build: make Travis catch unused variables #17486

Sjors · 2019-11-15T09:34:16Z

The two macOS Travis machines run with --enable-werror. This PR adds -Werror=unused-variable to the existing vla, switch and thread-safety-analysis checks. This should prevent the need for fixes like b07b07c, 26a93bc, dd777f3, 99be644, fa39f67, 16bcc1b, bb079a0, bdaed47 and ecf9b25 with minimal nuisance.

Thoughts for followups:

Travis starts these macOS machines fairly late, so we should consider setting --enable-werror on earlier machines as well.
We should encourage the use of --enable-werror by developers. Maybe switch it on by default for --enable-debug?
See practicalswift's overview of other checks to consider in RFC: Enabling some commonly enabled compiler diagnostics #17344

laanwj · 2019-11-15T09:38:31Z

Concept ACK. If we can trust the compiler to be consistent on this.

OTOH this warning was already enabled, and you're only promoting it to -Werror in the CI. I do agree that's the only good use of Werror. It should never be enabled by default by configure scripts. So it should be ok.

practicalswift · 2019-11-15T10:20:18Z

ACK ce47c11

maflcko · 2019-11-15T13:15:03Z

Are you sure this enabled by default? I couldn't find it here: https://clang.llvm.org/docs/DiagnosticsReference.html#wmost

What would be the downside of explicitly enabling it?

maflcko · 2019-11-15T13:16:04Z

Also, would be nice to call git revert on one of the commits and then give us a link to the travis run

Sjors · 2019-11-15T13:33:11Z

Here's a Travis build that should fail: https://travis-ci.org/Sjors/bitcoin/builds/612381391

@MarcoFalke wrote:

Are you sure this enabled by default?

Not sure I understand your question. I tested on my own machine with ./configure --enable-werror and it caught it. We set this for Travis here:

bitcoin/ci/test/00_setup_env_mac_host.sh

Line 16 in 21ee676

export BITCOIN_CONFIG="--enable-gui --enable-reduce-exports --enable-werror"

maflcko · 2019-11-15T13:50:37Z

Oh, I am wondering if -Wunused-variable is enabled by default in clang. Couldn't find it mentioned in the docs.

practicalswift · 2019-11-15T14:02:03Z

@MarcoFalke I think it is enabled by -Wall in GCC, but not in Clang. I incorrectly claimed it being enabled by -Wall also in Clang in #17344. Sorry about that: I've now corrected that comment :)

Sjors · 2019-11-15T14:13:51Z

I normally do get unused variable warnings on macOS.

maflcko · 2019-11-15T14:20:10Z

So to ask my previous question again: What would be the downside of explicitly enabling it instead of relying on clangs undocumented default, which even differs for different oses.

Sjors · 2019-11-15T14:54:14Z

Enabling -Wunused-variable by default sounds good to me, but also orthogonal to this PR, which is about making sure Travis catches it as an error.

laanwj · 2019-11-15T15:10:14Z

I don't think it's entirely orthogonal. If you make a warning an error in the CI, I think it's reasonable to enable it by default (in non-WError mode) for normal builds. Otherwise people will realize it only when the CI fails and with the large turn-around cycle that's suboptimal.

ryanofsky · 2019-11-15T15:19:43Z

If you make a warning an error in the CI, I think it's reasonable to enable it by default (in non-WError mode)

Yes, please. The worst travis problems to deal with are the ones that happen remotely but not locally.

Turn corresponding warning on by default (not always covered by -Wall).

Sjors · 2019-11-15T16:39:57Z

Good point. Added.

New Travis build that should fail: https://travis-ci.org/Sjors/bitcoin/builds/612471016

maflcko · 2019-11-15T17:00:00Z

ACK 18b18f8

practicalswift · 2019-11-15T17:58:26Z

ACK 18b18f8 -- nice!

18b18f8 [build] ./configure --enable-werror: add unused-variable (Sjors Provoost) Pull request description: The two macOS Travis machines run with `--enable-werror`. This PR adds `-Werror=unused-variable` to the existing `vla`, `switch` and `thread-safety-analysis` checks. This should prevent the need for fixes like b07b07c, 26a93bc, dd777f3, 99be644, fa39f67, 16bcc1b, bb079a0, bdaed47 and ecf9b25 with minimal nuisance. Thoughts for followups: * Travis starts these macOS machines fairly late, so we should consider setting `--enable-werror` on earlier machines as well. * We should encourage the use of `--enable-werror` by developers. Maybe switch it on by default for `--enable-debug`? * See practicalswift's overview of other checks to consider in #17344 ACKs for top commit: MarcoFalke: ACK 18b18f8 practicalswift: ACK 18b18f8 -- nice! Tree-SHA512: 892b471ca5ea547f3c952ac88190cbebf8110cb7aec6f20466aeb312aeb0910bfe990f914e153c40ecb55709c03775ef30770412ad76f9d532ca77055596c582

Sjors · 2019-11-15T20:46:16Z

Travis catches the issue as expected (had to restart a few times for timeouts): https://travis-ci.org/Sjors/bitcoin/jobs/612471028#L2333

18b18f8 [build] ./configure --enable-werror: add unused-variable (Sjors Provoost) Pull request description: The two macOS Travis machines run with `--enable-werror`. This PR adds `-Werror=unused-variable` to the existing `vla`, `switch` and `thread-safety-analysis` checks. This should prevent the need for fixes like b07b07c, 26a93bc, dd777f3, 99be644, fa39f67, 16bcc1b, bb079a0, bdaed47 and ecf9b25 with minimal nuisance. Thoughts for followups: * Travis starts these macOS machines fairly late, so we should consider setting `--enable-werror` on earlier machines as well. * We should encourage the use of `--enable-werror` by developers. Maybe switch it on by default for `--enable-debug`? * See practicalswift's overview of other checks to consider in bitcoin#17344 ACKs for top commit: MarcoFalke: ACK 18b18f8 practicalswift: ACK 18b18f8 -- nice! Tree-SHA512: 892b471ca5ea547f3c952ac88190cbebf8110cb7aec6f20466aeb312aeb0910bfe990f914e153c40ecb55709c03775ef30770412ad76f9d532ca77055596c582

This reverts commit 5fe89ff.

Sjors · 2019-11-20T11:56:15Z

This turned out to be premature, reverting the error part in #17533

laanwj · 2019-11-20T12:00:46Z

yup, a textbook example of why to be careful with making things Werror
(didn't see this particular one coming either !)

18b18f8 [build] ./configure --enable-werror: add unused-variable (Sjors Provoost) Pull request description: The two macOS Travis machines run with `--enable-werror`. This PR adds `-Werror=unused-variable` to the existing `vla`, `switch` and `thread-safety-analysis` checks. This should prevent the need for fixes like b07b07c, 26a93bc, dd777f3, 99be644, fa39f67, 16bcc1b, bb079a0, bdaed47 and ecf9b25 with minimal nuisance. Thoughts for followups: * Travis starts these macOS machines fairly late, so we should consider setting `--enable-werror` on earlier machines as well. * We should encourage the use of `--enable-werror` by developers. Maybe switch it on by default for `--enable-debug`? * See practicalswift's overview of other checks to consider in bitcoin#17344 ACKs for top commit: MarcoFalke: ACK 18b18f8 practicalswift: ACK 18b18f8 -- nice! Tree-SHA512: 892b471ca5ea547f3c952ac88190cbebf8110cb7aec6f20466aeb312aeb0910bfe990f914e153c40ecb55709c03775ef30770412ad76f9d532ca77055596c582

This reverts commit 5fe89ff.

merge bitcoin#18914, bitcoin#13306, bitcoin#16424, bitcoin#13899, bitcoin#17486, bitcoin#17880, bitcoin#18145, bitcoin#18843, bitcoin#16710: split warnings out of CXXFLAGS, add more flags

DrahtBot added the Build system label Nov 15, 2019

[build] ./configure --enable-werror: add unused-variable

18b18f8

Turn corresponding warning on by default (not always covered by -Wall).

Sjors force-pushed the 2019/11/Werror-unused-variable branch from ce47c11 to 18b18f8 Compare November 15, 2019 16:37

maflcko merged commit 18b18f8 into bitcoin:master Nov 15, 2019

Sjors deleted the 2019/11/Werror-unused-variable branch November 15, 2019 20:46

sidhujag pushed a commit to syscoin/syscoin that referenced this pull request Nov 16, 2019

Revert "Merge bitcoin#17486: build: make Travis catch unused variables"

53fa6e4

This reverts commit 5fe89ff.

This was referenced Nov 19, 2019

build: Mark depends headers as -isystem #17520

Closed

build: undo Werror=unused-variable #17533

Closed

MarkLTZ mentioned this pull request Apr 4, 2020

Bitcoin PR tracking litecoinz-core/litecoinz#14

Closed

sidhujag pushed a commit to syscoin-core/syscoin that referenced this pull request Nov 10, 2020

Revert "Merge bitcoin#17486: build: make Travis catch unused variables"

921e639

This reverts commit 5fe89ff.

kwvg added a commit to kwvg/dash that referenced this pull request Jun 17, 2021

bitcoin#17486: make Travis catch unused variables

5b52520

kwvg added a commit to kwvg/dash that referenced this pull request Jun 17, 2021

bitcoin#17486: make Travis catch unused variables

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kwvg added a commit to kwvg/dash that referenced this pull request Jun 17, 2021

bitcoin#17486: make Travis catch unused variables

52f3975

bitcoin locked as resolved and limited conversation to collaborators Dec 16, 2021

build: make Travis catch unused variables #17486

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