-# Compile as C++ under MSVC older than 12.0
-if(MSVC AND MSVC_VERSION LESS 1800)
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /TP")
-endif()
-
-if(CMAKE_BUILD_TYPE STREQUAL "Ubsan")
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fsanitize=undefined")
-endif()
-
 if(CMARK_LIB_FUZZER)
-  set(FUZZ_HARNESS "cmark-fuzz")
-  add_executable(${FUZZ_HARNESS} ../test/cmark-fuzz.c ${LIBRARY_SOURCES})
-  target_link_libraries(${FUZZ_HARNESS} "${CMAKE_LIB_FUZZER_PATH}")
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fsanitize-coverage=trace-pc-guard")
+  add_executable(cmark-fuzz ../test/cmark-fuzz.c ${LIBRARY_SOURCES})
+  target_link_libraries(cmark-fuzz "${CMAKE_LIB_FUZZER_PATH}")
 
   # cmark is written in C but the libFuzzer runtime is written in C++ which
-  # needs to link against the C++ runtime. Explicitly link it into cmark-fuzz
-  set_target_properties(${FUZZ_HARNESS} PROPERTIES LINK_FLAGS "-lstdc++")
+  # needs to link against the C++ runtime.
+  set_target_properties(cmark-fuzz PROPERTIES
+    LINKER_LANGUAGE CXX)
 endif()