Useful cmake macros that help with: compiler/linker flags, collecting sources, PCHs, Unity builds and other stuff.

ucm - useful cmake macros

ucm is a collection of cmake macros that help with:

• managing compiler/linker flags
• collecting source files with grouping in IDEs that mimics the filesystem structure
• easy removing source files from already collected ones
• adding a precompiled header for targets
• unity builds of targets
• others... contribution is welcome!

Tested with MSVC/GCC/Clang.

cotire is an optional submodule for the ucm_add_target() macro either do git submodule update --init after cloning or include cotire in your cmake files before ucm.

Documentation

Macros:

• ucm_print_flags
• ucm_add_flags
• ucm_set_flags
• ucm_add_linker_flags
• ucm_set_linker_flags
• ucm_set_runtime
• ucm_set_xcode_attrib
• ucm_add_files
• ucm_add_dirs
• ucm_count_sources
• ucm_include_file_in_sources
• ucm_dir_list
• ucm_remove_files
• ucm_remove_directories
• ucm_add_target

Macro notation: myMacro(NAME <name> [FLAG]) - NAME and a name after it are required and FLAG is optional (because in brackets).

macro ucm_print_flags()

Prints all relevant flags - for example with -DCMAKE_BUILD_TYPE=Debug given to cmake for makefiles:

CMAKE_C_FLAGS_DEBUG: -g
CMAKE_CXX_FLAGS_DEBUG: -g
CMAKE_C_FLAGS:  --save-temps -std=c++98 -pedantic -m64 -O2 -fvisibility=hidden
CMAKE_CXX_FLAGS:  --save-temps -std=c++98 -pedantic -m64 -O2 -fvisibility=hidden

or for a multi config generator like Visual Studio:

CMAKE_C_FLAGS_DEBUG: /D_DEBUG /MDd /Zi /Ob0 /Od /RTC1
CMAKE_CXX_FLAGS_DEBUG: /D_DEBUG /MDd /Zi /Ob0 /Od /RTC1
CMAKE_C_FLAGS_RELEASE: /MD /O2 /Ob2 /D NDEBUG
CMAKE_CXX_FLAGS_RELEASE: /MD /O2 /Ob2 /D NDEBUG
CMAKE_C_FLAGS:  /DWIN32 /D_WINDOWS /W3 /W4
CMAKE_CXX_FLAGS:  /DWIN32 /D_WINDOWS /W3 /GR /EHsc /W4

macro ucm_add_flags([C] [CXX] [CONFIG <config>] flag1 flag2 flag3...)

Append the flags to a different set depending on it's options - examples:

ucm_add_flags(-O3 -Wextra) # will add to CMAKE_C_FLAGS and CMAKE_CXX_FLAGS
ucm_add_flags(C -O3) # will add to CMAKE_C_FLAGS
ucm_add_flags(CXX -O3) # will add to CMAKE_CXX_FLAGS
ucm_add_flags(-O3 -Wall CONFIG Debug) # will add to CMAKE_C_FLAGS_DEBUG and CMAKE_CXX_FLAGS_DEBUG
ucm_add_flags(C -Wall CONFIG Debug Release) # will add to CMAKE_C_FLAGS_DEBUG and CMAKE_C_FLAGS_RELEASE

macro ucm_set_flags([C] [CXX] [CONFIG <config>] flag1 flag2 flag3...)

Removes the old and sets the new flags to a different set depending on it's options - examples:

ucm_set_flags(CXX) # will clear CMAKE_CXX_FLAGS
ucm_set_flags() # will clear both CMAKE_C_FLAGS and CMAKE_CXX_FLAGS
ucm_set_flags(CXX -O3) # will set CMAKE_CXX_FLAGS
ucm_set_flags(-O3 -Wall CONFIG Debug) # will set CMAKE_C_FLAGS_DEBUG and CMAKE_CXX_FLAGS_DEBUG

macro ucm_add_linker_flags([EXE] [MODULE] [SHARED] [STATIC] [CONFIG <config>] flag1 flag2 flag3...)

Append the flags to a different set depending on it's options - examples:

ucm_add_linker_flags(/NXCOMPAT) # will add to CMAKE_<TYPE>_LINKER_FLAGS (TYPE is all 4 - exe/module/shared/static)
ucm_add_linker_flags(EXE /DYNAMICBASE CONFIG Release) # will add to CMAKE_EXE_LINKER_FLAGS_RELEASE only
ucm_add_flags(EXE /DYNAMICBASE CONFIG Debug Release) # will add to CMAKE_EXE_LINKER_FLAGS_DEBUG and CMAKE_EXE_LINKER_FLAGS_RELEASE

macro ucm_set_linker_flags([EXE] [MODULE] [SHARED] [STATIC] [CONFIG <config>] flag1 flag2 flag3...)

Removes the old and sets the new flags to a different set depending on it's options - examples:

ucm_set_linker_flags(/NXCOMPAT) # will clear all CMAKE_<TYPE>_LINKER_FLAGS
ucm_set_linker_flags(EXE /DYNAMICBASE CONFIG Release) # will set CMAKE_EXE_LINKER_FLAGS_RELEASE only

macro ucm_set_runtime([STATIC] [DYNAMIC])

Sets the runtime to static/dynamic - for example with Visual Studio as a generator:

ucm_print_flags()
ucm_set_runtime(STATIC)
ucm_print_flags()

will result in:

CMAKE_C_FLAGS_DEBUG: /D_DEBUG /MDd /Zi /Ob0 /Od /RTC1
CMAKE_CXX_FLAGS_DEBUG: /D_DEBUG /MDd /Zi /Ob0 /Od /RTC1
CMAKE_C_FLAGS_RELEASE: /MD /O2 /Ob2 /D NDEBUG
CMAKE_CXX_FLAGS_RELEASE: /MD /O2 /Ob2 /D NDEBUG
CMAKE_C_FLAGS:  /DWIN32 /D_WINDOWS /W3 /W4
CMAKE_CXX_FLAGS:  /DWIN32 /D_WINDOWS /W3 /GR /EHsc /W4

CMAKE_C_FLAGS_DEBUG: /D_DEBUG /MTd /Zi /Ob0 /Od /RTC1
CMAKE_CXX_FLAGS_DEBUG: /D_DEBUG /MTd /Zi /Ob0 /Od /RTC1
CMAKE_C_FLAGS_RELEASE: /MT /O2 /Ob2 /D NDEBUG
CMAKE_CXX_FLAGS_RELEASE: /MT /O2 /Ob2 /D NDEBUG
CMAKE_C_FLAGS:  /DWIN32 /D_WINDOWS /W3 /W4
CMAKE_CXX_FLAGS:  /DWIN32 /D_WINDOWS /W3 /GR /EHsc /W4

macro ucm_set_xcode_attrib(name value [CLEAR] [CONFIG <config>])

Sets an Xcode attribute and optionally per-configuration:

ucm_set_xcode_attrib(DEBUG_INFORMATION_FORMAT "dwarf-with-dsym")
ucm_set_xcode_attrib(DEAD_CODE_STRIPPING "YES" CONFIG Debug Release)

will result in:

CMAKE_XCODE_ATTRIBUTE_DEBUG_INFORMATION_FORMAT: "dwarf-with-dsym"
CMAKE_XCODE_ATTRIBUTE_DEAD_CODE_STRIPPING[variant=Debug]: "YES"
CMAKE_XCODE_ATTRIBUTE_DEAD_CODE_STRIPPING[variant=Release]: "YES"

macro ucm_add_files(src1 src2 scr3... TO <sources> [FILTER_POP <num>])

Adds the sources to the sources variable and sets up filters for the solution explorer of Visual Studio (probably for XCode/CodeBlocks too).

The filters will mimic the filesystem - if we have given dir1/test/a.cpp we would have by default dir1/test as nested filters in the solution explorer. This can be controlled with FILTER_POP - 1 would result in only test as a filter and 2 would result in no filter for a.cpp - see ucm_add_dirs for a visual example.

ucm_add_files("dir/some1.cpp" "dir/some1.h" TO sources)

macro ucm_add_dirs(dir1 dir2 dir3... TO <sources> [RECURSIVE] [FILTER_POP <num>] [ADDITIONAL_EXT ext1 ext2 ...])

Adds all sources (sources and headers with all valid c/c++ extensions) from the directories given.

Can be recursive with the RECURSIVE flag.

Like ucm_add_files() filters for the solution explorer of IDEs can be controlled with FILTER_POP - example:

CMake code	result
ucm_add_dirs(util TO sources)
ucm_add_dirs(util TO sources FILTER_POP 1)

Additional extensions for collection can be added with the ADDITIONAL_EXT list.

macro ucm_count_sources(src1 src2 src3... RESULT <result>)

Given a list of sources - returns the number of source files (no headers - only valid source extensions) in the result.

set(sources "a.cpp;b.cpp;h.hpp")
ucm_count_sources(${sources} c.cpp d.cpp RESULT res) # would return 4 in res

macro ucm_include_file_in_sources(src1 src2 src3... HEADER <header>)

Includes the header in the source file with a compile flag (without modifying the file) either with -include "hdr.h" or with /FI"hdr.h" depending on the compiler.

ucm_include_file_in_sources(c.cc a.cc b.cc HEADER "common.h")

macro ucm_dir_list(<thedir> <result>)

Returns a list of subdirectories for a given directory.

ucm_dir_list("the/dir" result)

macro ucm_remove_files(src1 src2 src3... FROM <sources>)

Removes the given source files from the sources list - example:

ucm_add_dirs(utils REC TO sources)
ucm_remove_files(utils/deprecated.h FROM sources)

macro ucm_remove_directories(dir1 dir2 dir3... FROM <sources> [MATCHES pttrn1 pttrn2])

Removes all source files from the given directories from the sources list (recursively) - example:

ucm_add_dirs(utils REC TO sources)
# and then remove only the ones we don't want
ucm_remove_directories(utils/deprecated utils/experimental FROM sources)

Patterns can also be given like this:

ucm_remove_directories(utils FROM sources MATCHES win32)

macro ucm_add_target(NAME <name> TYPE <EXECUTABLE|STATIC|SHARED|MODULE> SOURCES src1 src2 src3... [PCH_FILE <pch>] [UNITY [CPP_PER_UNITY <num>] [UNITY_EXCLUDED excl_src1 excl_src2 ...]])

A wrapper of add_library() and add_executable() calls. Uses cotire for platform/compiler independent usage of precompiled headers and/or making a unity build of the target.

For information about unity builds in general go to the bottom.

ucm_add_target(NAME example TYPE EXECUTABLE SOURCES "${sources}" PCH_FILE precompiled.h)

The example above shows how to add a target with a precompiled header.

ucm_add_target(NAME example TYPE EXECUTABLE SOURCES "${sources}" UNITY CPP_PER_UNITY 20 UNITY_EXCLUDED "separate/some2.cpp")

When the UCM_UNITY_BUILD ucm option is set to ON (OFF by default) a target registered like in the example above will actually result in 2 targets added - the unity target with example as a name (included in the build by default) and the original target with example_ORIGINAL as a name (excluded from the build by default). This allows the user to browse and modify the sources in the original target properly within the IDE. Also separate/some2.cpp will be built normally and will not be included in the unity sources.

When new sources are added to the original target the unity target will be updated accordingly by cotire.

The order in which sources are given to SOURCES is the order in which they will appear in the unity files so you can combat compilation issues by changing the order of the source files.

Targets can be excluded from unity builds by adding them in the UCM_UNITY_BUILD_EXCLUDE_TARGETS list when invoking cmake (handy if a target becomes problematic in a unity build or if you want to iterate fast on a particular target and want to compile it's sources separately).

Mixed language targets (C/C++) are handled properly - separate unity files are generated for the different languages.

The macro will self-diagnose the target and if it has more than 1 source file and has not been registered with the UNITY flag a developer warning will be printed that the target may benefit from a unity build.

CPP_PER_UNITY - to explicitly say how many source files should go into a unity source (default is 100). Another option is to pass not a number but -jX after CPP_PER_UNITY and that would mean dividing the sources into X unity sources.

UNITY_EXCLUDED - list of files from the target that should be excluded from unify-ing (will be used normally by themselves - can be used to fix compilation errors).

Unity examples - given 100 .cpp files in the target:

• CPP_PER_UNITY 5 would mean 20 .cxx unity files including 5 of the original .cpp files each
• CPP_PER_UNITY 10 would mean 10 .cxx unity files including 10 of the original .cpp files each
• CPP_PER_UNITY -j8 would mean 8 .cxx unity files dividing the original 100 among them

How a unity target looks in the IDE:

Unity builds

For all the pros and cons checkout my blog post.