Add seastar 2211 version to infra

[travisdowns]

The existing seastar version 1808 is more than five years old and lots of exciting changes have occurred since then. This patch adds seastar 2211 from last last year so that it can be be exposed by CE.

[mattgodbolt]

Thanks Travis!

[mattgodbolt]

There's no trunk install, but I'll hack that now.

[mattgodbolt]

Oh...there is...sorry! 😊

[travisdowns]

Thanks so much for merging this @mattgodbolt - we are having a lot of fun with it already!

A couple of questions came up while we making this PR, I guess either you or @partouf would know:

• Is there a way to declare that the use of on library in CE requires another? E.g., sesatar needs fmt, so that when you select fmt in the UI, fmt would also be enabled (guessing no, but thought I'd check). I see a "dependencies" concept but I think it's for link time?
• Seastar headers requires a default define to compile at all, like -DSEASTAR_SCHEDULING_GROUPS=16. I just add it to the compiler command line manually, but is there any way to specify this in the CE properties so it happens automatically?

[partouf]

Dependencies are mostly for linking yes, dependencies are hard because you would have to pre-define the version of the library, where we'd like to keep some flexibility.

There are however some libraries that add the include paths of specific versions to their own, so it's automatic, but also hardcoded. (example https://github.com/compiler-explorer/compiler-explorer/blob/4a8fdbf81005517e9b77242856d2651d20438145/etc/config/c%2B%2B.amazon.properties#L3822)

What we usually do is just add something to the description of the library (example https://github.com/compiler-explorer/compiler-explorer/blob/main/etc/config/c%2B%2B.amazon.properties#L3186)

Regarding the define: QT needed that too, we solved it with this https://github.com/compiler-explorer/compiler-explorer/blob/4a8fdbf81005517e9b77242856d2651d20438145/etc/config/c%2B%2B.amazon.properties#L3979 - note that you will not be able to override this define.

[Genomorf]

Thank you for adding the new seastar version to CE. Happy to see it.
@travisdowns could you please help me to figure out how to use it? I can't run simple Hello World application in CE. I guess i miss some crucial command line arguments. Link: https://godbolt.org/z/nx1K5E7b1

My setup is clang 16.0, args are: -std=c++20 -O3 -DSEASTAR_SCHEDULING_GROUPS_COUNT=16. It compiles but i get linker error: undefined reference to `seastar::app_template::app_template(seastar::app_template::config)'. Looks like CE is unable to find definition of the function. How to fix it? Do i need to pass some args to a linker?

[travisdowns]

@Genomorf here's a working link:

https://gcc.godbolt.org/z/WjG3aoY64

Keys are:

Define SEASTAR_SCHEDULING_GROUPS_COUNT either before header include or with -D on the command line.
Include boost and fmt libraries. Currently trunk version works for those.
Use -std=c++17 or 20, or for trunk, 23.

[Genomorf]

@travisdowns thank you for the answer, but your example has the same linker error. If you open the "output" tab you can see undefined reference to `seastar::yield()' error.

I use CE as a sandbox platform to run the code, print messages, experiment with the tasks. I can't do it with your example. It only compiles.

Is there an option to actually run the code?

[partouf]

We do not build binaries for seastar, so linking will not work.

We can look into it

[partouf]

#1415

[Genomorf]

@partouf is it hard for CE to build binaries for seastar? I can help and try to solve the issue if there is a guide or example, or at least some directions how to do it.