CXX-2284 Append platform data to handshake

[kevinAlbs]

Summary

• Prepend compiler ID, compiler version, and C++ standard to the Handshake platform string

Background & Motivation

The Handshake is the first command performed upon establishing the connection to MongoDB.
The Handshake includes metadata in the client field, so a client can identify itself. The Handshake metadata appears in mongod logs.

Here is a formatted log from mongod from a C++ driver connection before this change:

{
    "t": {
        "$date": "2022-12-21T12:02:28.088-05:00"
    },
    "s": "I",
    "c": "NETWORK",
    "id": 51800,
    "ctx": "conn11",
    "msg": "client metadata",
    "attr": {
        "remote": "127.0.0.1:59363",
        "client": "conn11",
        "doc": {
            "driver": {
                "name": "mongoc / mongocxx",
                "version": "1.23.1 / 3.7.1-pre"
            },
            "os": {
                "type": "Darwin",
                "name": "macOS",
                "version": "20.6.0",
                "architecture": "x86_64"
            },
            "platform": "cfg=0x0200d68a65 posix=200112 stdc=201710 CC=clang 13.0.0 (clang-1300.0.29.30) CFLAGS=\"\" LDFLAGS=\"\""
        }
    }
}

The platform only includes information from the C driver. After this change, the platform field includes the C++ compiler ID and version in the prefix:

{
    "t": {
        "$date": "2023-01-03T09:15:05.013-05:00"
    },
    "s": "I",
    "c": "NETWORK",
    "id": 51800,
    "ctx": "conn12",
    "msg": "client metadata",
    "attr": {
        "remote": "127.0.0.1:59806",
        "client": "conn12",
        "doc": {
            "driver": {
                "name": "mongoc / mongocxx",
                "version": "1.23.1 / 3.7.1-pre"
            },
            "os": {
                "type": "Darwin",
                "name": "macOS",
                "version": "20.6.0",
                "architecture": "x86_64"
            },
            "platform": "CXX=AppleClang 13.0.0.13000029 stdcxx=201703 / cfg=0x0200d68a65 posix=200112 stdc=201710 CC=clang 13.0.0 (clang-1300.0.29.30) CFLAGS=\"\" LDFLAGS=\"\""
        }
    }
}

cmake is used to determine the compiler ID and version. The C driver uses macros to determine the compiler ID and version, and falls back to values set by cmake. I see no reason to use macros instead of cmake to determine the compiler type and version for the C++ driver. The C driver may have preferred macros for consistent values between cmake and the now removed autotools build. But I am not sure.

A patch build was run to determine all MONGOCXX_COMPILER_ID and MONGOCXX_COMPILER_VERSION for tested variants. The following table is the unique values:

MONGOCXX_COMPILER_ID	MONGOCXX_COMPILER_VERSION
GNU	8.3.1
AppleClang	11.0.0.11000033
GNU	8.3.0
GNU	9.4.0
GNU	7.5.0
GNU	10.2.1
Clang	6.0.0
GNU	5.4.0
MSVC	19.16.27043.0
MSVC	19.0.24223.0

[codecov-commenter]

Codecov Report

Merging #915 (927ebd3) into master (4b7add4) will decrease coverage by 0.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #915      +/-   ##
==========================================
- Coverage   91.34%   91.28%   -0.06%     
==========================================
  Files         384      384              
  Lines       23463    23312     -151     
==========================================
- Hits        21432    21281     -151     
  Misses       2031     2031              

Impacted Files	Coverage Δ
src/mongocxx/instance.cpp	77.77% <100.00%> (-7.75%)	⬇️
src/mongocxx/test/client.cpp	99.64% <0.00%> (+0.13%)	⬆️

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[vector-of-bool]

LGTM, but with one possible improvement for handling MSVC.

[vector-of-bool]

Possible tweak: The __cplusplus macro is a lie for MSVC (by default). It would be useful to add a field for _MSVC_LANG, which tells the true value of /std: regardless of the compiler conformance options.

[kevinAlbs]

Good point. The installation documentation suggests compiling with /Zc:__cplusplus for C++17. But users may be building with older versions.

Updated to prefer _MSVC_LANG. Filed CXX-2629 to consider setting /Zc:__cplusplus as the default when building with MSVC.