Build systems

How to create conan debug profile

Run this command to create a debug profile from your default profile:

cp ~/.conan/profiles/default ~/.conan/profiles/debug && sed -i -e 's/Release/Debug/g' ~/.conan/profiles/debug

Example output from conan profile show debug:

[settings]
os=Linux
os_build=Linux
arch=x86_64
arch_build=x86_64
compiler=gcc
compiler.version=9
compiler.libcxx=libstdc++
build_type=Debug
[options]
[conf]
[build_requires]
[env]

 

Posted by Uli Köhler in C/C++, Conan

How to list local conan packages

In order to list local conan packages, run

conan search

Example output:

$ conan search
Existing package recipes:

cpr/1.6.2
elasticlient/0.2
elasticlient/[email protected]/testing
gtest/cci.20210126
jsoncpp/1.9.4
libcurl/7.69.1
libcurl/7.78.0
openssl/1.1.1l
zlib/1.2.11

 

Posted by Uli Köhler in Conan

How to fix Conan CMake “Could NOT find OpenSSL”

Problem:

When building your conan package, you see this CMake error:

CMake Error at /usr/share/cmake-3.16/Modules/FindPackageHandleStandardArgs.cmake:146 (message):
  Could NOT find OpenSSL, try to set the path to OpenSSL root folder in the
  system variable OPENSSL_ROOT_DIR (missing: OPENSSL_CRYPTO_LIBRARY
  OPENSSL_INCLUDE_DIR)
Call Stack (most recent call first):
  /usr/share/cmake-3.16/Modules/FindPackageHandleStandardArgs.cmake:393 (_FPHSA_FAILURE_MESSAGE)
  /usr/share/cmake-3.16/Modules/FindOpenSSL.cmake:447 (find_package_handle_standard_args)
  ../_deps/curl-src/CMakeLists.txt:365 (find_package)

even though your conanfile.py declares OpenSSL as a dependency:

class MyPackageConan(ConanFile):
    # ...
    requires = ("openssl/1.1.1l", )

Solution:

Make sure that the project’s CMakeLists.txt contains these lines:

include(${CMAKE_BINARY_DIR}/conanbuildinfo.cmake)
conan_basic_setup()

Typically, the way to do this is to use this code which is automatically generated by conan new:

        # This small hack might be useful to guarantee proper /MT /MD linkage
        # in MSVC if the packaged project doesn't have variables to set it
        # properly
        tools.replace_in_file("hello/CMakeLists.txt", "PROJECT(HelloWorld)",
                              '''PROJECT(HelloWorld)
include(${CMAKE_BINARY_DIR}/conanbuildinfo.cmake)
conan_basic_setup()''')

in source() like this:

    def source(self):
        self.run("git clone https://github.com/conan-io/hello.git")
        # This small hack might be useful to guarantee proper /MT /MD linkage
        # in MSVC if the packaged project doesn't have variables to set it
        # properly
        tools.replace_in_file("hello/CMakeLists.txt", "PROJECT(HelloWorld)",
                              '''PROJECT(HelloWorld)
include(${CMAKE_BINARY_DIR}/conanbuildinfo.cmake)
conan_basic_setup()''')

Note that you need to replace both hello/CMakeLists.txt with the correct filename (typically, just replace hello by). Also, you need to replace both instances PROJECT(HelloWorld) by the actual line from your CMakeLists.txt in order for the replace command to work.

Posted by Uli Köhler in C/C++, CMake, Conan

How to add build-only dependencies in Conan recipe

Just add build_requires = ('dep1/version1', 'dep1/version2') to your conanfile.py:

class MyPackageConan(ConanFile):
    # ...
    requires = ("openssl/1.1.1l", )
    build_requires = ("jsoncpp/1.9.4", )

 

Posted by Uli Köhler in C/C++, Conan

How to run ‘git submodule update’ in Conan recipe

If you want to run git submodule update in your conanfile.py, you can simple add a self.run() command after the git clone command:

self.run("git clone https://github.com/conan-io/hello.git")
self.run("cd hello && git submodule update --init --recursive")

Full example:

self.run("git clone https://github.com/seznam/elasticlient.git -b version-0.2")
self.run("cd elasticlient && git submodule update --init --recursive")

Note that you need to cd <directory> && git submodule update

Posted by Uli Köhler in C/C++, Conan

How to add conan CMake build definition

When building a library using conan, this is the default conanfile.py definition for building using CMake

cmake = CMake(self)
cmake.configure(source_folder="hello")
cmake.build()

You can easily add definitions like this:

cmake.definitions["MY_FLAG"] = "1"

This will generate -DMY_FLAG=1 when calling CMake

Full example:

cmake = CMake(self)
cmake.definitions["USE_SYSTEM_CPR"] = "1
cmake.configure(source_folder="elasticlient")"
cmake.build()

Note that you need to add all cmake.definitions calls before calling cmake.configure()

Posted by Uli Köhler in C/C++, Conan

How to fix CMake Protobuf “FindThreads only works if either C or CXX language is enabled”

Problem:

When trying to configure your CMake project using

find_package(Protobuf REQUIRED)

you see an error message like

CMake Error at /usr/share/cmake-3.16/Modules/FindThreads.cmake:49 (message):
  FindThreads only works if either C or CXX language is enabled
Call Stack (most recent call first):
  /usr/share/cmake-3.16/Modules/FindProtobuf.cmake:420 (find_package)
  CMakeLists.txt:7 (find_package)

-- Configuring incomplete, errors occurred!

Solution:

You need to put your

project(MyProject)

line before the

find_package(Protobuf REQUIRED)

line. If you don’t have a project() line, create one.

Posted by Uli Köhler in C/C++, CMake

How to compile boost unit test program using CMake

Add this to your CMakeLists.txt:

#
# Compile test suite
#
find_package(Boost COMPONENTS system filesystem unit_test_framework REQUIRED)

add_executable(test_myprogram
    tests/MyTest.cpp
)
target_include_directories(test_myprogram PUBLIC "${CMAKE_CURRENT_LIST_DIR}/include")
target_compile_features(test_myprogram PRIVATE cxx_std_17)

target_link_libraries(test_myprogram
                      ${Boost_FILESYSTEM_LIBRARY}
                      ${Boost_SYSTEM_LIBRARY}
                      ${Boost_UNIT_TEST_FRAMEWORK_LIBRARY}
                      )
add_test(test_myprogram test_myprogram)
# make "make test" run the test program
add_custom_target(test
     DEPENDS myprogram
     COMMAND ./test_myprogram
)

In order to build the program and the test, run

make

In order to run the tests, use

make test
Posted by Uli Köhler in Boost, C/C++, CMake

How to fix CMake error Could not find a package configuration file provided by “boost_unit_test_framework”

Problem:

When compiling your CMake-based C++

CMake Error at /usr/lib/x86_64-linux-gnu/cmake/Boost-1.71.0/BoostConfig.cmake:117 (find_package):
  Could not find a package configuration file provided by
  "boost_unit_test_framework" (requested version 1.71.0) with any of the
  following names:

    boost_unit_test_frameworkConfig.cmake
    boost_unit_test_framework-config.cmake

  Add the installation prefix of "boost_unit_test_framework" to
  CMAKE_PREFIX_PATH or set "boost_unit_test_framework_DIR" to a directory
  containing one of the above files.  If "boost_unit_test_framework" provides
  a separate development package or SDK, be sure it has been installed.
Call Stack (most recent call first):
  /usr/lib/x86_64-linux-gnu/cmake/Boost-1.71.0/BoostConfig.cmake:182 (boost_find_component)
  /usr/share/cmake-3.16/Modules/FindBoost.cmake:443 (find_package)
  OCCUtils/CMakeLists.txt:58 (find_package)


-- Configuring incomplete, errors occurred!

Solution:

The error message is trying to tell you that you don’t have the boost unit test library installed (or CMake can’t find it).

On Ubuntu, for example, install it using

sudo apt -y install libboost-test-dev

On Windows you can install it using the prebuilt boost binaries for Windows.

Posted by Uli Köhler in C/C++, CMake

How to fix CMake error Could not find a package configuration file provided by “boost_filesystem”

Problem:

When compiling your CMake-based C++

CMake Error at /usr/lib/x86_64-linux-gnu/cmake/Boost-1.71.0/BoostConfig.cmake:117 (find_package):
  Could not find a package configuration file provided by "boost_filesystem"
  (requested version 1.71.0) with any of the following names:

    boost_filesystemConfig.cmake
    boost_filesystem-config.cmake

  Add the installation prefix of "boost_filesystem" to CMAKE_PREFIX_PATH or
  set "boost_filesystem_DIR" to a directory containing one of the above
  files.  If "boost_filesystem" provides a separate development package or
  SDK, be sure it has been installed.
Call Stack (most recent call first):
  /usr/lib/x86_64-linux-gnu/cmake/Boost-1.71.0/BoostConfig.cmake:182 (boost_find_component)
  /usr/share/cmake-3.16/Modules/FindBoost.cmake:443 (find_package)
  CMakeLists.txt:58 (find_package)

Solution:

The error message is trying to tell you that you don’t have the boost filesystem library installed (or CMake can’t find it).

On Ubuntu, for example, install it using

sudo apt -y install libboost-filesystem-dev

On Windows you can install it using the prebuilt boost binaries for Windows.

Posted by Uli Köhler in C/C++, CMake

CMake executable minimal example

This CMakeLists.txt builds an executable called main from main.cpp:

add_executable(main main.cpp)

 

Posted by Uli Köhler in CMake

Towards a docker-based build of C/C++ applications

Note: Based on this post I have published buildock on GitHub.

Many C/C++ programmers and project managers know the pain of creating a reproducible build environment for all developers: Works for me is a common meme not without a reason.

My approach is to dockerize not neccessarily the application itself but the build system, encapsulating both the specific compiler version and the system around it plus all required system-level libraries in a Docker image.

Take the obligatory Hello World in C++:

// main.cpp
#include <iostream>
using namespace std;

int main() {
    cout << "Hello, World!" << endl;
    return 0;
}

and the corresponding Makefile:

all:
        g++ -o helloworld main.cpp

How can we compile this simple project without installing a compiler and GNU make on the local computer (no cheating by using build servers allowed)?

Actually it’s rather simple:

docker run --user $(id -u):$(id -g) -v $PWD:/app -it ulikoehler/ubuntu-gcc-make make

Breaking it down:

  • docker run: Create a new docker container and run a command in it
  • --user $(id -u):$(id -g): This makes the docker container run with the current user’s ID and the current user’s group – both for preventing the compiler to create output files as root and to safeguard against some IT security risks. Also see How to run docker container as current user & group
  • -v $PWD:/app: Mount the current directory ($PWD) on /app in the container. Since the Dockerfile used to build the container contains the WORKDIR /app directive, whatever command we run in the container will by default be executed in the /app directory – and therefore in the current local directory on the host.
  • -it runs the container in interactive mode, i.e. keypressed are passed down to the command you are running. Also, this means that our command will only finish when the container has finished executing.
  • ulikoehler/ubuntu-gcc-make: This is the image we’re using for that example. It’s nothing more than an ubuntu:18.04 base image with build-essentials and make installed and WORKDIR set to /app
  • make: This is the command we’ll run in the container. You can use any command here, even no command is possible (in which case the container’s default command will be used – in case of ulikoehler/ubuntu-gcc-make that is CMD [ "/usr/bin/make" ])

Here’s the complete Dockerfile used to generate ulikoehler/ubuntu-gcc-make:

FROM ubuntu:18.04
RUN apt update && apt -y install build-essential make && rm -rf /var/lib/apt/lists/*
WORKDIR /app
CMD [ "/usr/bin/make" ]
Posted by Uli Köhler in Build systems, C/C++, Container, Docker

What is the CMake equivalent to AC_CHECK_FUNCS()?

With automake/m4 in configure.ac you use syntax like

AC_CHECK_FUNCS(atan2)

which defines HAVE_FDATASYNC if the function is available.

In CMake, you can use check_symbol_exists() for the same purpose like this:

cmake_minimum_required(VERSION 3.0)
include(CheckSymbolExists)

# Define executable
add_executable(myexe main.c)

# atan2 requires the math library to be linked
list(APPEND CMAKE_REQUIRED_LIBRARIES m)
check_symbol_exists(atan2 math.h HAVE_ATAN2)

# Add compile definitions if we have the library
if(HAVE_ATAN2)
    target_compile_definitions(myexe PRIVATE -DHAVE_ATAN2)
endif()

Note that check_symbol_exists() does not automatically add a preprocessor define but you have to do that manually (see the last block in the code shown above). While this might seem less comfortable at first, this approach provides you with much more flexibility on how to handle missing or available functions.

See the CMake check_symbol_exists() documentation for more details.

Posted by Uli Köhler in CMake

CMake check_symbol_exists() minimal example

cmake_minimum_required(VERSION 3.0)
include(CheckSymbolExists)

# Define executable
add_executable(myexe main.c)

# atan2 requires the math library to be linked
list(APPEND CMAKE_REQUIRED_LIBRARIES m)
check_symbol_exists(atan2 math.h HAVE_ATAN2)

# Add compile definitions if we have the library
if(HAVE_ATAN2)
    target_compile_definitions(myexe PRIVATE -DHAVE_ATAN2)
endif()
Posted by Uli Köhler in CMake

How to fix ‘Unknown CMake command “check_symbol_exists”‘

If you have CMake code using check_symbol_exists(...) like

list(APPEND CMAKE_REQUIRED_LIBRARIES m)
check_symbol_exists(atan2 math.h HAVE_ATAN2)

but you get an error message like

CMake Error at CMakeLists.txt:8 (check_symbol_exists):
  Unknown CMake command "check_symbol_exists".

-- Configuring incomplete, errors occurred!

you need to add

include(CheckSymbolExists)

near the top of your CMakeLists.txt (before your first call to check_symbol_exists()).

Posted by Uli Köhler in CMake

How to add boost::program_options to your CMake build

Simply add these lines to the end of your CMakeLists.txt and replace myTarget by the name of your build target (usually the first argument to add_executable(...) or add_library(...)):

# Include boost
find_package( Boost 1.30 COMPONENTS program_options REQUIRED )
target_include_directories( myTarget PRIVATE ${Boost_INCLUDE_DIR})
target_link_libraries( myTarget ${Boost_LIBRARIES} )

If you have multiple targets, copy & paste the last two lines for each target.

If you need a specific version of boost, replace 1.30 by the minimum version you need.

Posted by Uli Köhler in Boost, C/C++, CMake

How to build debug in CMake

If you want to build an executable / library with debug symbols in CMake, run

cmake -DCMAKE_BUILD_TYPE=Debug .
make

Conversely, if you want to build an executable / library in release mode, run

cmake -DCMAKE_BUILD_TYPE=Release .
make

 

Posted by Uli Köhler in C/C++, CMake

How to fix SDCC ‘at 1: warning 119: don’t know what to do with file ‘main.o’. file extension unsupported’

If you use SDCC to compile your C code for your microcontroller and you encounter an error message like this:

at 1: warning 119: don't know what to do with file 'main.o'. file extension unsupported

you have to configure your build system to use the .rel suffix for object files instead of the standard .o. SDCC expects built object files to have the .rel extension! See How to change CMake object file suffix from default “.o” for details on how to do that in CMake.

Posted by Uli Köhler in Build systems, Embedded