Add the [[nodiscard]] attribute to the result class

[indiosmo]

No description provided.

[zajo]

The difficulty with these failures is that with LEAF being a standalone library, it doesn't use Boost Config. We need the correct compiler-specific ifdefs in leaf/config.hpp.

[indiosmo]

Not sure I understand, the macro in question is already defined in leaf/config.hpp, line 212.

  #if defined(__has_attribute) && defined(__SUNPRO_CC) && (__SUNPRO_CC > 0x5130)
  #   if __has_attribute(nodiscard)
  #       define BOOST_LEAF_ATTRIBUTE_NODISCARD [[nodiscard]]
  #   endif
  #elif defined(__has_cpp_attribute)
      //clang-6 accepts [[nodiscard]] with -std=c++14, but warns about it -pedantic
  #   if __has_cpp_attribute(nodiscard) && !(defined(__clang__) && (__cplusplus < 201703L)) && !(defined(__GNUC__) && (__cplusplus < 201100))
  #       define BOOST_LEAF_ATTRIBUTE_NODISCARD [[nodiscard]]
  #   endif
  #endif
  #ifndef BOOST_LEAF_ATTRIBUTE_NODISCARD
  #   define BOOST_LEAF_ATTRIBUTE_NODISCARD
  #endif

• edit1
  Perhaps you mean this is not sufficient, and boost config handles the missing cases, is that it?

• edit2
  I'm looking into Boost Config and the only mention of [[nodiscard]] is in detail/suffix.hpp, and it's exactly the same macro definition that is in leaf/config.hpp so I'm not sure how Boost Config would help here.

[zajo]

I mean the ifdefs are not correct, we need to inspect the error logs to see what's the problem. The goal is to make leaf/config.hpp behave the same as boost/config.hpp (which I presume is correct) in terms of detecting the relevant [nodiscard] support in various compiler versions. I might be able look into it during the weekend.

[indiosmo]

I looked into boost/config.hpp and it seems to be exactly the same as leaf/config.hpp as far as [[nodiscard]] is concerned.

Also, I tried looking at the CI logs but all the ones that failed are blank after line 49.

[zajo]

The logs don't end at line 49, it just takes a while for github to fetch the whole thing. The logs are tens of thousands of lines long, that's why. :)

[indiosmo]

I've reverted the changes to see if all tests pass, as at a cursory look it seems that some of the errors are unrelated to the change. Let's see.

edit:
Nevermind, here's a failure for nodiscard specifically:

2024-05-10T16:59:48.1125656Z In file included from ./boost/leaf/result.hpp:9:0,
2024-05-10T16:59:48.1128442Z from libs/leaf/test/_hpp_result_test.cpp:6:
2024-05-10T16:59:48.1129879Z ./boost/leaf/config.hpp:219:47: error: expected identifier before '[' token
2024-05-10T16:59:48.1131442Z # define BOOST_LEAF_ATTRIBUTE_NODISCARD [[nodiscard]]

[zajo]

Yes, the issue is in the nodiscard macro.