rename _res to _result to avoid macro conflict

[lixin-wei]

I met a macro confilict.

It's in resolv.h in linux. In which there is a macro called _res.

So I renamed _res to _result to avoid macro conflict.

[gemini-code-assist]

Summary of Changes

Hello @lixin-wei, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request primarily resolves a build-time macro conflict by consistently renaming an internal variable across the codebase. Additionally, it improves the diagnostic capabilities of the JSON parsing utility by providing more granular error information when parsing operations are unsuccessful.

Highlights

• Macro Conflict Resolution: Renamed the internal variable _res to _result across several files (OneOf.hpp, Variant.hpp, Parser_tagged_union.hpp). This change specifically addresses a macro conflict with _res that occurs in the resolv.h header on Linux systems, preventing build failures.
• Improved JSON Parsing Error Reporting: Enhanced the json::read function to provide more detailed error messages when JSON parsing fails. This was achieved by switching from yyjson_read to yyjson_read_opts and capturing the specific error message provided by the yyjson library.

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[gemini-code-assist]

Code Review

The pull request renames the variable _res to _result to avoid macro conflicts with resolv.h and enhances JSON parsing error reporting by including the error message from yyjson_read_opts. The review suggests improving the error reporting further by including the offset of the error within the JSON string.

[liuzicheng1987]

@lixin-wei thank you for your contribution !

[lixin-wei]

@liuzicheng1987 Just curious, may I ask why you name all variables with a prefix underscore? These names are likely to be used in system headers.

[ZXShady]

I am personally against using _blah variable names as they are ugly and they conflict with macros just drop the _ and they aren't safe to use in the global namespace.