build: Drop boost-system dependency #21066

There no reasons why the libboost-system-dev package could be required.

Concept ACK. I had been thinking about splitting this out of #20744.

Does this work with Boost < 1.65.0?

You'll also need to drop $BOOST_SYSTEM_LIB from BOOST_LIBS in configure.ac.

Actually, I looked at this too quickly. This doesn't modify/remove any of the boost::system::error_code ec; usage in our code?

@fanquake

Actually, I looked at this too quickly. This doesn't modify/remove any of the boost::system::error_code ec; usage in our code?

$ git grep -n -e 'boost::system::error_code'
src/wallet/db.cpp:17:    boost::system::error_code ec;
src/wallet/db.cpp:81:    boost::system::error_code ec;
src/wallet/db.cpp:105:    boost::system::error_code ec;
src/wallet/load.cpp:23:        boost::system::error_code error

Interesting, why I have no errors during compiling and cross-compiling with depends?

Interesting, why I have no errors during compiling and cross-compiling with depends?

If you try and build using Boost < 1.69.0, it will fail to link (1f65eac0b809ca4441cfaa6c9da4b9d3e47581d3):

make[2]: Leaving directory '/bitcoin'
  CXXLD    bitcoind
/usr/bin/ld: bitcoind-bitcoind.o: undefined reference to symbol '_ZN5boost6system15system_categoryEv'
//usr/lib/x86_64-linux-gnu/libboost_system.so.1.62.0: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
Makefile:4980: recipe for target 'bitcoind' failed
make[1]: *** [bitcoind] Error 1

  AR       libbitcoin_wallet.a
  CXXLD    bitcoind
/usr/bin/ld: bitcoind-bitcoind.o: undefined reference to symbol '_ZN5boost6system15system_categoryEv'
//usr/lib/x86_64-linux-gnu/libboost_system.so.1.65.1: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
Makefile:4980: recipe for target 'bitcoind' failed
make[1]: *** [bitcoind] Error 1

See the Boost System revision history:

Boost 1.69.0 Boost.System is now header-only. A stub library is still built for compatibility, but linking to it is no longer necessary.

$ git grep -n -e 'boost::system::error_code'

Right-I don't think getting rid of boost::system makes sense before boost::filesystem. The error codes from boost::system are used internally all over the place.

Closing in favor of #20744.

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #21064 (refactor: use std::shared_mutex & remove Boost Thread by fanquake)
• #20744 ([POC] Use std::filesystem. Remove Boost Filesystem & System by fanquake)
• #16546 (External signer support - Wallet Box edition by Sjors)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.