Docs: Include hint to use `make clean` in build-unix.md

[billygarrison]

Is your feature request related to a problem? Please describe.
When running make while there are other pre-existing builds, there can be errors that don't clearly suggest using make clean. This step may be obvious to experienced developers, but is confusing to many bitcoin users without a background in C/Make. Currently, build-unix.md does not mention using make clean.

Describe the solution you'd like
A simple fix would be to include a hint in the "To build" section of build-unix.md. I'd be happy to make the change myself, but wanted to get feedback first to avoid wasting reviewers' time.

Other changes
build-osx.md also uses make, as does the Windows Subsystem for Linux instructions. Those could be updated with the same note. I'm not familiar with the BSD systems, but the docs say they use gmake, which also appears to have a gmake clean option.

Related issue
#16479

[hebasto]

This step may be obvious to experienced developers, but is confusing to many bitcoin users without a background in C/Make.

Such users run make once only, no?

[billygarrison]

This step may be obvious to experienced developers, but is confusing to many bitcoin users without a background in C/Make.

Such users run make once only, no?

I ran into the issue when upgrading to the latest version. I'm familiar with git but had no idea about make clean.

Steps to upgrade

cd bitcoin
git fetch origin
git reset --hard origin/master
git checkout v0.20.0
./autogen.sh
./configure
make
make install

[hebasto]

@billygarrison

I ran into the issue when upgrading to the latest version. I'm familiar with git but had no idea about make clean.

That makes sense :)

[jonatack]

@billygarrison if helpful to you, I wrote about this here, don't hesitate to look through the article: https://jonatack.github.io/articles/how-to-compile-bitcoin-core-and-run-the-tests. Here's a relevant paragraph:

"On the other hand, when you change the build configuration, and in some cases when testing different PRs, or when the build isn't working, it's often best to start with a clean slate using make clean or make distclean before configuring. Here's a complete example, courtesy of Marco Falke:"

./autogen.sh && ./configure <any BDB flags> && make distclean && ./configure <all flags> && make 

(p.s. git reset --hard origin/master seems unnecessary)

[maflcko]

btw I switched my compile alias to ./autogen.sh && ./configure --enable-c++17 CC=clang CXX=clang++ && make clean && make check, because the double-configure seemed overkill

[hebasto]

FWIW, I have a bunch of aliases:

$ alias
...
alias conf-clang='./autogen.sh && ./configure --with-incompatible-bdb CC=clang-9 CXX=clang++-9 && make clean > /dev/null'
alias conf-clang-debug='./autogen.sh && ./configure --enable-debug --with-incompatible-bdb CC=clang-9 CXX=clang++-9 && make clean > /dev/null'
alias conf-fuzz='./autogen.sh && ./configure --enable-c++17 --enable-fuzz --with-sanitizers=fuzzer,address,undefined CC=clang-9 CXX=clang++-9 && make clean > /dev/null'
alias conf-gcc='./autogen.sh && ./configure --with-incompatible-bdb && make clean > /dev/null'
alias conf-gcc-17='./autogen.sh && ./configure --with-incompatible-bdb --enable-c++17 && make clean > /dev/null'
alias conf-gcc-debug='./autogen.sh && ./configure --enable-debug --with-incompatible-bdb && make clean > /dev/null'
...

😃

[jonatack]

btw I switched my compile alias to ./autogen.sh && ./configure --enable-c++17 CC=clang CXX=clang++ && make clean && make check, because the double-configure seemed overkill

Thanks @MarcoFalke, will update. I was wondering if the benefit of double configuring was worth it.

---

@hebasto interesting, thanks, I have a bunch too at https://github.com/jonatack/dotfiles/blob/master/bash_aliases#L331 which has turned a bit into flag soup :D ... always interesting to see what others are doing to keep sharpening the tools.

(Edit for casual observers: Don't use these bash aliases for building to run a node in production! They are for testing and debugging purposes and the builds with them run much more slowly.)

[maflcko]

Another one to run a command on the commits of a branch: (I think already mentioned in productivity.md)

$ which tbc  # test bitcoin core
tbc ()
{ 
    git rebase --interactive --exec "make check -j 9 && ./test/functional/test_runner.py -j 9" $(git merge-base bitcoin-core/master HEAD)
}

Edit: :) https://github.com/bitcoin/bitcoin/blob/master/doc/productivity.md#interactive-dummy-rebases-for-fixups-and-execs-with-git-merge-base

[fanquake]

Going to close this for now. I don't think we need to add/maintain basic make usage notes in our build documentation.