Tim Ruffing

Concept ACK

Hm, thanks. It's a bit mysterious that this happens only with `-flto` and only when compiling tests or noverify_tests, but for example not in the exhaustive_tests. But okay, whatever, apparently...

cc @hebasto , any further ideas here?

> The [`-flto-partition=1to1`](https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-flto-partition) option helps: Hm, interesting and good to know. I guess, we should still make sure the build is clean with just `-lto`. Any suggestions here?

Reported to GCC: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116478

> The `enable_testing()` command invocation is required for `add_test()` commands, which are used only for `{noverify_}tests`, `exhaustive_tests` and examples. I don't think it's required. It's just that `add_test()` has no...

I think we want to check for undefined symbols, and `-Wl,--no-undefined` seems to be the canonical way of doing so. I assume one important exception is builds with external default...

> When running `make -j… check` I noticed it doesn't use more than 3 CPU's at any one time, one for `tests`, `exhaustive_tests` and `noverify_tests`. At least when I tried...

> (or maybe we could be a little bit smart and divide 64 by the `-j` value I checked, and I don't think there's no way to access the `-j`...

Good observations. These should be fixed if the rule is as in this comment: ``` # Print tools' flags on best-effort. Include the abstracted # CMake flags that we touch...