Enable -Werror

[CastilloDel]

Fixes #694

• GCC development requires copyright assignment or the Developer's Certificate of Origin sign-off, see https://gcc.gnu.org/contribute.html or https://gcc.gnu.org/dco.html
• Read contributing guidelines
• make check-rust passes locally
• Run clang-format
• Added any relevant test cases to gcc/testsuite/rust/

The last three ones shouldn't be necessary for this change.

---

Update the CI to use the bootstrap build process and enable -Werror

Signed-off-by: Daniel del Castillo [email protected]

[philberty]

This workflow is used for our normal PR's. So we still want to disable-bootstrap otherwise our PR build/test is going to take way too long. I think all we want to do is --enable-werror or add -Werror to our flags in our rust Makefile

[CastilloDel]

But didn't @/tschwinge said gcc is only supposed to be warning free when using the bootstrap process? I'm talking about this comment. Maybe --enable-werror should be added in bootstrap.yml, then?

[dkm]

Bootstrap is not wanted for every PR (waste of time/resources), and --enable-werror is only meaningful when bootstrap is enabled, if the doc is correct (from your link in the related discussion). So, not really sure this would be useful... ?

[CastilloDel]

I don't really know, I just wanted to fix the issue. But maybe it could be useful in bootstrap.yml which doesn't seem to run as often as ccpp.yml, but does have bootstrap enabled.

[CohenArthur]

@CastilloDel We want to avoid regressions by making sure that our bootstrapped build does not stop working silently at some point. We can do this two ways:

1. by adding -Werror to our build flags in ccpp.yml. We cannot use --enable-werror here as, as you pointed out, it is only enabled when bootstrapping is also enabled. We don't want to bootstrap the compiler every time we create a pull request, as this takes an extremely long time (and our CI already takes something like an hour to run). We can add the -Werror flag in some other way, by specifying CXXFLAGS='-Werror' in the configure and building step for example. I haven't looked into how to do it here but that's typically what you would do.
2. by adding --enable-werror to the bootstrap workflow (bootstrap.yml). This workflow only triggers when changes are pushed to master, so after a PR has been reviewed and approved and merged. This has the disadvantage of not preventing regressions but simply showing that master's build failed when arriving on the repository.

I personally think the first option would be preferable. To show you that you can't use --enable-werror I've added a warning on my clone, by changing feature.c_str() to feature (effectively giving a C++ std::string where a C-equivalent const char * is expected)

../../gcc/rust/rust-session-manager.cc:1011:19: warning: format ‘%s’ expects argument of type ‘char*’, but argument 3 has type ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} [-Wformat=]
 1011 |       rust_debug ("had to implicitly enable feature '%s'!", feature);
      |                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../gcc/rust/rust-diagnostics.h:143:54: note: in definition of macro ‘rust_debug’
  143 | #define rust_debug(...) rust_debug_loc (Location (), __VA_ARGS__)
      |                                                      ^~~~~~~~~~~
../../gcc/rust/rust-session-manager.cc:1011:55: note: format string is defined here
 1011 |       rust_debug ("had to implicitly enable feature '%s'!", feature);
      |                                                      ~^
      |                                                       |
      |                                                       char*

I configured the build directory like so:
./configure --enable-werror --disable-bootstrap --disable-multilib --enable-languages=c,rust
And the build still succeeded, emitting a warning but not treating is as an error. So your solution does not do what you want

[CastilloDel]

I did the first option, but now it doesn't compile :(. Doesn't this have to do with what @/tschwinge said in the issue and I referenced before? I understood that the build process isn't warning free when the bootstrap is disabled.

[CohenArthur]

I'd be fine with the second solution too. The only thing I don't like is that it can fail silently. You can also maybe look into how to add an extra step for our merging bot, bors, so that it runs an extra file before merging to master. This way contributors that open PRs still have reasonably fast feedback where bootstrapping is disabled, but bors performs a full check before merging it to master?

[tschwinge]

I think all that has been said here is correct... ;'-)

I thought I'd seen this suggested somewhere, but now I can't find it anymore: to just enable -Werror for files in gcc/rust/ -- that doesn't work, because these #include generic GCC files, and warning may be coming from those.

---

Just to throw in yet another option (but I'm not convinced that I like it...): bors is running in a mostly stable setup (meaning, here: known GCC version used to build GCC/Rust). We could generate a baseline expected warnings file containing grep 'warning: ' | sort of the build log, to document the baseline set of warning that we get/expect with the GCC version that bors uses to build GCC/Rust. Now, after a successful build, the ongoing bors CI could again do a grep 'warning: ' | sort of the current build log, and diff -U0 that one against the baseline expected warnings file. If that's clean, no new warnings have been introduced, otherwise, report the difference to the user, like a build failure.

That way, we don't get any noticeable overhead for the bors CI runs, and the only downside is that we have to update the baseline expected warnings file if the bors GCC version changes, and when doing merges from GCC upstream. (... which seems reasonable.)

[CohenArthur]

@CastilloDel to debug the CI failure I can recommend the tmate github action! I think in your case it might just be because of the missing newline at the end of the expected_warnings file and an extra libtool warning

[tschwinge]

@CastilloDel, aha, so you're indeed experimenting with my diff suggestion, nice. :-)

I think I convinced myself to "like" it sufficiently. ;-)

[tschwinge]

extra libtool warning

Now that's of course a (solvable) problem if the warnings are not deterministic...

[CastilloDel]

Okay. I read all the comments (you guys have been really helpful!) and now I think I didn't miss anything and it should work.

extra libtool warning

Now that's of course a (solvable) problem if the warnings are not deterministic...

I think that was a human error on my part. The warnings do seem to be deterministic, but you were right that the sort was needed. I didn't realize the build uses concurrency.

Edit:

I suggest to rename the warnings file to log-warnings or similar.

Okay, I missed this. I'll fix it right now

[CohenArthur]

This looks nice! I think it would be better to keep the bors_log_expected_warnings file inside the .github/ directory: When we try to upstream the project, this a directory we're sure to skip, and this file only has a purpose for github actions, meaning it shouldn't get upstreamed either

[CastilloDel]

Done!

[CohenArthur]

LGTM

[tschwinge]

@CastilloDel , I'm looking into this now, thanks!

Still would like to tune a few things, documentation, and try to find a way to make this usable for local "workflows" (standard configure && make, etc.).

Otherwise, I'll now have to route any merges from upstream GCC (#247) through bors/CI. (Which would be fine, too.)

First I've now got some learning to do about https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions, etc. ;-)

I see "Add more commits by pushing to the master branch on CastilloDel/gccrs", so for simplicity, I'll use that branch and this PR #1026 for my work. (Hope you don't mind...) ;-D

[tschwinge]

This step will fail in case that grep doesn't find a single warning. We shall defer that latent problem until relevant... ;-)