How do I add a linker or compile flag in a CMake file

Question

I am using the arm-linux-androideabi-g   compiler  When I try to compile a simple  Hello  World   program it compiles fine  When I test it by adding a simple exception handling in that code it works too  after adding -fexceptions    I guess it is disabled by default    This is for an Android device  and I only want to use CMake  not ndk-build   For example - first cpp   include  lt iostream gt   using namespace std   int main        try              catch                    return 0        arm-linux-androideadi-g   -o first-test first cpp -fexceptions  It works with no problem     The problem     I am trying to compile the file with a CMake file   I want to add the -fexceptions as a flag  I tried with  set  CMAKE EXE LINKER FLAGS -fexceptions   or set  CMAKE EXE LINKER FLAGS  fexceptions      and  set   CMAKE C FLAGS  fexceptions     It still displays an error

User · Answer

Try setting the variable CMAKE CXX FLAGS instead of CMAKE C FLAGS   set  CMAKE CXX FLAGS  -fexceptions     The variable CMAKE C FLAGS only affects the C compiler  but you are compiling C   code    Adding the flag to CMAKE EXE LINKER FLAGS is redundant

User · Answer

Suppose you want to add those flags  better to declare them in a constant    SET GCC COVERAGE COMPILE FLAGS  -fprofile-arcs -ftest-coverage   SET GCC COVERAGE LINK FLAGS     -lgcov     There are several ways to add them    The easiest one  not clean  but easy and convenient  and works only for compile flags  C  amp  C   at once    add definitions   GCC COVERAGE COMPILE FLAGS    Appending to corresponding CMake variables   SET CMAKE CXX FLAGS     CMAKE CXX FLAGS    GCC COVERAGE COMPILE FLAGS    SET CMAKE EXE LINKER FLAGS     CMAKE EXE LINKER FLAGS    GCC COVERAGE LINK FLAGS     Using target properties  cf  doc CMake compile flag target property and need to know the target name   get target property TEMP   THE TARGET  COMPILE FLAGS  if TEMP STREQUAL  TEMP-NOTFOUND     SET TEMP       Set to empty string else     SET TEMP    TEMP       A space to cleanly separate from existing content endif     Append our values SET TEMP    TEMP   GCC COVERAGE COMPILE FLAGS     set target properties   THE TARGET  PROPERTIES COMPILE FLAGS   TEMP       Right now I use method 2

User · Answer

The preferred way to specify toolchain-specific options is using CMake s toolchain facility  This ensures that there is a clean division between   instructions on how to organise source files into targets -- expressed in CMakeLists txt files  entirely toolchain-agnostic  and details of how certain toolchains should be configured -- separated into CMake script files  extensible by future users of your project  scalable   Ideally  there should be no compiler linker flags in your CMakeLists txt files -- even within if endif blocks  And your program should build for the native platform with the default toolchain  e g  GCC on GNU Linux or MSVC on Windows  without any additional flags  Steps to add a toolchain   Create a file  e g  arm-linux-androideadi-gcc cmake with global toolchain settings  set CMAKE CXX COMPILER arm-linux-gnueabihf-g    set CMAKE CXX FLAGS INIT  quot -fexceptions quot     You can find an example Linux cross-compiling toolchain file here    When you want to generate a build system with this toolchain  specify the CMAKE TOOLCHAIN FILE parameter on the command line  mkdir android-arm-build  amp  amp  cd android-arm-build cmake -DCMAKE TOOLCHAIN FILE   pwd     arm-linux-androideadi-gcc cmake      Note  you cannot use a relative path    Build as normal  cmake --build      Toolchain files make cross-compilation easier  but they have other uses   Hardened diagnostics for your unit tests  set CMAKE CXX FLAGS INIT  quot -Werror -Wall -Wextra -Wpedantic quot     Tricky-to-configure development tools    toolchain file for use with gcov set CMAKE CXX FLAGS INIT  quot --coverage -fno-exceptions -g quot     Enhanced safety checks    toolchain file for use with gdb set CMAKE CXX FLAGS DEBUG INIT  quot -fsanitize address undefined -fsanitize-undefined-trap-on-error quot   set CMAKE EXE LINKER FLAGS INIT  quot -fsanitize address undefined -static-libasan quot

User · Answer

You can also add linker flags to a specific target using the LINK FLAGS property   set property TARGET   target  APPEND STRING PROPERTY LINK FLAGS     flag      If you want to propagate this change to other targets  you can create a dummy target to link to

User · Answer

In newer versions of CMake you can set compiler and linker flags for a single target with target compile options and target link libraries respectively  yes  the latter sets linker options too    target compile options first-test PRIVATE -fexceptions    The advantage of this method is that you can control propagation of options to other targets that depend on this one via PUBLIC and PRIVATE   As of CMake 3 13 you can also use target link options to add linker options which makes the intent more clear

[c++] How do I add a linker or compile flag in a CMake file?

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