Expose cc-rs no_default_flags for hassle-free cross-compilation

[ivmarkov]

In our own instantiation of cmake-rs Config, we would like to suppress the cc-rs logic that generates GCC flags based on Rust target triple analysis. Two reasons for that:

• The current logic in cc-rs is not really working well for (at least some?) RISCV targets
• We anyway have all the necessary flags, and we would like to pass those as-is - no more - no less flags, so there is no real need for the cc-rs crate to help us in that

[ivmarkov]

@tgross35 I'm so sorry for pinging you every now and then (last time in the libc crate). :(

Due to recent hurdles with the cc-rs crate when cross-compiling ESP-IDF, we need this enhancement relatively urgently.

Do you think you could spend a few minutes reviewing it? Hopefully, the change is small enough and would actually benefit everybody, who is in a cross-compiling use case.

[ivmarkov]

@tgross35 ? Anybody? This is stopping us from releasing the esp-idf-* crates and the change is really only 3 lines.

[NobodyXu]

Not a maintainer, but just my two nits, I think it makes more sense if the no_default_flags override the ndk

[ivmarkov]

Not a maintainer, but just my two nits, I think it makes more sense if the no_default_flags override the ndk

This would break backwards compatibility when building for Android.
I would not do that.

[NobodyXu]

Thanks that makes it clear.

I will try get back to the upstream issue when I have time.

[ivmarkov]

Not a maintainer, but just my two nits, I think it makes more sense if the no_default_flags override the ndk

This would break backwards compatibility when building for Android. I would not do that.

Hm. Now that I looked more carefully in your changes, you are not doing "if the no_default_flags override the ndk"?
You just replaced "A || B" with "B || A". What's the point?
Am I missing something?

[NobodyXu]

You just replaced "A || B" with "B || A". What's the point?

Well I think if user explicitly ask to disable using default flag from cc-rs, then cmake should always obey their demand and turn it off.

[ivmarkov]

You just replaced "A || B" with "B || A". What's the point?

Well I think if user explicitly ask to disable using default flag from cc-rs, then cmake should always obey their demand and turn it off.

1- But my change does exactly that. Please review carefully again and tell me how it is not doing that?
Note that the previous behavior of cmake-rs was that if the Android NDK is detected, then cmake-rs forcefully enables the "no_default_flags" of cc-rs. I just kept this behavior and added "also enable no_default_flags for cc-rs if the user asked explicitly for that".

2- Look at your suggested change:

My change: .no_default_flags(ndk || self.no_default_flags);
Your suggestion: .no_default_flags(self.no_default_flags || ndk);

How is your suggestion different from what I'm already implementing in this PR?

[NobodyXu]

Oh you are right, sorry my brain must have stopped working

[SergioGasquez]

Can we get some feedback on these changes? (sorry for pinging again)

[NobodyXu]

Maybe you could ask on zulip?

I could try pinging for you

[SergioGasquez]

I could try pinging for you

I'd appreciate it a lot since I dont use Zulip. Thanks for your help!

[thomcc]

This seems reasonable to me.