223b1ba7d90509a47ea07af46f4b9c3b8efbc9f8 doc: Use CONFIG_SITE instead of --prefix (Hennadii Stepanov)
Pull request description:
The current examples of `--prefix=...` option usage to point `configure` script to appropriate `depends` directory is not [standard](https://www.gnu.org/prep/standards/html_node/Directory-Variables.html). This causes some [confusion](https://github.com/bitcoin/bitcoin/pull/16691) and a bit of inconvenience.
Consider a CentOS 7 32 bit system. Packages `libdb4-devel`, `libdb4-cxx-devel`, `miniupnpc-devel` and `zeromq-devel` are unavailable from repos. After recommended build with depends:
```
cd depends
make
cd ..
./autogen.sh
./configure --prefix=$PWD/depends/i686-pc-linux-gnu
make
```
a user is unable to `make install` compiled binaries neither locally (to `~/.local`) nor system-wide (to `/usr/local`) as `--prefix` is set already.
Meanwhile, the standard approach with using [`config.site`](https://www.gnu.org/software/automake/manual/html_node/config_002esite.html) files allows both possibilities:
```
cd depends
make
cd ..
./autogen.sh
CONFIG_SITE=$PWD/depends/i686-pc-linux-gnu/share/config.site ./configure --prefix ~/.local
make
make install
```
or
```
CONFIG_SITE=$PWD/depends/i686-pc-linux-gnu/share/config.site ./configure
make
sudo make install # install to /usr/local
```
Moreover, this approach is used in [Gitian descriptors](https://github.com/bitcoin/bitcoin/tree/master/contrib/gitian-descriptors) already.
ACKs for top commit:
practicalswift:
ACK 223b1ba7d90509a47ea07af46f4b9c3b8efbc9f8: patch looks correct
fanquake:
ACK 223b1ba7d90509a47ea07af46f4b9c3b8efbc9f8
Tree-SHA512: 46d97924f0fc7e95ee4566737cf7c2ae805ca500e5c49af9aa99ecc3acede4b00329bc727a110aa1b62618dfbf5d1ca2234e736f16fbdf96d6ece5f821712f54
e2bab2aa162ae38b2bf8195b577c982402fbee9d multiprocess: add multiprocess travis configuration (Russell Yanofsky)
603fd6a2e708c04ef6c9880f89d0a4cbaa6fc7c5 depends: add MULTIPROCESS depends option (Russell Yanofsky)
5d1377b52bfcd4edf8553aaf332bfeb92fc554cc build: multiprocess autotools changes (Russell Yanofsky)
Pull request description:
This PR is part of the [process separation project](https://github.com/bitcoin/bitcoin/projects/10).
---
This PR consists of build changes only. It adds an `--enable-multiprocess` autoconf option (off by default and marked experimental), that builds new `bitcoin-node` and `bitcoin-gui` binaries. These currently function the same as existing `bitcoind` and `bitcoin-qt` binaries, but are extended in #10102 with IPC features to execute node, wallet, and gui functions in separate processes.
In addition to adding the `--enable-multiprocess` config flag, it also adds a depends package and autoconf rules to build with the [libmultiprocess](https://github.com/chaincodelabs/libmultiprocess) library, and it adds new travis configuration to exercise the build code and run functional tests with the new binaries.
The changes in this PR were originally part of #10102 but were moved into #16367 to be able to develop and review the multiprocess build changes independently of the code changes. #16367 was briefly merged and then reverted in #18588. Only change since #16367 has been dropping the `native_boost.mk` depends package which was pointed out to be no longer necessary in https://github.com/bitcoin/bitcoin/pull/16367#issuecomment-596484337 and https://github.com/bitcoin/bitcoin/pull/18588#pullrequestreview-391765649
ACKs for top commit:
practicalswift:
ACK e2bab2aa162ae38b2bf8195b577c982402fbee9d
Sjors:
tACK e2bab2aa162ae38b2bf8195b577c982402fbee9d on macOS 10.15.4
hebasto:
ACK e2bab2aa162ae38b2bf8195b577c982402fbee9d, tested on Linux Mint 19.3 (x86_64):
Tree-SHA512: b5a76eab5abf63d9d8b6d628cbdff4cc1888eef15cafa0a5d56369e2f9d02595fed623f4b74b2cf2830c42c05a774f0943e700f9c768a82d9d348cad199e135c
