Hello Folks!
Across this forum and the GRPC GitHub issue archives, I don't think I see
any guide from the maintainers on how to cross-compile GRPC and the
dependencies.
*Background*: For an embedded project, I was trying to get GRPC to run on
Linux/ARM. I am *able to* successfully cross-compile GRPC, Protobuf and
build some applications to run on the target. However, I am still not sure
of the exact order of steps and it seems to me like black magic! The
Makefile is at a whopping 25k LoC! The section that deals with
cross-compiling is very small. Thankfully, I found [1], [2] and [3] very
helpful but I still have a bunch of things which I don't quite understand
and how the dependencies are resolved.
Here are some of the questions I have and would be eternally grateful if
somebody can help me better understand :)
*NOTE*:
- In this case, --host=arm-linux-gnueabihf --build=x86_64-pc-linux-gnu
- I have ProtoBuf and the protoc compiler (with all the GRPC plugins
installed on my build machine)
1. I don't want to use BoringSSL and would prefer using OpenSSL. The
reason being that for purposes of "security conformance" (certifications
such as NIST's FIPS or Common Criteria), it's better (we've already
invested efforts to "sanitize" OpenSSL)
1. I got OpenSSL from GitHub (https://github.com/openssl/openssl) and
cross-compiled them for the Linux/ARM
2. Produced all the *libssl* and *libcrypto* .so and .a libraries
2. I am able to cross-compile ProtoBuf for Linux/ARM and get all the .so
and .a libraries
3. It also seems that for the "*make run_dep_checks*" to work, I had to
*separately* individually cross-compile (for Linux/ARM) the following
projects:
1. gperftools (https://github.com/gperftools/gperftools) - For the
"-l profiler"
2. zlib (grpc/third_party/zlib already as part of the grpc 'sub
module')
3. c-ares (grpc/third_party/cares/cares) - For the "-l cares"
4. protobuf (grpc/third_party/protobuf)
5. OpenSSL - Like I mentioned in (1).(1) above
4. So with all these "dependencies" already compiled for my Linux/ARM
target, when I try compiling the GRPC source, I am unable to figure out a
few things
1. With the right GRPC_CROSS_LDOPTS pointing to the paths of the
compiled dependencies above, the Makefile figures out that it doesn't
need
to build BoringSSL --> *That's great!*
2. I also use the *EMBED_OPENSSL=false* flag --> *Is this correct?*
3. As per [4], should I also be using *HAS_SYSTEM_OPENSSL_ALPN=false
HAS_SYSTEM_OPENSSL_NPN=true*?
4. I'm also using the following flags: *GRPC_CROSS_COMPILE=true
HAS_PKG_CONFIG=false GRPC_CROSS_AROPTS="cr --target=elf32-little"*
5. One of the problems is that the compilation skips compiling
Protobuf (as needed - since it's already compiled), *BUT*, it tries
to build all the GRPC language plugins using the arm-linux-gcc toolchain
and this invariably fails on the build machine host since the CPU
architectures don't match --> *How can I skip the building of the
GRPC language plugins? *Using *HAS_SYSTEM_PROTOBUF=false* and this
skips the language plugins, *BUT* it re-builds the entire protobuf
source again :|
1. How can I avoid re-building protobuf from source again during
GRPC building, avoid building protoc and the GRPC plugins (since it's
already available on the host)? What make flags should I use?
This is what I'm using to cross-compile and works - barring that the
protobuf source is again re-compiled (due to the
*HAS_SYSTEM_PROTOBUF=false *flag)
GRPC_CROSS_COMPILE=true HAS_PKG_CONFIG=false EMBED_OPENSSL=false
GRPC_CROSS_AROPTS="cr --target=elf32-little" HAS_SYSTEM_PROTOBUF=false
PROTOBUF_CONFIG_OPTS="--host=arm-linux-gnueabihf
--build=x86_64-pc-linux-gnu --with-protoc=/usr/local/bin/protoc"
HOST_CC=gcc HOST_CXX=g++ HOST_LD=gcc HOST_LDXX=g++
HOST_LDLIBSXX="-L<path-to-the-build-machine's-protobuf-libs>"
HOST_LDLIBS_PROTOC="-L/usr/local/lib -lprotoc -lprotobuf"
CC=arm-linux-gnueabihf-gcc CFLAGS="-I<path-to-openssl-header-files>
-I<path-to-cares-header-files> -I<path-to-gperftools-header-files>
-I<path-to-zlib-header-files>" CXX=arm-linux-gnueabihf-g++
CXXFLAGS="-I<path-to-openssl-header-files> -I<path-to-cares-header-files>
-I<path-to-gperftools-header-files> -I<path-to-zlib-header-files>"
RANLIB=arm-linux-gnueabihf-ranlib LD=arm-linux-gnueabihf-gcc
LDXX=arm-linux-gnueabihf-g++ AR=arm-linux-gnueabihf-ar
GRPC_CROSS_LDOPTS="-L<path-to-cares-compiled-Linux/ARM-libs>
-L<path-to-gperftools-compiled-Linux/ARM-libs>
-L<path-to-zlib-compiled-Linux/ARM-libs>
-L<path-to-openssl-compiled-Linux/ARM-libs>
-L<path-to-protobuf-compiled-Linux/ARM-libs>" make
(Apologies for the long post!)
Oh, another thing I figured out was that it's easier (in fact, the Makefile
assumes this) to use gcc/arm-linux-gnueabihf-gcc and
g++/arm-linux-gnueabihf-g++ for the linker (instead of invoking
ld/arm-linux-gnueabihf-ld).
*Reference*:
[1] https://github.com/grpc/grpc/issues/9719
[2] https://groups.google.com/forum/#!topic/grpc-io/848KwP13fPc
[3] https://github.com/grpc/grpc/issues/13436
[4] https://github.com/grpc/grpc/issues/11655
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