Cross compiling on android failed

[hanwencheng]

System: Ubuntu 18.04 LTS on Windows WSL2

Following the guide here I could successfully compile Substrate node, but failing on compiling Kusama 0.7.3 (on master branch)

compiled with command

cargo build --target=aarch64-linux-android --release --bins --no-default-features

Get error

error[E0308]: mismatched types
   --> /home/hanwen/.cargo/registry/src/github.com-1ecc6299db9ec823/nix-0.10.0/src/sys/signal.rs:378:41
    |
378 |             SigHandler::SigAction(_) => (flags | SaFlags::SA_SIGINFO).bits(),
    |                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `i32`, found `u32`
    |
help: you can convert an `u32` to `i32` and panic if the converted value wouldn't fit
    |
378 |             SigHandler::SigAction(_) => (flags | SaFlags::SA_SIGINFO).bits().try_into().unwrap(),
    |                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0308]: mismatched types
   --> /home/hanwen/.cargo/registry/src/github.com-1ecc6299db9ec823/nix-0.10.0/src/sys/signal.rs:387:28
    |
387 |         SaFlags::from_bits(self.sigaction.sa_flags).unwrap()
    |                            ^^^^^^^^^^^^^^^^^^^^^^^ expected `u32`, found `i32`
    |
help: you can convert an `i32` to `u32` and panic if the converted value wouldn't fit
    |
387 |         SaFlags::from_bits(self.sigaction.sa_flags.try_into().unwrap()).unwrap()
    |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0308]: mismatched types
   --> /home/hanwen/.cargo/registry/src/github.com-1ecc6299db9ec823/nix-0.10.0/src/sys/socket/mod.rs:800:29
    |
800 |         libc::bind(fd, ptr, len as c_int)
    |                             ^^^^^^^^^^^^ expected `u32`, found `i32`
    |
help: you can convert an `i32` to `u32` and panic if the converted value wouldn't fit
    |
800 |         libc::bind(fd, ptr, (len as c_int).try_into().unwrap())
    |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

   Compiling mio-extras v2.0.6
   Compiling sha2 v0.8.1
   Compiling sha-1 v0.8.2
   Compiling sha3 v0.8.2
   Compiling hmac v0.7.1
   Compiling pbkdf2 v0.3.0
error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0308`.
error: could not compile `nix`.
warning: build failed, waiting for other jobs to finish...
error: build failed

[tomaka]

The shared_memory library depends on a version old version of nix.
cc elast0ny/shared_memory#32

Ideally we shouldn't introduce even more platform-specific code, but as a temporary fix it is possible to disable shared_memory on Android:

diff --git a/parachain/Cargo.toml b/parachain/Cargo.toml
index 48aae981..e4dddac8 100644
--- a/parachain/Cargo.toml
+++ b/parachain/Cargo.toml
@@ -24,7 +24,7 @@ sp-io = { git = "https://github.com/paritytech/substrate", branch = "master", op
 parking_lot = { version = "0.10.0", optional = true }
 log = { version = "0.4.8", optional = true }
 
-[target.'cfg(not(target_os = "unknown"))'.dependencies]
+[target.'cfg(not(any(target_os = "android", target_os = "unknown")))'.dependencies]
 shared_memory = { version = "0.10.0", optional = true }
 
 [features]
diff --git a/parachain/src/wasm_executor/mod.rs b/parachain/src/wasm_executor/mod.rs
index 64c27278..2b64eb3b 100644
--- a/parachain/src/wasm_executor/mod.rs
+++ b/parachain/src/wasm_executor/mod.rs
@@ -101,7 +101,7 @@ pub enum Error {
 	#[display(fmt = "WASM worker error: {}", _0)]
 	External(String),
 	#[display(fmt = "Shared memory error: {}", _0)]
-	#[cfg(not(target_os = "unknown"))]
+	#[cfg(not(any(target_os = "android", target_os = "unknown")))]
 	SharedMem(shared_memory::SharedMemError),
 }
 
diff --git a/parachain/src/wasm_executor/validation_host.rs b/parachain/src/wasm_executor/validation_host.rs
index 84be3dee..0f123349 100644
--- a/parachain/src/wasm_executor/validation_host.rs
+++ b/parachain/src/wasm_executor/validation_host.rs
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
 
-#![cfg(not(target_os = "unknown"))]
+#![cfg(not(any(target_os = "android", target_os = "unknown")))]
 
 use std::{process, env, sync::Arc, sync::atomic, mem};
 use codec::{Decode, Encode, EncodeAppend};

[hanwencheng]

With these patches, I got the following error

error: failed to run custom build command for `jemalloc-sys v0.3.2`

Caused by:
  process didn't exit successfully: `/home/hanwen/Projects/polkadot/target/release/build/jemalloc-sys-325c06c5496cd499/build-script-build` (exit code: 101)
--- stdout
TARGET=aarch64-linux-android
HOST=x86_64-unknown-linux-gnu
NUM_JOBS=12
OUT_DIR="/home/hanwen/Projects/polkadot/target/aarch64-linux-android/release/build/jemalloc-sys-b79acd8a819a4581/out"
BUILD_DIR="/home/hanwen/Projects/polkadot/target/aarch64-linux-android/release/build/jemalloc-sys-b79acd8a819a4581/out/build"
SRC_DIR="/home/hanwen/.cargo/registry/src/github.com-1ecc6299db9ec823/jemalloc-sys-0.3.2"
OPT_LEVEL = Some("3")
TARGET = Some("aarch64-linux-android")
HOST = Some("x86_64-unknown-linux-gnu")
CC_aarch64-linux-android = None
CC_aarch64_linux_android = Some("/home/hanwen/Library/android-ndk-r21/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android29-clang")
CFLAGS_aarch64-linux-android = None
CFLAGS_aarch64_linux_android = Some("-std=gnu11 -fPIC -D OS_ANDROID -D ANDROID")
CRATE_CC_NO_DEFAULTS = None
DEBUG = Some("false")
CC="/home/hanwen/Library/android-ndk-r21/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android29-clang"
CFLAGS="-O3 -ffunction-sections -fdata-sections -fPIC --target=aarch64-linux-android -std=gnu11 -fPIC -D OS_ANDROID -D ANDROID"
JEMALLOC_REPO_DIR="jemalloc"
JEMALLOC_SRC_DIR="/home/hanwen/Projects/polkadot/target/aarch64-linux-android/release/build/jemalloc-sys-b79acd8a819a4581/out/jemalloc"
cargo:rustc-cfg=prefixed
--with-jemalloc-prefix=_rjem_
running: "sh" "/home/hanwen/Projects/polkadot/target/aarch64-linux-android/release/build/jemalloc-sys-b79acd8a819a4581/out/jemalloc/configure" "--disable-cxx" "--with-jemalloc-prefix=_rjem_" "--with-private-namespace=_rjem_" "--host=aarch64-linux-android" "--build=x86_64-unknown-linux-gnu" "--prefix=/home/hanwen/Projects/polkadot/target/aarch64-linux-android/release/build/jemalloc-sys-b79acd8a819a4581/out"
checking for xsltproc... false
checking for aarch64-linux-android-gcc... /home/hanwen/Library/android-ndk-r21/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android29-clang
checking whether the C compiler works... no

--- stderr
configure: error: in `/home/hanwen/Projects/polkadot/target/aarch64-linux-android/release/build/jemalloc-sys-b79acd8a819a4581/out/build':
configure: error: C compiler cannot create executables
See `config.log' for more details
thread 'main' panicked at 'command did not execute successfully: "sh" "/home/hanwen/Projects/polkadot/target/aarch64-linux-android/release/build/jemalloc-sys-b79acd8a819a4581/out/jemalloc/configure" "--disable-cxx" "--with-jemalloc-prefix=_rjem_" "--with-private-namespace=_rjem_" "--host=aarch64-linux-android" "--build=x86_64-unknown-linux-gnu" "--prefix=/home/hanwen/Projects/polkadot/target/aarch64-linux-android/release/build/jemalloc-sys-b79acd8a819a4581/out"
expected success, got: exit code: 77', /home/hanwen/.cargo/registry/src/github.com-1ecc6299db9ec823/jemalloc-sys-0.3.2/build.rs:392:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

warning: build failed, waiting for other jobs to finish...

[tomaka]

That's unrelated to this issue

[hanwencheng]

With parity-util-mem = { version = "*", default-features = false, features = [] } in ./Cargo.toml

has error of

error[E0425]: cannot find function `iterate_sockets_info` in this scope
  --> /home/hanwen/.cargo/registry/src/github.com-1ecc6299db9ec823/netstat2-0.8.1/src/integrations/shared_api.rs:11:5
   |
7  | / pub fn get_sockets_info(
8  | |     af_flags: AddressFamilyFlags,
9  | |     proto_flags: ProtocolFlags,
10 | | ) -> Result<Vec<SocketInfo>, Error> {
11 | |     iterate_sockets_info(af_flags, proto_flags)?.collect()
   | |     ^^^^^^^^^^^^^^^^^^^^ help: a function with a similar name exists: `get_sockets_info`
12 | | }
   | |_- similarly named function `get_sockets_info` defined here

error: aborting due to previous error

[hanwencheng]

when validation_host is disabled it cause the problem in wasm executor

error[E0412]: cannot find type `ValidationPool` in this scope
  --> parachain/src/wasm_executor/mod.rs:74:13
   |
74 |     Remote(&'a ValidationPool),
   |                ^^^^^^^^^^^^^^ not found in this scope

error[E0412]: cannot find type `ValidationPool` in this scope
  --> parachain/src/wasm_executor/mod.rs:76:17
   |
76 |     RemoteTest(&'a ValidationPool),
   |                    ^^^^^^^^^^^^^^ not found in this scope

[tomaka]

In that file (wasm_executor/mod.rs), try to replace all the
#[cfg(target_os = "unknown")] with #[cfg(any(target_os = "unknown", target_os = "android"))]
and all the
#[cfg(not(target_os = "unknown"))] with #[cfg(not(any(target_os = "unknown", target_os = "android")))]

[hanwencheng]

Thanks, it works!

Does the shared memory only related to the validation process, and that's why we can disable it in Android since the Android node only works as a light client?

[tomaka]

Yes.