mirror of
https://github.com/ttroy50/cmake-examples.git
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add compile flags example
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ttroy50
@@ -10,7 +10,7 @@ toc::[]
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Introduction
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------------
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CMake has a number of build in build configurations which can be used to compile
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CMake has a number of built in build configurations which can be used to compile
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your project. These specify the optimization levels and if debug information is
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to be included in the binary.
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@@ -21,9 +21,6 @@ The levels provided are:
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* MinSizeRel - Adds `-Os -DNDEBUG`
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* RelWithDebInfo - Adds `-O2 -g -DNDEBUG` flags
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Shows a hello world example which first creates and links a static library
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The files in this tutorial are below:
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```
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@@ -78,9 +75,6 @@ if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
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endif()
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----
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When creating an executable that will use your library you must tell the compiler
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about the library. This can be done using the +target_link_library()+ function.
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[[building-the-example]]
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Building the Example
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~~~~~~~~~~~~~~~~~~~~
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10
01-basic/G-compile-flags/CMakeLists.txt
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10
01-basic/G-compile-flags/CMakeLists.txt
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@@ -0,0 +1,10 @@
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cmake_minimum_required(VERSION 2.6)
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# Set a default C++ compile flag
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set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DEX2" CACHE STRING "Set C++ Compiler Flags" FORCE)
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# Set the project name
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project (compile_flags)
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# Add an executable
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add_executable(cmake_examples_compile_flags main.cpp)
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122
01-basic/G-compile-flags/README.adoc
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122
01-basic/G-compile-flags/README.adoc
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@@ -0,0 +1,122 @@
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= Compile Flags
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:toc:
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:toc-placement!:
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toc::[]
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[[intro]]
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Introduction
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------------
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CMake supports setting compile flags using the +CMAKE_C_FLAGS+ and +CMAKE_CXX_FLAGS+
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variables. Similarly linker flags can be set using the +CMAKE_LINKER_FLAGS+.
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The files in this tutorial are below:
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```
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$ tree
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.
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├── CMakeLists.txt
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├── main.cpp
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```
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* CMakeLists.txt - Contains the CMake commands you wish to run
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* main.cpp - The source file with main
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[[concepts]]
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Concepts
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~~~~~~~~
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[[set-cpp-flag]]
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Set C++ Flag
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^^^^^^^^^^^^
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Similar to the build type a C++ compiler flag can be set using the following methods.
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- Using a gui tool such as ccmake / cmake-gui
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image::cmake-gui-set-cxx-flag.png[cmake-gui set cxx flag]
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- Passing into cmake
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[source,cmake]
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----
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cmake .. -DCMAKE_CXX_FLAGS="-DEX3"
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----
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[[set-default-flag]]
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Set Default C++ Flags
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^^^^^^^^^^^^^^^^^^^^^
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The default `CMAKE_CXX_FLAGS` is either empty or contains the appropriate flags
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for the build type.
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To set additional default compile flags you can add the following to your
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top level CMakeLists.txt
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[source,cmake]
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----
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set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DEX2" CACHE STRING "Set C++ Compiler Flags" FORCE)
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----
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[NOTE]
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====
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The values `CACHE STRING "Set C++ Compiler Flags" FORCE` from the above command
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are used to force this variable to be set in the CMakeCache.txt file.
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For more details, see https://cmake.org/cmake/help/v3.0/command/set.html[here]
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====
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[[building-the-example]]
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Building the Example
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~~~~~~~~~~~~~~~~~~~~
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[source,bash]
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----
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$ mkdir build
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$ cd build/
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$ cmake ..
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-- The C compiler identification is GNU 4.8.4
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-- The CXX compiler identification is GNU 4.8.4
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-- Check for working C compiler: /usr/bin/cc
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-- Check for working C compiler: /usr/bin/cc -- works
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-- Detecting C compiler ABI info
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-- Detecting C compiler ABI info - done
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-- Check for working CXX compiler: /usr/bin/c++
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-- Check for working CXX compiler: /usr/bin/c++ -- works
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-- Detecting CXX compiler ABI info
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-- Detecting CXX compiler ABI info - done
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-- Configuring done
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-- Generating done
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-- Build files have been written to: /home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build
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$ make VERBOSE=1
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/usr/bin/cmake -H/home/matrim/workspace/cmake-examples/01-basic/G-compile-flags -B/home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build --check-build-system CMakeFiles/Makefile.cmake 0
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/usr/bin/cmake -E cmake_progress_start /home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build/CMakeFiles /home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build/CMakeFiles/progress.marks
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make -f CMakeFiles/Makefile2 all
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make[1]: Entering directory `/home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build'
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make -f CMakeFiles/cmake_examples_compile_flags.dir/build.make CMakeFiles/cmake_examples_compile_flags.dir/depend
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make[2]: Entering directory `/home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build'
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cd /home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build && /usr/bin/cmake -E cmake_depends "Unix Makefiles" /home/matrim/workspace/cmake-examples/01-basic/G-compile-flags /home/matrim/workspace/cmake-examples/01-basic/G-compile-flags /home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build /home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build /home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build/CMakeFiles/cmake_examples_compile_flags.dir/DependInfo.cmake --color=
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Dependee "/home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build/CMakeFiles/cmake_examples_compile_flags.dir/DependInfo.cmake" is newer than depender "/home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build/CMakeFiles/cmake_examples_compile_flags.dir/depend.internal".
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Dependee "/home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build/CMakeFiles/CMakeDirectoryInformation.cmake" is newer than depender "/home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build/CMakeFiles/cmake_examples_compile_flags.dir/depend.internal".
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Scanning dependencies of target cmake_examples_compile_flags
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make[2]: Leaving directory `/home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build'
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make -f CMakeFiles/cmake_examples_compile_flags.dir/build.make CMakeFiles/cmake_examples_compile_flags.dir/build
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make[2]: Entering directory `/home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build'
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/usr/bin/cmake -E cmake_progress_report /home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build/CMakeFiles 1
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[100%] Building CXX object CMakeFiles/cmake_examples_compile_flags.dir/main.cpp.o
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/usr/bin/c++ -DEX2 -o CMakeFiles/cmake_examples_compile_flags.dir/main.cpp.o -c /home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/main.cpp
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Linking CXX executable cmake_examples_compile_flags
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/usr/bin/cmake -E cmake_link_script CMakeFiles/cmake_examples_compile_flags.dir/link.txt --verbose=1
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/usr/bin/c++ -DEX2 CMakeFiles/cmake_examples_compile_flags.dir/main.cpp.o -o cmake_examples_compile_flags -rdynamic
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make[2]: Leaving directory `/home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build'
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/usr/bin/cmake -E cmake_progress_report /home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build/CMakeFiles 1
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[100%] Built target cmake_examples_compile_flags
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make[1]: Leaving directory `/home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build'
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/usr/bin/cmake -E cmake_progress_start /home/matrim/workspace/cmake-examples/01-basic/G-compile-flags/build/CMakeFiles 0
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----
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17
01-basic/G-compile-flags/main.cpp
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17
01-basic/G-compile-flags/main.cpp
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@@ -0,0 +1,17 @@
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#include <iostream>
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int main(int argc, char *argv[])
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{
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std::cout << "Hello Compile Flags!" << std::endl;
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// only print if compile flag set
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#ifdef EX2
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std::cout << "Hello Compile Flag EX2!" << std::endl;
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#endif
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#ifdef EX3
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std::cout << "Hello Compile Flag EX3!" << std::endl;
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#endif
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return 0;
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}
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@@ -1,6 +1,9 @@
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# Basic Examples
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= Basic Examples
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The basic examples in this directory show how the setup a cmake project and create an executable. The examples included are
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The basic examples in this directory show how the setup a CMake project,
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set compile flags, create executables and libraries, and install them.
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create an executable. The examples included are
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- hello-cmake. A hello world example.
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- hello-headers. A slighly more complicated hello world example, with using Hello class and seperate source and include folders.
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@@ -8,3 +11,4 @@ The basic examples in this directory show how the setup a cmake project and crea
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- static-library. An example using a static library.
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- installing. Shows how to create a 'make install' target to install the binaries and libraries
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- build-type. An example showing how to set a default build type of your project.
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- compile-flags. Shows how to set compile flags
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