Duplicate system include path in user config not being auto-removed

[vincentmathis]

Describe the bug

• OS and Version: Windows 7 64bit
• VS Code Version: 1.24.1
• C/C++ Extension Version: Should be the newest.

IntelliSense didn't find stdlib.h in C:/MinGW/include
Other headers in this path were no problem though.

I changed the path to C:\MinGW\include and now it finds stdlib.h
Using forward slashes worked fine a few days ago.

{
    "configurations": [
        {
            "name": "Windows",
            "browse": {
                "path": [
                    "${workspaceFolder}",
                    "${workspaceFolder}\\include",
                    "C:\\MinGW\\include"
                ],
                "limitSymbolsToIncludedHeaders": true
            },
            "includePath": [
                "${workspaceFolder}",
                "${workspaceFolder}\\include",
                "C:\\MinGW\\include"
            ],
            "defines": [],
            "compilerPath": "C:\\MinGW\\bin\\g++.exe",
            "cppStandard": "c++17",
            "intelliSenseMode": "clang-x64",
            "cStandard": "c89"
        }
    ],
    "version": 4
}

Changing it to

 "includePath": [
                "${workspaceFolder}",
                "${workspaceFolder}\\include",
                "C:/MinGW/include"
            ],

shows cannot open source file "stdlib.h" (dependency of "string")
Other header in this path like C:/MinGW/include/SDL2/SDL.h don't produce this error.

[bobbrow]

The bug is that our duplicate path removal logic is failing to remove your c:/MinGW/include path. The system include path requires very specific ordering for GCC/CLang because of the use of #include_next so when you provide the compilerPath we attempt to remove any duplicates so that your config does not accidentally disrupt the ordering.

This is a bug we should fix, but fortunately, you can fix your problem right now by just deleting the c:/MinGW/include line from your configuration. We're already using that path internally.

[sean-mcmanus]

This should be fixed with the latest insiders: https://github.com/Microsoft/vscode-cpptools/releases (unless the includePath ends with "/").