diff options
Diffstat (limited to 'doc/being-consumed-by-cmake.org')
-rw-r--r-- | doc/being-consumed-by-cmake.org | 165 |
1 files changed, 165 insertions, 0 deletions
diff --git a/doc/being-consumed-by-cmake.org b/doc/being-consumed-by-cmake.org new file mode 100644 index 0000000..86c1825 --- /dev/null +++ b/doc/being-consumed-by-cmake.org @@ -0,0 +1,165 @@ +* Being consumed by CMake + +To support libraries built with JustBuild to be consumed by CMake, the rule +~["CC", "install-with-deps"]~ can be used. This rule will install the library's +artifacts, its public headers, and a pkg-config file, which can be used by CMake +to properly consume the library. + +In this example, we show how to build and install the ~ssl~ library with +JustBuild, so it can be picked up and used by CMake afterwards. + +** Example: Build and install the ~ssl~ Library with JustBuild + +First make sure that ~just~, ~just-mr~, and ~just-import-git~ are available in +your ~PATH~. Then, define a new workspace by creating the ~ROOT~ marker. + +#+BEGIN_SRC sh +$ touch ROOT +#+END_SRC + +The ~ssl~ library that we want to use is a defined dependency of the JustBuild +repository ~just/ssl~. To define a repository for that library, create the +following ~repos.template.json~ file. + +#+SRCNAME: repos.template.json +#+BEGIN_SRC js +{ "main": "ssl" +, "repositories": + { "ssl": + { "repository": {"type": "file", "path": "."} + , "bindings": {"rules": "rules-cc", "just-ssl": "just/ssl"} + } + } +} +#+END_SRC + +and import the ~rules-cc~ and JustBuild repository, including its dependency +~just/ssl~, via: + +#+BEGIN_SRC sh +$ cat repos.template.json \ + | just-import-git -C - --as just -b master https://github.com/just-buildsystem/justbuild \ + | just-import-git -C - --as rules-cc -b master https://github.com/just-buildsystem/rules-cc \ + > repos.json +$ +#+END_SRC + +Next, the following ~TARGETS~ file needs to be provided. + +#+SRCNAME: TARGETS +#+BEGIN_SRC js +{ "ssl-lib": + { "type": ["@", "rules", "CC", "library"] + , "name": ["ssl"] + , "deps": [["@", "just-ssl", "", "ssl"]] + } +, "ssl-pkg": + {"type": ["@", "rules", "CC", "install-with-deps"], "targets": ["ssl-lib"]} +} +#+END_SRC + +The library target ~ssl-lib~ specifies the name ~"ssl"~ (also used as package +name) and a dependency on the ~ssl~ library from ~just-ssl~. Note that although +this library target is merely a "wrapper" (header-only library without headers), +it could equally well be a full-blown library target. Furthermore, the package +target ~ssl-pkg~ installs the ~ssl-lib~ target including its dependencies and +generates a pkg-config file that can be later used by CMake. + +Finally, the ~ssl-pkg~ target can be built and installed to a specific ~PREFIX~ +(note that ~OS~ and ~ARCH~ must be set as well). + +#+BEGIN_SRC sh +$ export PREFIX=/tmp/just_ssl +$ just-mr install -D'{"OS":"linux", "ARCH":"x64_64", "PREFIX":"'$PREFIX'"}' -o $PREFIX ssl-pkg +INFO: Requested target is [["@","ssl","","ssl-pkg"],{"ARCH":"x64_64","OS":"linux","PREFIX":"/tmp/just_ssl"}] +INFO: Analysed target [["@","ssl","","ssl-pkg"],{"ARCH":"x64_64","OS":"linux","PREFIX":"/tmp/just_ssl"}] +INFO: Export targets found: 0 cached, 2 uncached, 0 not eligible for caching +INFO: Discovered 269 actions, 3 trees, 1 blobs +INFO: Building [["@","ssl","","ssl-pkg"],{"ARCH":"x64_64","OS":"linux","PREFIX":"/tmp/just_ssl"}]. +PROG: [ 79%] 0 cached, 215 run, 8 processing (["@","just/ssl","","crypto-lib"]#105, ...). +INFO: Processed 269 actions, 0 cache hits. +INFO: Artifacts can be found in: + /tmp/just_ssl/include/openssl/aead.h [6d78db27d24746b39eacc20374697476e080c9f6:21054:f] + ... + /tmp/just_ssl/lib/libcrypto.a [df64da43f0168a717d09d609bf0c631d29c86b61:2336092:f] + /tmp/just_ssl/lib/libssl.a [77d2c2bfbe3ef3608895c854f1d1f6e1c200efd0:852620:f] + /tmp/just_ssl/share/pkgconfig/ssl.pc [9b69c758430f5b5fb6ff7a9b1f1ffc89471509af:406:f] +$ +#+END_SRC + +** Example: Consume the installed ~ssl~ Library with CMake + +As an example, a minimal ~main.c~ file is created that depends on the ~ssl~ +library. + +#+SRCNAME: main.c +#+BEGIN_SRC C +#include <openssl/evp.h> + +int main(int argc, char** argv) { + OpenSSL_add_all_algorithms(); + return 0; +} +#+END_SRC + +In the ~CMakeLists.txt~ file, the ~pkg_check_modules()~ macro can be used to +determine the compile and linker flags needed to consume our ~ssl~ library with +CMake. + +#+SRCNAME: CMakeLists.txt +#+BEGIN_SRC cmake +cmake_minimum_required(VERSION 3.1) + +project(test_ssl) + +find_package(PkgConfig REQUIRED) +pkg_check_modules(SSL REQUIRED ssl) + +add_executable(main main.c) +target_include_directories(main PRIVATE ${SSL_INCLUDE_DIRS}) +target_compile_options(main PRIVATE ${SSL_CFLAGS_OTHER}) +target_link_directories(main PRIVATE ${SSL_LIBRARY_DIRS}) +target_link_libraries(main PRIVATE ${SSL_LDFLAGS_OTHER} ${SSL_LIBRARIES}) +#+END_SRC + +Note that ~${SSL_LDFLAGS_OTHER}~ can be omitted if the ~ssl-pkg~ target was +defined with a non-empty value for the field ~"flat-libs"~ (see rule +documentation of ~["CC", "install-with-deps"]~). + +Finally, when running CMake, make sure to set the ~CMAKE_PREFIX_PATH~ to the +previously used install prefix in order to successfully find the installed ~ssl~ +library and its pkg-config file. + +#+BEGIN_SRC sh +$ cmake -DCMAKE_PREFIX_PATH=/tmp/just_ssl -S . -B /tmp/test_ssl +-- The C compiler identification is GNU 10.2.1 +-- The CXX compiler identification is GNU 10.2.1 +-- Detecting C compiler ABI info +-- Detecting C compiler ABI info - done +-- Check for working C compiler: /usr/bin/cc - skipped +-- Detecting C compile features +-- Detecting C compile features - done +-- Detecting CXX compiler ABI info +-- Detecting CXX compiler ABI info - done +-- Check for working CXX compiler: /usr/bin/c++ - skipped +-- Detecting CXX compile features +-- Detecting CXX compile features - done +-- Found PkgConfig: /usr/bin/pkg-config (found version "0.29.2") +-- Checking for module 'ssl' +-- Found ssl, version unknown +-- Configuring done +-- Generating done +-- Build files have been written to: /tmp/test_ssl +$ cmake --build /tmp/test_ssl +[ 50%] Building CXX object CMakeFiles/main.dir/main.c.o +[100%] Linking CXX executable main +[100%] Built target main +$ +#+END_SRC + +Note that if the package is moved to a different location, the ~prefix~ variable +within the pkg-config file ~share/pkgconfig/ssl.pc~ must be updated as well. +Alternatively, CMake can be instructed to automatically guess the correct prefix +by setting the variable ~PKG_CONFIG_ARGN~ to ~"--define-prefix"~ (either on the +command line or in the ~CMakeLists.txt~). However, this is a fairly recent CMake +feature and requires at least CMake version 3.22. |