This is the .gitignore I use for most of my conan-built executable projects:
CMakeCache.txt CMakeFiles/ Makefile bin/ cmake_install.cmake conan.lock conanbuildinfo.cmake conanbuildinfo.txt conaninfo.txt graph_info.json
It is debatable whether you should include lock files such as conan.lock. My opinion is that in the development phase they should be ignored but reconsidered when entering into production service.
In the directory where you want to create the project, run (obviously, replace mypackageby the name of everywhere in our code!)
conan new mypackage/1.0.0 -s
-s is important here. It tells conan that the source is available in the project directory and it should not be pulled using git etc.
This will initialize a shared library project, which we will now modify to build an executable.
First, open src/CMakeLists.txt and change add_library() to add_executable(), for example
add_library(mypackage mypackage.cpp)
to
add_executable(mypackage mypackage.cpp)
Now we shall modify conanfile.py to properly build & install the executable:
def package(self):
self.copy("*.h", dst="include", src="src")
self.copy("*.lib", dst="lib", keep_path=False)
self.copy("*.dll", dst="bin", keep_path=False)
self.copy("*.dylib*", dst="lib", keep_path=False)
self.copy("*.so", dst="lib", keep_path=False)
self.copy("*.a", dst="lib", keep_path=False)
def package_info(self):
self.cpp_info.libs = ["NoxecoDB"]
with
def package(self):
self.copy("mypackage", src="bin", dst="bin", keep_path=False)
def package_info(self):
self.env_info.PATH = os.path.join(self.package_folder, "bin")
def deploy(self):
self.copy("mypackage", dst="bin", src="bin")
and add
import os.path
to the top of the file
Now let’s add a main() function to src/mypackage.cpp. Replace the file’s content with
#include <iostream>
int main(int argc, char** argv) {
std::cout << "Hello World!" <<std::endl;
}
Now it’s time to install the dependencies & build the project using
conan install . && conan build .
The executable will be in
bin/mypackage
You can run it using
./bin/mypackage
which will print
Hello World!
I also recommend to add this .gitignore:
CMakeCache.txt CMakeFiles/ Makefile bin/ cmake_install.cmake conan.lock conanbuildinfo.cmake conanbuildinfo.txt conaninfo.txt graph_info.json
When running
conan install .
you see ERROR: Missing binary error messages like this:
Installing (downloading, building) binaries... ERROR: Missing binary: cpr/1.6.2:76fe60a9d5c829a2384b0f578695b5a6357b8acc ERROR: Missing binary: gtest/cci.20210126:c37dc23725d84483088a68c29e2dd7122c328359 ERROR: Missing binary: jsoncpp/1.9.4:718278bac9f92b77a9a44bfbe1aa00d1c8344d51 ERROR: Missing binary: libcurl/7.78.0:d287dc966931230205222ceabf47400733e72fa3 ERROR: Missing binary: openssl/1.1.1l:c3baf9fae083edda2e0c5ef3337b6a111016a898 ERROR: Missing binary: zlib/1.2.11:c3baf9fae083edda2e0c5ef3337b6a111016a898
Use the --build=missing flag for conan install to enable building the dependencies for which no binaries are available:
conan install . --build=missing
Configuration:
[settings]
arch=armv8
arch_build=armv8
build_type=Release
compiler=gcc
compiler.libcxx=libstdc++
compiler.version=9
os=Linux
os_build=Linux
[options]
[build_requires]
[env]
openssl/1.1.1l: Not found in local cache, looking in remotes...
openssl/1.1.1l: Trying with 'conancenter'...
Downloading conanmanifest.txt completed [0.26k]
Downloading conanfile.py completed [40.47k]
Downloading conan_export.tgz completed [0.25k]
Decompressing conan_export.tgz completed [0.00k]
openssl/1.1.1l: Downloaded recipe revision 0
cpr/1.6.2: Not found in local cache, looking in remotes...
cpr/1.6.2: Trying with 'conancenter'...
Downloading conanmanifest.txt completed [0.25k]
Downloading conanfile.py completed [9.62k]
Downloading conan_export.tgz completed [0.30k]
Decompressing conan_export.tgz completed [0.00k]
cpr/1.6.2: Downloaded recipe revision 0
WARN: cpr/1.6.2: requirement libcurl/7.80.0 overridden by elasticlient/0.2 to libcurl/7.78.0
libcurl/7.78.0: Not found in local cache, looking in remotes...
libcurl/7.78.0: Trying with 'conancenter'...
Downloading conanmanifest.txt completed [0.70k]
Downloading conanfile.py completed [27.11k]
Downloading conan_export.tgz completed [0.23k]
Decompressing conan_export.tgz completed [0.00k]
libcurl/7.78.0: Downloaded recipe revision 0
jsoncpp/1.9.4: Not found in local cache, looking in remotes...
jsoncpp/1.9.4: Trying with 'conancenter'...
Downloading conanmanifest.txt completed [0.65k]
Downloading conanfile.py completed [4.90k]
Downloading conan_export.tgz completed [0.25k]
Decompressing conan_export.tgz completed [0.00k]
jsoncpp/1.9.4: Downloaded recipe revision 0
gtest/cci.20210126: Not found in local cache, looking in remotes...
gtest/cci.20210126: Trying with 'conancenter'...
Downloading conanmanifest.txt completed [0.39k]
Downloading conanfile.py completed [8.14k]
Downloading conan_export.tgz completed [0.32k]
Decompressing conan_export.tgz completed [0.00k]
gtest/cci.20210126: Downloaded recipe revision 0
conanfile.py (elasticlient/0.2): Installing package
Requirements
cpr/1.6.2 from 'conancenter' - Downloaded
jsoncpp/1.9.4 from 'conancenter' - Downloaded
libcurl/7.78.0 from 'conancenter' - Downloaded
openssl/1.1.1l from 'conancenter' - Downloaded
zlib/1.2.11 from 'conancenter' - Cache
Packages
cpr/1.6.2:76fe60a9d5c829a2384b0f578695b5a6357b8acc - Missing
jsoncpp/1.9.4:718278bac9f92b77a9a44bfbe1aa00d1c8344d51 - Missing
libcurl/7.78.0:d287dc966931230205222ceabf47400733e72fa3 - Missing
openssl/1.1.1l:c3baf9fae083edda2e0c5ef3337b6a111016a898 - Missing
zlib/1.2.11:c3baf9fae083edda2e0c5ef3337b6a111016a898 - Missing
Build requirements
gtest/cci.20210126 from 'conancenter' - Downloaded
Build requirements packages
gtest/cci.20210126:c37dc23725d84483088a68c29e2dd7122c328359 - Missing
Installing (downloading, building) binaries...
ERROR: Missing binary: cpr/1.6.2:76fe60a9d5c829a2384b0f578695b5a6357b8acc
ERROR: Missing binary: gtest/cci.20210126:c37dc23725d84483088a68c29e2dd7122c328359
ERROR: Missing binary: jsoncpp/1.9.4:718278bac9f92b77a9a44bfbe1aa00d1c8344d51
ERROR: Missing binary: libcurl/7.78.0:d287dc966931230205222ceabf47400733e72fa3
ERROR: Missing binary: openssl/1.1.1l:c3baf9fae083edda2e0c5ef3337b6a111016a898
ERROR: Missing binary: zlib/1.2.11:c3baf9fae083edda2e0c5ef3337b6a111016a898
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]
In order to list local conan packages, run
conan search
$ 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
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", )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.
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", )
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")
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
If you want to create a new conan build recipe for a package that already exists, use
conan new hello/0.1
conan new hello/0.1 -t
More info: See packaging docs
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()
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!
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.
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
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!
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.
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)
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.
This CMakeLists.txt builds an executable called main from main.cpp:
add_executable(main main.cpp)
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.cppHow 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 /appmake: 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" ]
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.
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()
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()).
if/else/endif looks like this in CMake:
if(myvar)
message("if")
else()
message("else")
endif()