simplify what was ported from the makefiles

* remove some of the complicated logic.
  The additional warnings always make sense.
  CMake uses the state of `BUILD_SHARED_LIBS` to determine the library
  target type.
  Also remove the comment regarding building shared and static at the
  same time, as usually that's done as necessary by the user.
* append user-defined {C,LD}FLAGS instead of preprending - we expect
  them to know what they do, so they can override our defaults
* use target_{compile,link}_options() instead of setting variables

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

Author: sjaeckel

CMakeLists.txt

@@ -20,49 +20,38 @@ option(BUILD_SHARED_LIBS "Build shared library and only the shared library if \"
 # Compose CFLAGS
 #-----------------------------------------------------------------------------
 
-# check if there was one already set.
-if(DEFINED ENV{LTM_CFLAGS})
-   set(LTM_C_FLAGS  $ENV{LTM_CFLAGS})
-endif()
-if(DEFINED ENV{LTM_LDFLAGS})
-   set(LTM_LD_FLAGS  $ENV{LTM_LDFLAGS})
-endif()
-
 # Some information copied from makefile_include.mk
 
 # Basic set
-set(LTM_C_FLAGS  "${LTM_C_FLAGS}  -Wall -Wsign-compare -Wextra -Wshadow")
+set(LTM_C_FLAGS  -Wall -Wsign-compare -Wextra -Wshadow)
+set(LTM_C_FLAGS  ${LTM_C_FLAGS} -Wdeclaration-after-statement -Wbad-function-cast -Wcast-align)
+set(LTM_C_FLAGS  ${LTM_C_FLAGS} -Wstrict-prototypes -Wpointer-arith)
 
 # Do we run the sanitizer?
 if(DEFINED ENV{SANITIZER})
-    set(LTM_C_FLAGS  "${LTM_C_FLAGS} -fsanitize=undefined -fno-sanitize-recover=all -fno-sanitize=float-divide-by-zero")
-endif()
-
-if(NOT DEFINED ENV{NO_ADDTL_WARNINGS})
-    set(LTM_C_FLAGS  "${LTM_C_FLAGS} -Wdeclaration-after-statement -Wbad-function-cast -Wcast-align")
-    set(LTM_C_FLAGS  "${LTM_C_FLAGS} -Wstrict-prototypes -Wpointer-arith")
+    set(LTM_C_FLAGS  ${LTM_C_FLAGS} -fsanitize=undefined -fno-sanitize-recover=all -fno-sanitize=float-divide-by-zero)
 endif()
 
 if(DEFINED ENV{CONV_WARNINGS})
-    set(LTM_C_FLAGS  "${LTM_C_FLAGS} -std=c89 -Wconversion -Wsign-conversion")
+    set(LTM_C_FLAGS  ${LTM_C_FLAGS} -std=c89 -Wconversion -Wsign-conversion)
     if($ENV{CONV_WARNINGS} EQUAL "strict")
-        set(LTM_C_FLAGS  "${LTM_C_FLAGS} -Wc++-compat")
+        set(LTM_C_FLAGS  ${LTM_C_FLAGS} -Wc++-compat)
     endif()
 else()
-    set(LTM_C_FLAGS  "${LTM_C_FLAGS} -Wsystem-headers")
+    set(LTM_C_FLAGS  ${LTM_C_FLAGS} -Wsystem-headers)
 endif()
 
 if(DEFINED ENV{COMPILE_DEBUG})
-    set(LTM_C_FLAGS  "${LTM_C_FLAGS} -g3")
+    set(LTM_C_FLAGS  ${LTM_C_FLAGS} -g3)
 endif()
 
 if(DEFINED ENV{COMPILE_SIZE})
-    set(LTM_C_FLAGS  "${LTM_C_FLAGS} -Os")
+    set(LTM_C_FLAGS  ${LTM_C_FLAGS} -Os)
 else()
     if(NOT DEFINED ENV{IGNORE_SPEED})
-        set(LTM_C_FLAGS  "${LTM_C_FLAGS} -O3 -funroll-loops")
+        set(LTM_C_FLAGS  ${LTM_C_FLAGS} -O3 -funroll-loops)
         #x86 optimizations [should be valid for any GCC install though]
-        set(LTM_C_FLAGS  "${LTM_C_FLAGS} -fomit-frame-pointer")
+        set(LTM_C_FLAGS  ${LTM_C_FLAGS} -fomit-frame-pointer)
     endif()
     # TODO:
     # if(DEFINED ENV{COMPILE_LTO})
@@ -72,70 +61,56 @@ else()
     # endif()
 endif()
 
+# TODO
+# Are the coming three checks really the best way?
+
 # What compiler do we have and what are their...uhm... peculiarities
 # TODO: is the check for a C++ compiler necessary?
 if( (CMAKE_C_COMPILER_ID MATCHES "(C|c?)lang") OR (CMAKE_CXX_COMPILER_ID MATCHES "(C|c?)lang"))
-    set(LTM_C_FLAGS  "${LTM_C_FLAGS} -Wno-typedef-redefinition -Wno-tautological-compare -Wno-builtin-requires-header")
+    set(LTM_C_FLAGS  ${LTM_C_FLAGS} -Wno-typedef-redefinition -Wno-tautological-compare -Wno-builtin-requires-header)
 endif()
 
 if( (CMAKE_C_COMPILER_ID MATCHES "mingw") OR (CMAKE_CXX_COMPILER_ID MATCHES "mingw"))
-    set(LTM_C_FLAGS  "${LTM_C_FLAGS}  -Wno-shadow")
+    set(LTM_C_FLAGS  ${LTM_C_FLAGS}  -Wno-shadow)
 endif()
 
 if(DEFINED ENV{PLATFORM})
     if($ENV{PLATFORM} MATCHES "Darwin")
-        set(LTM_C_FLAGS  "${LTM_C_FLAGS}  -Wno-nullability-completeness")
+        set(LTM_C_FLAGS  ${LTM_C_FLAGS}  -Wno-nullability-completeness)
     endif()
     if($ENV{PLATFORM} MATCHES "CYGWIN")
-        set(LTM_C_FLAGS  "${LTM_C_FLAGS} -no-undefined")
+        set(LTM_C_FLAGS  ${LTM_C_FLAGS} -no-undefined)
     endif()
 endif()
 
 # TODO: coverage (lgcov)
 
-# We have several private functions in the library and the "demo/test" programm
-# needs a littkle note to be able to switch them off. Please use the static build
-# to get a full test.
-if(BUILD_SHARED_LIBS)
-    set(LTM_C_FLAGS  "${LTM_C_FLAGS} -DLTM_TEST_DYNAMIC")
+# If the user set the environment variables at generate-time, append them
+# in order to allow overriding our defaults.
+if(DEFINED ENV{LTM_CFLAGS})
+   set(LTM_C_FLAGS  ${LTM_C_FLAGS} $ENV{LTM_CFLAGS})
+endif()
+if(DEFINED ENV{LTM_LDFLAGS})
+   set(LTM_LD_FLAGS  ${LTM_LD_FLAGS} $ENV{LTM_LDFLAGS})
 endif()
-
-# Bring it home
-set(CMAKE_C_FLAGS         "${LTM_C_FLAGS}")
-set(CMAKE_C_FLAGS_DEBUG   "${LTM_C_FLAGS}")
-set(CMAKE_C_FLAGS_RELEASE "${LTM_C_FLAGS}")
 
 #-----------------------------------------------------------------------------
 # library target
 #-----------------------------------------------------------------------------
-
-# TODO: There may be a way but I found none to build both at once without complication.
-#       It is possible with e.g. Linux where the static library is named libtommath.a
-#       and the dynamic library libtommath.so*, two different names.
-#       That is not the case with e.g. Windows where both types have the same name.
-#       See also:
-#       https://stackoverflow.com/questions/2152077/is-it-possible-to-get-cmake-to-build-both-a-static-and-shared-library-at-the-sam
-if(BUILD_SHARED_LIBS)
-    add_library(${PROJECT_NAME} SHARED
-        ${SOURCES}
-    )
-else()
-    add_library(${PROJECT_NAME} STATIC
-        ${SOURCES}
-    )
-endif()
-
-# Clear cache manually
-unset(BUILD_SHARED_LIBS CACHE)
+add_library(${PROJECT_NAME}
+    ${SOURCES}
+)
 
 target_include_directories(${PROJECT_NAME} PUBLIC
     $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
     $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/${PROJECT_NAME}>
 )
 
-target_include_directories(${PROJECT_NAME} PUBLIC
-    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
-    $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/${PROJECT_NAME}>
+target_compile_options(${PROJECT_NAME} BEFORE PRIVATE
+    ${LTM_C_FLAGS}
+)
+target_link_options(${PROJECT_NAME} BEFORE PRIVATE
+    ${LTM_LD_FLAGS}
 )
 
 set_target_properties(${PROJECT_NAME} PROPERTIES VERSION ${PROJECT_VERSION})
@@ -159,17 +134,13 @@ target_link_libraries(test-target PRIVATE
     ${PROJECT_NAME}
 )
 
-# for the SHARED_LIBRARY build we need some special flags enabled
-# We also allow our users to override our selection by defining their own
-# `CMAKE_C_FLAGS` on generation-phase. CMake itself doesn't allow a user
-# to override settings defined in the CMakeLists.txt so we append it manually
-# again even though CMake prepended it already.
 target_compile_options(test-target BEFORE PRIVATE
     $<$<STREQUAL:$<TARGET_PROPERTY:${PROJECT_NAME},TYPE>,SHARED_LIBRARY>:-O1 -DLTM_TEST_DYNAMIC>
-    ${CMAKE_C_FLAGS}
+    ${LTM_C_FLAGS}
 )
 target_link_options(test-target BEFORE PRIVATE
     $<$<STREQUAL:$<TARGET_PROPERTY:${PROJECT_NAME},TYPE>,SHARED_LIBRARY>:-O1>
+    ${LTM_LD_FLAGS}
 )
 
 #-----------------------------------------------------------------------------
@@ -191,6 +162,7 @@ set(TARGETS_EXPORT_NAME "${PROJECT_NAME}Targets")
 
 install(TARGETS ${PROJECT_NAME}
     EXPORT ${TARGETS_EXPORT_NAME}
+    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
     ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
 )