How to use Bazel as a build tool in Conan.io - c++

Question

I am trying to use Conan for package management and Bazel as build tool for my C++ Codes. The reason I am using conan is because JFrog Artifactory supports it, which I am using as my Artifactory Repository.
To do that I came up with the following plan :
$/home/mytimer=> ls -lrt
0 Sep 25 11:57 WORKSPACE
4096 Sep 25 12:00 build/
4096 Sep 25 12:02 main/
$/home/mytimer=> ls -l main
total 4
60 Sep 25 12:02 BUILD
61 Sep 25 11:56 conanfile.txt
955 Sep 25 11:56 timer.cpp
$/home/mytimer=> ls -l build
total 8
1266 Sep 25 12:00 conanbuildinfo.gcc
1875 Sep 25 12:00 conaninfo.txt
( This is after I executed conan --install ../main )
$/home/mytimer=> cat cat main/conanfile.txt
[requires]
Poco/1.7.8p3#pocoproject/stable
[generators]
gcc
$/home/mytimer=>cat build/conanbuildinfo.gcc
-DPOCO_STATIC=ON -DPOCO_NO_AUTOMATIC_LIBS -I"/home/.conan/data/Poco/1.7.8p3/pocoproject/stable/package/da23483d46b7229cbae8615ce1ea2594635f3a5f/include" -I"/home/.conan/data/OpenSSL/1.0.2l/conan/stable/package/c8dc3f0797f6d24f3c80634ae2854ddf9ee34334/include" -I"/home/.conan/data/zlib/1.2.11/conan/stable/package/82b1dd29b2e9143665c77ef477100c690d719cbf/include" -Wl,-rpath="/home/.conan/data/Poco/1.7.8p3/pocoproject/stable/package/da23483d46b7229cbae8615ce1ea2594635f3a5f/lib" -Wl,-rpath="/home/.conan/data/OpenSSL/1.0.2l/conan/stable/package/c8dc3f0797f6d24f3c80634ae2854ddf9ee34334/lib" -Wl,-rpath="/home/.conan/data/zlib/1.2.11/conan/stable/package/82b1dd29b2e9143665c77ef477100c690d719cbf/lib" -L"/home/.conan/data/Poco/1.7.8p3/pocoproject/stable/package/da23483d46b7229cbae8615ce1ea2594635f3a5f/lib" -L"/home/.conan/data/OpenSSL/1.0.2l/conan/stable/package/c8dc3f0797f6d24f3c80634ae2854ddf9ee34334/lib" -L"/home/.conan/data/zlib/1.2.11/conan/stable/package/82b1dd29b2e9143665c77ef477100c690d719cbf/lib" -lPocoUtil -lPocoMongoDB -lPocoNet -lPocoNetSSL -lPocoCrypto -lPocoData -lPocoDataSQLite -lPocoZip -lPocoXML -lPocoJSON -lPocoFoundation -lpthread -lrt -lssl -lcrypto -ldl -lz -D_GLIBCXX_USE_CXX11_ABI=0 -m64 -s -DNDEBUGdevc
$/home/mytimer=> cat build/conaninfo.txt
[settings]
arch=x86_64
build_type=Release
compiler=gcc
compiler.libcxx=libstdc++
compiler.version=6.3
os=Linux
[requires]
Poco/1.Y.Z
[options]
[full_settings]
arch=x86_64
build_type=Release
compiler=gcc
compiler.libcxx=libstdc++
compiler.version=6.3
os=Linux
[full_requires]
OpenSSL/1.0.2l#conan/stable:c8dc3f0797f6d24f3c80634ae2854ddf9ee34334
Poco/1.7.8p3#pocoproject/stable:da23483d46b7229cbae8615ce1ea2594635f3a5f
zlib/1.2.11#conan/stable:82b1dd29b2e9143665c77ef477100c690d719cbf
[full_options]
OpenSSL:386=False
OpenSSL:no_asm=False
OpenSSL:no_bf=False
OpenSSL:no_cast=False
OpenSSL:no_des=False
OpenSSL:no_dh=False
OpenSSL:no_dsa=False
OpenSSL:no_hmac=False
OpenSSL:no_md2=False
OpenSSL:no_md5=False
OpenSSL:no_mdc2=False
OpenSSL:no_rc2=False
OpenSSL:no_rc4=False
OpenSSL:no_rc5=False
OpenSSL:no_rsa=False
OpenSSL:no_sha=False
OpenSSL:no_sse2=False
OpenSSL:no_threads=False
OpenSSL:no_zlib=False
OpenSSL:shared=False
Poco:cxx_14=False
Poco:enable_apacheconnector=False
Poco:enable_cppparser=False
Poco:enable_crypto=True
Poco:enable_data=True
Poco:enable_data_mysql=False
Poco:enable_data_odbc=False
Poco:enable_data_sqlite=True
Poco:enable_json=True
Poco:enable_mongodb=True
Poco:enable_net=True
Poco:enable_netssl=True
Poco:enable_netssl_win=True
Poco:enable_pagecompiler=False
Poco:enable_pagecompiler_file2page=False
Poco:enable_pdf=False
Poco:enable_pocodoc=False
Poco:enable_sevenzip=False
Poco:enable_tests=False
Poco:enable_util=True
Poco:enable_xml=True
Poco:enable_zip=True
Poco:force_openssl=True
Poco:poco_unbundled=False
Poco:shared=False
zlib:shared=False
[scope]
dev=True
[recipe_hash]
[env]
$/home/mytimer=> cat main/BUILD
cc_binary(
name = "timer",
srcs = ["timer.cpp"],
)
Now, I want to build the mytimer project using bazel as something like this :
$/home/mytimer=> bazel build --(some options) //main:timer
What should this some options be , so that bazel can read conanbuildinfo.gcc and use it to create the executable file ?

Answer 1

I used the genrule() feature of bazel to solve my problem in this way :
$/home/mytimer=> cat main/BUILD
genrule(
name = "timer",
outs = ["timer.out"],
cmd = "g++ /home/mytimer/main/timer.cpp#/home/mytimer/build/conanbuildinfo.gcc -o $# ",
)
/home/mytime=> bazel build -s //main:timer
WARNING: ignoring http_proxy in environment.
WARNING: Output base '/home/.cache/bazel/_bazel_user/274fa1325d85b25c2722794ea' is on NFS. This may lead to surprising failures and undetermined behavior.
INFO: Found 1 target...
>>>>> # //main:timer [action 'Executing genrule //main:timer']
(cd /home/.cache/bazel/_bazel_user/274fa1325d85b25c2722614/execroot/__main__ && \
exec env - \
LD_LIBRARY_PATH=<library paths>
PATH=<all other paths>
/bin/bash -c 'source external/bazel_tools/tools/genrule/genrule-setup.sh; g++ /home/bazel/examples/cpp-tutorial/mytimer/main/timer.cpp #/home/bazel/examples/cpp-tutorial/mytimer/build/conanbuildinfo.gcc -o bazel-out/local-fastbuild/genfiles/main/timer.out ')
Target //main:timer up-to-date:
bazel-genfiles/main/timer.out
INFO: Elapsed time: 1.050s, Critical Path: 0.50s
/home/mytime=> ls -lrt bazel-out/local-fastbuild/genfiles/main/
total 212
212000 Sep 26 14:42 timer.out
/home/mytime=> ./bazel-out/local-fastbuild/genfiles/main/timer.out
Callback called after 249 milliseconds.
Callback called after 749 milliseconds.
Callback called after 1249 milliseconds.
Callback called after 1749 milliseconds.
Callback called after 2249 milliseconds.
Callback called after 2749 milliseconds.
^C
So, by using genrule() feature, we can execute any shell command in bazel. Although this is not a so-called "bazel" way to generate artifacts (genrule() to bazel is same as "goto" command to C/C++ ), in this scenario, I do not see any other option to solve this issue.

Answer 2

You could also create a custom rule: https://docs.bazel.build/versions/master/skylark/rules.html for this. Ideally you would use a Skylark api to the C++ rules, to prevent reimplementing everything that C++ rules already do, but unfortunately that api is not yet finished (October 2017). I think the best tracking bug is https://github.com/bazelbuild/bazel/issues/1624.