I seem to be having a similar issue on my system. I am working on a C++ project and the extension does not seem to be handling C++ syntax properly, as people have mentioned above in this issue. I have been manually reverting the C++ extension back to version 0.24.1, as that seems to be the most recent extension version where the problem does not occur.

I ran the C/C++: Log Diagnostics command on both versions of the extension, and I've noticed that the Standard Version is different for the same translation unit. I have redacted some project-specific information (includes, source file names) from the output, as it may be confidential and I don't feel comfortable sharing it.

-------- Diagnostics - 11/18/2019, 12:40:23 PM
Version: 0.26.1
Current Configuration:
{
    "name": "Linux",
    "includePath": [
        "${workspaceFolder}/src/include",
        "${workspaceFolder}/src",
        "/usr/include/x86_64-linux-gnu/c++/7",
        "/usr/include/c++/7"
    ],
    "defines": [],
    "compilerPath": "/usr/bin/gcc",
    "cStandard": "c11",
    "cppStandard": "c++11",
    "intelliSenseMode": "${default}",
    "compilerArgs": []
}
Translation Unit Mappings:
[ <REDACTED>.C ]:
    <REDACTED>.H
Translation Unit Configurations:
[ <REDACTED>.C ]:
    Process ID: 834
    Memory Usage: 29 MB
    Compiler Path: /usr/bin/gcc
    Includes:
        <REDACTED - workspace include path>
        <REDACTED - workspace include path>
        /usr/include/x86_64-linux-gnu/c++/7
        /usr/include/c++/7
        /usr/lib/gcc/x86_64-linux-gnu/7/include
        /usr/local/include
        /usr/lib/gcc/x86_64-linux-gnu/7/include-fixed
        /usr/include/x86_64-linux-gnu
        /usr/include
        <REDACTED - translation unit-specific include path>
    Standard Version: c11
    IntelliSense Mode: gcc-x64
    Other Flags:
        --gcc
        --gnu_version=70400
Total Memory Usage: 29 MB

The output for version 0.24.1 is almost identical, but the Standard Version is c++11 instead of c11. Is it possible that the 0.26.1 version of the extension is treating the C++ source files as C source files instead? I thought that might explain why it seems C++ specific syntax is not being handled properly. Our naming conventions for our C++ source and header files are somewhat abnormal (.C/.H), but it doesn't seem like this was a problem in earlier versions of the extension. I have the language mode set to C++ for these filename extensions, and I've verified that the language mode setting for this specific translation unit is C++ (not sure if that makes a difference)

Originally posted by @bwarrum-ibm in #4614 (comment)