cling: 0.9 -> 1.0

[thomasjm]

Description of changes

Working on Cling 1.0, per the advice of @vgvassilev on #283989.

This currently builds, but has some path troubles. Marking as draft for now.

CC @a-n-n-a-l-e-e , @wegank

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

[thomasjm]

Okay, this seems to be working now. Ready for review!

[RossComputerGuy]

$ ./result/bin/cling
In file included from input_line_1:1:
/nix/store/8y16aj4mk0rbck2hlg538322d5r1gi7m-gcc-13.2.0/include/c++/13.2.0/new:40:10: fatal error: 'bits/c++config.h' file not found
#include <bits/c++config.h>
         ^~~~~~~~~~~~~~~~~~
Warning in cling::IncrementalParser::CheckABICompatibility():
  Failed to extract C++ standard library version.
Replaced symbol atexit cannot be found in JIT!
Replaced symbol at_quick_exit cannot be found in JIT!

****************** CLING ******************
* Type C++ code and press enter to run it *
*             Type .q to exit             *
*******************************************
[cling]$

Builds fine on my M1 Pro under NixOS, but these errors are concerning. Though I don't know anything about cling but these errors still concern me.

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/prs-ready-for-review/1016/122

[wegank]

Suggested change

	"-l" "${llvmPackages_13.libcxx}/lib/libc++.so"
	"-l" "${llvmPackages_13.libcxx}/lib/libc++${stdenv.hostPlatform.extensions.sharedLibrary}"

[wegank]

$ ./result/bin/cling
In file included from input_line_1:1:
/nix/store/8y16aj4mk0rbck2hlg538322d5r1gi7m-gcc-13.2.0/include/c++/13.2.0/new:40:10: fatal error: 'bits/c++config.h' file not found
#include <bits/c++config.h>
         ^~~~~~~~~~~~~~~~~~
Warning in cling::IncrementalParser::CheckABICompatibility():
  Failed to extract C++ standard library version.
Replaced symbol atexit cannot be found in JIT!
Replaced symbol at_quick_exit cannot be found in JIT!

****************** CLING ******************
* Type C++ code and press enter to run it *
*             Type .q to exit             *
*******************************************
[cling]$

Builds fine on my M1 Pro under NixOS, but these errors are concerning. Though I don't know anything about cling but these errors still concern me.

Looks like enabling useLLVMLibcxx on darwin should fix the issue? Something GCC-related is always strange on darwin.

[RossComputerGuy]

enabling useLLVMLibcxx on darwin

The problem is I am not under Darwin but under NixOS on Apple Silicon.

[wegank]

Oh, that's not nice at all. But maybe enabling useLLVMLibcxx will still help?

[RossComputerGuy]

Well, I get even more interesting errors with that option enabled:

$ ./result/bin/cling
Warning in cling::IncrementalParser::CheckABICompatibility():
  Failed to extract C++ standard library version.
In file included from input_line_3:1:
/nix/store/nrqmhzgg3wfnqf2qrqdrl6mbss3lfp9w-libcxx-13.0.1/lib/libc++.so:1:1: error: C++ requires a type specifier for all declarations
INPUT(libc++.so.1 -lc++abi)
^
/nix/store/nrqmhzgg3wfnqf2qrqdrl6mbss3lfp9w-libcxx-13.0.1/lib/libc++.so:1:7: error: use of undeclared identifier 'libc'
INPUT(libc++.so.1 -lc++abi)
      ^
/nix/store/nrqmhzgg3wfnqf2qrqdrl6mbss3lfp9w-libcxx-13.0.1/lib/libc++.so:1:28: error: expected ';' after top level declarator
INPUT(libc++.so.1 -lc++abi)
                           ^
                           ;

****************** CLING ******************
* Type C++ code and press enter to run it *
*             Type .q to exit             *
*******************************************
[cling]$

[wegank]

So useLLVMLibcxx doesn't look so good on Linux.

What if we replaced x86_64-unknown-linux-gnu with ${stdenv.hostPlatform.config} in the expression, while keeping useLLVMLibcxx disabled on Linux?

[RossComputerGuy]

So useLLVMLibcxx doesn't look so good on Linux.

At least on aarch64-linux, no it's not good at all.

What if we replaced x86_64-unknown-linux-gnu with ${stdenv.hostPlatform.config} in the expression, while keeping useLLVMLibcxx disabled on Linux?

Amazing, it works.

$ ./result/bin/cling

****************** CLING ******************
* Type C++ code and press enter to run it *
*             Type .q to exit             *
*******************************************
[cling]$

[wegank]

Thanks! Both changes should also be needed in 0.9, so I assume they are not regressions of this PR. I'll create a follow-up PR for that.