meson: make backtrace dependency on execinfo

[neheb]

musl libc for example has no such header.

Signed-off-by: Rosen Penev rosenp@gmail.com

[terrelln]

This could enable backtraces when use_backtrace is false. Otherwise it looks good to me.

[eli-schwartz]

use_backtrace cannot be false anymore, it was changed away from a boolean.

It's now a feature option with the default value of "disabled" which means that when used in the required: kwarg, it logs that it is skipping the check "because feature backtrace is disabled".

[terrelln]

@eli-schwartz Thanks for the info! I checked out the source code and it looks like you're correct.

I previously looked at the documentation for has_header(), and I saw that:

required: If set to true, Meson will halt if the header check fails.

This seems to me that if required = disabled then execinfo.found() could still return true. So it seems the documentation is out of date. Likely it wasn't updated when required was changed to accept a feature.

[terrelln]

Thanks for the PR!

[eli-schwartz]

So it seems the documentation is out of date. Likely it wasn't updated when required was changed to accept a feature.

Actually, it's not described anywhere else it is accepted either.

I've reworded the docs slightly, a new version of the website is in progress.