Compiler query should handle GCC-like compilers that support C but not C++ (i.e. Microchip's XC16)

[ReimuNotMoe]

Bug type: Language Service

Describe the bug

• OS and Version: Debian GNU/Linux 10 (buster)
• VS Code Version: 1.56.1
• C/C++ Extension Version: 1.3.1
• Other extensions you installed (and if the issue persists after disabling them): CMake Tools 1.7.3
• If using SSH remote, specify OS of remote machine: none

System include path can't be pulled from Microchip's XC16 compiler.

I have a PIC24 MCU project which uses CMake and worked well in CLion.

When I open the project in VSCode, it can be correctly built by clicking on the Build button. However, all #include <xc.h> lines are red underlined.

The compiler path is already set in CMakeLists.txt. I tried to mess with compilerPath and includePath in c_cpp_properties.json, and none of them worked.

The XC16 is a modified GCC and its usages are exactly same as GCC.

Steps to reproduce

1. Change compilerPath in c_cpp_properties.json to /opt/microchip/xc16/v1.70/bin/xc16-gcc
2. Nothing changed. All #include <xc.h> lines are still red underlined.
3. Add /opt/microchip/xc16/v1.70/support/** (which contains the xc.h file) to includePath in c_cpp_properties.json
4. Nothing changed as well. All #include <xc.h> lines are still red underlined.
5. Run C/C++: Log Diagnostics, and there are no lines begin with /opt/microchip/xc16/v1.70/support/.

Expected behavior
There shouldn't be any red underlines in code.

Code sample and logs

• Code sample

#include <xc.h>

int main(){
  while (1) {
    LATFbits.LATF1 = !LATFbits.LATF1; // Blink a LED
  }
}

• CMakeLists part of setting the compiler

if (XC16_TARGET_CPU)
    message("-- FindXC16: CPU set to ${XC16_TARGET_CPU}")
    set(XC16_COMPILER_OPTIONS -mcpu=${XC16_TARGET_CPU})

    if (NOT XC16_DISABLE_DEFAULT_LINKER_SCRIPT)
        message("-- FindXC16: Using default linker script for device ${XC16_TARGET_CPU}")
        set(XC16_LINKER_OPTIONS --script=p${XC16_TARGET_CPU}.gld)
    else()
        message("-- FindXC16: Default linker script disabled")
    endif()
endif()

if (UNIX)
    if (APPLE)
        set(XC16_DEFAULT_SEARCH_PATH /Applications/microchip/xc16/)
    else()
        set(XC16_DEFAULT_SEARCH_PATH /opt/microchip/xc16/)
    endif()
endif()

if (WIN32)
    set(XC16_DEFAULT_SEARCH_PATH "D:/Microchip/xc16/")
endif()

if (NOT XC16_SEARCH_PATH)
    message("-- FindXC16: Variable XC16_SEARCH_PATH isn't defined, default to ${XC16_DEFAULT_SEARCH_PATH}")
    set(XC16_SEARCH_PATH ${XC16_DEFAULT_SEARCH_PATH})
endif()

set(CMAKE_C_LINK_FLAGS "")

file(GLOB_RECURSE XC16_C_COMPILER ${XC16_SEARCH_PATH}/xc16-gcc)
if (XC16_C_COMPILER)
    message("-- FindXC16: Found xc16-gcc at ${XC16_C_COMPILER}")
    set(CMAKE_C_COMPILER    ${XC16_C_COMPILER})
    set(CMAKE_ASM_COMPILER  ${XC16_C_COMPILER})
endif()

file(GLOB_RECURSE XC16_CXX_COMPILER ${XC16_SEARCH_PATH}/xc16-g++)
if (XC16_CXX_COMPILER)
    message("-- FindXC16: Found xc16-g++ at ${XC16_CXX_COMPILER}")
    set(CMAKE_CXX_COMPILER ${XC16_CXX_COMPILER})
else()
    message("-- FindXC16: xc16-g++ not found, C++ support disabled")
endif()

file(GLOB_RECURSE XC16_AR ${XC16_SEARCH_PATH}/xc16-ar)
if (XC16_AR)
    message("-- FindXC16: Found xc16-ar at ${XC16_AR}")
    set(CMAKE_AR ${XC16_AR})
endif()

file(GLOB_RECURSE XC16_OBJCOPY ${XC16_SEARCH_PATH}/xc16-objcopy)
if (XC16_OBJCOPY)
    message("-- FindXC16: Found xc16-objcopy at ${XC16_OBJCOPY}")
    set(CMAKE_OBJCOPY ${XC16_OBJCOPY})
endif()

file(GLOB_RECURSE XC16_OBJDUMP ${XC16_SEARCH_PATH}/xc16-objdump)
if (XC16_OBJDUMP)
    message("-- FindXC16: Found xc16-objdump at ${XC16_OBJDUMP}")
    set(CMAKE_OBJDUMP ${XC16_OBJDUMP})
endif()

file(GLOB_RECURSE XC16_BIN2HEX ${XC16_SEARCH_PATH}/xc16-bin2hex)
if (XC16_BIN2HEX)
    message("-- FindXC16: Found xc16-bin2hex at ${XC16_BIN2HEX}")
    set(CMAKE_OBJDUMP ${XC16_BIN2HEX})
endif()

add_compile_options(${XC16_COMPILER_OPTIONS} -Wcast-align -omf=elf -DXPRJ_default=default -legacy-libc -msmart-io=1 -msfr-warn=off)

add_link_options(-Wl,--defsym=__MPLAB_BUILD=1,${XC16_LINKER_OPTIONS},--stack=16,--check-sections,--data-init,--pack-data,--handles,--isr,--no-gc-sections,--fill-upper=0,--stackguard=16,--no-force-link,--smart-io,--report-mem)

• CMake output

[variant] Loaded new set of variants
[kit] Successfully loaded 8 kits from /root/.local/share/CMakeTools/cmake-tools-kits.json
[main] Configuring folder: PICo24_SDK 
[cmake] -- FindXC16: Variable XC16_SEARCH_PATH isn't defined, default to /opt/microchip/xc16/
[cmake] -- FindXC16: Found xc16-gcc at /opt/microchip/xc16//v1.70/bin/xc16-gcc
[cmake] -- FindXC16: Found xc16-g++ at /opt/microchip/xc16//v1.70/bin/xc16-g++
[cmake] -- FindXC16: Found xc16-ar at /opt/microchip/xc16//v1.70/bin/xc16-ar
[cmake] -- FindXC16: Found xc16-objcopy at /opt/microchip/xc16//v1.70/bin/xc16-objcopy
[cmake] -- FindXC16: Found xc16-objdump at /opt/microchip/xc16//v1.70/bin/xc16-objdump
[cmake] -- FindXC16: Found xc16-bin2hex at /opt/microchip/xc16//v1.70/bin/xc16-bin2hex
[cmake] -- PICo24: Using board: PotatoPi_PICo24, CPU: 24FJ256GB206
[cmake] Configuring done
[cmake] Generating done

• Configurations in c_cpp_properties.json

{
    "configurations": [
        {
            "name": "Linux",
            "includePath": [
                "/opt/microchip/xc16/v1.70/support/**",
                "${workspaceFolder}/**"
            ],
            "browse" :{
                "path": [
                    "/opt/microchip/xc16/v1.70/support/**",
                    "${workspaceFolder}/**"
                ]
            },
            "defines": [],
            "compilerPath": "/opt/microchip/xc16/v1.70/bin/xc16-gcc",
            "cStandard": "c99",
            "intelliSenseMode": "linux-gcc-x64",
            "configurationProvider": "ms-vscode.cmake-tools",
            "compileCommands": "${workspaceFolder}/build/compile_commands.json"
        }
    ],
    "version": 4
}

• Logs from running C/C++: Log Diagnostics from the VS Code command palette

-------- Diagnostics - 5/17/2021, 7:43:23 PM
Version: 1.3.1
Current Configuration:
{
    "name": "Linux",
    "includePath": [
        "/opt/microchip/xc16/v1.70/support/**",
        "${workspaceFolder}/**"
    ],
    "browse": {
        "path": [
            "/opt/microchip/xc16/v1.70/support/**",
            "${workspaceFolder}/**"
        ],
        "limitSymbolsToIncludedHeaders": true
    },
    "defines": [],
    "compilerPath": "/opt/microchip/xc16/v1.70/bin/xc16-gcc",
    "cStandard": "c99",
    "intelliSenseMode": "linux-gcc-x64",
    "configurationProvider": "ms-vscode.cmake-tools",
    "compileCommands": "${workspaceFolder}/build/compile_commands.json",
    "compilerArgs": [],
    "intelliSenseModeIsExplicit": true,
    "cStandardIsExplicit": true,
    "cppStandardIsExplicit": true,
    "compilerPathIsExplicit": true
}
Custom browse configuration: 
{
    "browsePath": [
        "/root/Devel/PICo24_SDK/Boards/PotatoPi_PICo24",
        "/root/Devel/PICo24_SDK/Components",
        "/root/Devel/PICo24_SDK/Components/PICo24/Core",
        "/root/Devel/PICo24_SDK/Components/PICo24",
        "/root/Devel/PICo24_SDK/Components/PICo24/Peripherals/EXT_INT",
        "/root/Devel/PICo24_SDK/Components/PICo24/Peripherals/I2C",
        "/root/Devel/PICo24_SDK/Components/PICo24/Peripherals/SPI",
        "/root/Devel/PICo24_SDK/Components/PICo24/Peripherals/UART",
        "/root/Devel/PICo24_SDK/Components/PICo24/Peripherals/USB/Device",
        "/root/Devel/PICo24_SDK/Components/PICo24/Peripherals/USB/Host",
        "/root/Devel/PICo24_SDK/Components/PICo24/Peripherals/USB",
        "/root/Devel/PICo24_SDK/Components/PICo24/UnixAPI",
        "/root/Devel/PICo24_SDK"
    ],
    "standard": "gnu99",
    "compilerPath": "/opt/microchip/xc16/v1.70/bin/xc16-gcc",
    "compilerArgs": [
        "-fno-lto",
        "-fno-strict-aliasing",
        "-Wcast-align",
        "-omf=elf",
        "-DXPRJ_default=default",
        "-legacy-libc",
        "-msmart-io=1",
        "-msfr-warn=off",
        "-g",
        "-Os",
        "-std=gnu99",
        "-mcpu=\\\"24FJ256GB206\\\""
    ]
}
Custom configurations:
[ /root/Devel/PICo24_SDK/main.c ]
{
    "defines": [
        "XPRJ_default=default"
    ],
    "standard": "gnu99",
    "includePath": [
        "/root/Devel/PICo24_SDK/Boards/PotatoPi_PICo24",
        "/root/Devel/PICo24_SDK/Components"
    ],
    "compilerPath": "/opt/microchip/xc16/v1.70/bin/xc16-gcc",
    "compilerArgs": [
        "-fno-lto",
        "-fno-strict-aliasing",
        "-Wcast-align",
        "-omf=elf",
        "-DXPRJ_default=default",
        "-legacy-libc",
        "-msmart-io=1",
        "-msfr-warn=off",
        "-g",
        "-Os",
        "-std=gnu99",
        "-mcpu=\\\"24FJ256GB206\\\""
    ]
}
Translation Unit Mappings:
[ /root/Devel/PICo24_SDK/main.c ]:
    /root/Devel/PICo24_SDK/Components/PICo24/PICo24.h
Translation Unit Configurations:
[ /root/Devel/PICo24_SDK/main.c ]:
    Process ID: 4035
    Memory Usage: 20 MB
    Includes:
        /root/Devel/PICo24_SDK/Boards/PotatoPi_PICo24
        /root/Devel/PICo24_SDK/Components
        /usr/include/x86_64-linux-gnu/c++/8
        /usr/include/newlib/c++/7.3.1
        /usr/include/c++/8
        /usr/local/include
        /usr/lib/llvm-7/lib/clang/7.0.1/include
        /usr/include/x86_64-linux-gnu
        /usr/include/newlib
        /usr/include
    Defines:
        XPRJ_default=default
        XPRJ_default=default
    Standard Version: c99
    IntelliSense Mode: linux-gcc-x64
    Other Flags:
        --gcc
        --gnu_version=100000
Total Memory Usage: 20 MB
Browse Paths from compile_commands.json, from workspace folder: /root/Devel/PICo24_SDK
    /root/Devel/PICo24_SDK
    /root/Devel/PICo24_SDK/Boards/PotatoPi_PICo24
    /root/Devel/PICo24_SDK/Components
    /root/Devel/PICo24_SDK/Components/PICo24
    /root/Devel/PICo24_SDK/Components/PICo24/Core
    /root/Devel/PICo24_SDK/Components/PICo24/Peripherals/EXT_INT
    /root/Devel/PICo24_SDK/Components/PICo24/Peripherals/I2C
    /root/Devel/PICo24_SDK/Components/PICo24/Peripherals/SPI
    /root/Devel/PICo24_SDK/Components/PICo24/Peripherals/UART
    /root/Devel/PICo24_SDK/Components/PICo24/Peripherals/USB
    /root/Devel/PICo24_SDK/Components/PICo24/Peripherals/USB/Device
    /root/Devel/PICo24_SDK/Components/PICo24/Peripherals/USB/Host
    /root/Devel/PICo24_SDK/Components/PICo24/UnixAPI

------- Workspace parsing diagnostics -------
Number of files discovered (not excluded): 49455

• Logs from the language server logging

File exclude: **/.vscode
File exclude: **/.git
File exclude: **/.svn
File exclude: **/.hg
File exclude: **/CVS
File exclude: **/.DS_Store
Search exclude: **/node_modules
Search exclude: **/bower_components
Search exclude: **/*.code-search
Populate include completion cache.
Discovering files...
  Processing folder (recursive): /usr/local/include/
  Processing folder (recursive): /usr/lib/llvm-7/lib/clang/7.0.1/include/
  Processing folder (recursive): /usr/include/
  Processing folder (recursive): /root/Devel/PICo24_SDK/
  Discovering files: 49486 file(s) processed
  0 file(s) removed from database
Done discovering files.
Parsing open files...
Parsing remaining files...
  Parsing: 0 files(s) processed
Done parsing remaining files.
Done parsing open files.
idle loop: reparsing the active document
Checking for syntax errors: file:///root/Devel/PICo24_SDK/main.c
Queueing IntelliSense update for files in translation unit of: /root/Devel/PICo24_SDK/main.c
Error squiggle count: 66
Update IntelliSense time (sec): 0.254
terminating child process: 6746
terminating child process: 6748
Checking for syntax errors: file:///root/Devel/PICo24_SDK/Components/PICo24/PICo24.h
Queueing IntelliSense update for files in translation unit of: /root/Devel/PICo24_SDK/main.c
idle loop: reparsing the active document
Checking for syntax errors: file:///root/Devel/PICo24_SDK/Components/PICo24/PICo24.h
Queueing IntelliSense update for files in translation unit of: /root/Devel/PICo24_SDK/main.c
0 include path suggestion(s) discovered.
Error squiggle count: 65
Error squiggle count: 11
terminating child process: 6753
Update IntelliSense time (sec): 0.609
0 include path suggestion(s) discovered.

• xc16-gcc preprocessor output:

➜  build git:(master) ✗ /opt/microchip/xc16/v1.70/bin/xc16-gcc -v -E -dD empty.c
Microchip Language Tool Shell Version 1.70 (Build date: Mar  2 2021).
Copyright (c) 2012-2017 Microchip Technology Inc. All rights reserved
Using built-in specs.
COLLECT_GCC=/opt/microchip/xc16/v1.70/bin/bin/elf-gcc
Target: pic30-elf
Configured with: /home/xc16/release-builds/build_20210302/src/XC_GCC/gcc/configure --build=x86_64-linux --target=pic30-elf --disable-lto --disable-threads --disable-libmudflap --disable-libssp --disable-libstdcxx-pch --disable-hosted-libstdcxx --with-gnu-as --with-gnu-ld --enable-languages=c --disable-nls --disable-libgomp --without-headers --disable-libffi --disable-bootstrap --prefix=/bin --libexecdir=/bin --program-prefix=pic30- --with-libelf=/home/xc16/release-builds/build_20210302/bin/XC_GCC-elf-linux64-xclm/host-libs/ --with-dwarf2 --with-gmp=/home/xc16/release-builds/build_20210302/bin/XC_GCC-elf-linux64-xclm/host-libs --with-ppl=/home/xc16/release-builds/build_20210302/bin/XC_GCC-elf-linux64-xclm/host-libs --with-cloog=/home/xc16/release-builds/build_20210302/bin/XC_GCC-elf-linux64-xclm/host-libs --with-zlib=/home/xc16/release-builds/build_20210302/bin/XC_GCC-elf-linux64-xclm/host-libs --with-bugurl=https://www.microchip.com/technical-support --with-host-libstdcxx=
Thread model: single
gcc version 4.5.1 (XC16, Microchip v1.70) Build date: Mar  2 2021 (Microchip Technology) 
COLLECT_GCC_OPTIONS='-v' '-E' '-dD' '-mlegacy-libc'
 /opt/microchip/xc16/v1.70/bin/bin/../xc16-cc1 -E -quiet -v -iprefix /opt/microchip/xc16/v1.70/bin/bin/../pic30-elf/4.5.1/ empty.c -mresource=/opt/microchip/xc16/v1.70/bin/bin/../c30_device.info -omf=elf -mlegacy-libc -dD
Microchip Language Tool Shell Version 1.70 (Build date: Mar  2 2021).
Copyright (c) 2012-2017 Microchip Technology Inc. All rights reserved
ignoring nonexistent directory "/opt/microchip/xc16/v1.70/bin/bin/../pic30-elf/4.5.1/include"
ignoring nonexistent directory "/opt/microchip/xc16/v1.70/bin/bin/../pic30-elf/4.5.1/include-fixed"
ignoring nonexistent directory "/opt/microchip/xc16/v1.70/bin/bin/../pic30-elf/4.5.1/../../../../pic30-elf/sys-include"
ignoring nonexistent directory "/opt/microchip/xc16/v1.70/bin/bin/../pic30-elf/4.5.1/../../../../pic30-elf/include"
ignoring nonexistent directory "/root/Downloads/xc16_v1.70.src/v1.70.src/install-linux64/bin/lib/gcc/pic30-elf/4.5.1/include"
ignoring nonexistent directory "/root/Downloads/xc16_v1.70.src/v1.70.src/install-linux64/bin/lib/gcc/pic30-elf/4.5.1/include-fixed"
ignoring nonexistent directory "/root/Downloads/xc16_v1.70.src/v1.70.src/install-linux64/bin/pic30-elf/sys-include"
ignoring nonexistent directory "/root/Downloads/xc16_v1.70.src/v1.70.src/install-linux64/bin/pic30-elf/include"
#include "..." search starts here:
#include <...> search starts here:
 /opt/microchip/xc16/v1.70/bin/bin/../../include/lega-c
 /opt/microchip/xc16/v1.70/bin/bin/../../support/generic/h
End of search list.
# 1 "empty.c"
# 1 "<built-in>"
#define __STDC__ 1
#define __STDC_HOSTED__ 1
#define __GNUC__ 4
#define __GNUC_MINOR__ 5
#define __GNUC_PATCHLEVEL__ 1
#define __SIZE_TYPE__ unsigned int
#define __PTRDIFF_TYPE__ int
#define __WCHAR_TYPE__ short unsigned int
#define __WINT_TYPE__ unsigned int
#define __INTMAX_TYPE__ long long int
#define __UINTMAX_TYPE__ long long unsigned int
#define __CHAR16_TYPE__ short unsigned int
#define __CHAR32_TYPE__ unsigned int
#define __GXX_ABI_VERSION 1002
#define __USING_SJLJ_EXCEPTIONS__ 1
#define __SCHAR_MAX__ 127
#define __SHRT_MAX__ 32767
#define __INT_MAX__ 32767
#define __LONG_MAX__ 2147483647L
#define __LONG_LONG_MAX__ 9223372036854775807LL
#define __WCHAR_MAX__ 65535U
#define __WCHAR_MIN__ 0U
#define __WINT_MAX__ 65535U
#define __WINT_MIN__ 0U
#define __PTRDIFF_MAX__ 32767
#define __SIZE_MAX__ 65535U
#define __CHAR_BIT__ 8
#define __INTMAX_MAX__ 9223372036854775807LL
#define __INTMAX_C(c) c ## LL
#define __UINTMAX_MAX__ 18446744073709551615ULL
#define __UINTMAX_C(c) c ## ULL
#define __FLT_EVAL_METHOD__ 0
#define __DEC_EVAL_METHOD__ 2
#define __FLT_RADIX__ 2
#define __FLT_MANT_DIG__ 24
#define __FLT_DIG__ 6
#define __FLT_MIN_EXP__ (-125)
#define __FLT_MIN_10_EXP__ (-37)
#define __FLT_MAX_EXP__ 128
#define __FLT_MAX_10_EXP__ 38
#define __FLT_MAX__ 3.4028234663852886e+38F
#define __FLT_MIN__ 1.1754943508222875e-38F
#define __FLT_EPSILON__ 1.1920928955078125e-7F
#define __FLT_DENORM_MIN__ 1.4012984643248171e-45F
#define __FLT_HAS_DENORM__ 1
#define __FLT_HAS_INFINITY__ 1
#define __FLT_HAS_QUIET_NAN__ 1
#define __DBL_MANT_DIG__ 24
#define __DBL_DIG__ 6
#define __DBL_MIN_EXP__ (-125)
#define __DBL_MIN_10_EXP__ (-37)
#define __DBL_MAX_EXP__ 128
#define __DBL_MAX_10_EXP__ 38
#define __DBL_MAX__ ((double)3.4028234663852886e+38L)
#define __DBL_MIN__ ((double)1.1754943508222875e-38L)
#define __DBL_EPSILON__ ((double)1.1920928955078125e-7L)
#define __DBL_DENORM_MIN__ ((double)1.4012984643248171e-45L)
#define __DBL_HAS_DENORM__ 1
#define __DBL_HAS_INFINITY__ 1
#define __DBL_HAS_QUIET_NAN__ 1
#define __LDBL_MANT_DIG__ 53
#define __LDBL_DIG__ 15
#define __LDBL_MIN_EXP__ (-1021)
#define __LDBL_MIN_10_EXP__ (-307)
#define __LDBL_MAX_EXP__ 1024
#define __LDBL_MAX_10_EXP__ 308
#define __DECIMAL_DIG__ 17
#define __LDBL_MAX__ 1.7976931348623157e+308L
#define __LDBL_MIN__ 2.2250738585072014e-308L
#define __LDBL_EPSILON__ 2.2204460492503131e-16L
#define __LDBL_DENORM_MIN__ 4.9406564584124654e-324L
#define __LDBL_HAS_DENORM__ 1
#define __LDBL_HAS_INFINITY__ 1
#define __LDBL_HAS_QUIET_NAN__ 1
#define __DEC32_MANT_DIG__ 7
#define __DEC32_MIN_EXP__ (-94)
#define __DEC32_MAX_EXP__ 97
#define __DEC32_MIN__ 1E-95DF
#define __DEC32_MAX__ 9.999999E96DF
#define __DEC32_EPSILON__ 1E-6DF
#define __DEC32_SUBNORMAL_MIN__ 0.000001E-95DF
#define __DEC64_MANT_DIG__ 16
#define __DEC64_MIN_EXP__ (-382)
#define __DEC64_MAX_EXP__ 385
#define __DEC64_MIN__ 1E-383DD
#define __DEC64_MAX__ 9.999999999999999E384DD
#define __DEC64_EPSILON__ 1E-15DD
#define __DEC64_SUBNORMAL_MIN__ 0.000000000000001E-383DD
#define __DEC128_MANT_DIG__ 34
#define __DEC128_MIN_EXP__ (-6142)
#define __DEC128_MAX_EXP__ 6145
#define __DEC128_MIN__ 1E-6143DL
#define __DEC128_MAX__ 9.999999999999999999999999999999999E6144DL
#define __DEC128_EPSILON__ 1E-33DL
#define __DEC128_SUBNORMAL_MIN__ 0.000000000000000000000000000000001E-6143DL
#define __REGISTER_PREFIX__ 
#define __USER_LABEL_PREFIX__ _
#define __VERSION__ "4.5.1 (XC16, Microchip v0_00) Build date: May  5 2021"
#define __GNUC_GNU_INLINE__ 1
#define __NO_INLINE__ 1
#define __FINITE_MATH_ONLY__ 0
#define __PRAGMA_REDEFINE_EXTNAME 1
#define __SIZEOF_INT__ 2
#define __SIZEOF_LONG__ 4
#define __SIZEOF_LONG_LONG__ 8
#define __SIZEOF_SHORT__ 2
#define __SIZEOF_FLOAT__ 4
#define __SIZEOF_DOUBLE__ 4
#define __SIZEOF_LONG_DOUBLE__ 8
#define __SIZEOF_SIZE_T__ 2
#define __SIZEOF_WCHAR_T__ 2
#define __SIZEOF_WINT_T__ 2
#define __SIZEOF_PTRDIFF_T__ 2
#define __SIZEOF_POINTER__ 2
#define __OPTIMIZATION_LEVEL__ 0
#define __LARGE_ARRAYS__ 0
#define __BUILTIN_ITTYPE 1
#define __C30_VERSION__ 0
#define __XC16_VERSION 0
#define __XC16_VERSION__ 0
#define __XC__ 1
#define __XC16 1
#define __C30 1
#define __dsPIC30 1
#define __C30__ 1
#define __XC16__ 1
#define __dsPIC30__ 1
#define __XC16ELF 1
#define __C30ELF 1
#define __dsPIC30ELF 1
#define __C30ELF__ 1
#define __XC16ELF__ 1
#define __dsPIC30ELF__ 1
#define C30 1
#define XC16 1
#define dsPIC30 1
#define __HAS_DSP__ 1
#define __BIGGEST_ALIGNMENT__ 2
# 1 "<command-line>"
# 1 "empty.c"
PIC30_COMPILER_PATH=/opt/microchip/xc16/v1.70/bin/bin/../
PIC30_LIBRARY_PATH=/opt/microchip/xc16/v1.70/bin/bin/../:/opt/microchip/xc16/v1.70/bin/bin/../../lib/:/opt/microchip/xc16/v1.70/bin/bin/../../lib/PIC24E/:/opt/microchip/xc16/v1.70/bin/bin/../../support/PIC24E/gld/:/opt/microchip/xc16/v1.70/bin/bin/../../lib/PIC24F/:/opt/microchip/xc16/v1.70/bin/bin/../../support/PIC24F/gld/:/opt/microchip/xc16/v1.70/bin/bin/../../lib/PIC24H/:/opt/microchip/xc16/v1.70/bin/bin/../../support/PIC24H/gld/:/opt/microchip/xc16/v1.70/bin/bin/../../lib/dsPIC30F/:/opt/microchip/xc16/v1.70/bin/bin/../../support/dsPIC30F/gld/:/opt/microchip/xc16/v1.70/bin/bin/../../support/dsPIC33C/gld/:/opt/microchip/xc16/v1.70/bin/bin/../../lib/dsPIC33E/:/opt/microchip/xc16/v1.70/bin/bin/../../support/dsPIC33E/gld/:/opt/microchip/xc16/v1.70/bin/bin/../../lib/dsPIC33F/:/opt/microchip/xc16/v1.70/bin/bin/../../support/dsPIC33F/gld/
COLLECT_GCC_OPTIONS='-v' '-E' '-dD' '-mlegacy-libc'

Screenshots

[sean-mcmanus]

With C_Cpp.loggingLevel set to "Debug" can you look in the "C/C++" logging for a failure message after "Compiler query command line: "? I don't see that in your existing logging.

[ReimuNotMoe]

With C_Cpp.loggingLevel set to "Debug" can you look in the "C/C++" logging for a failure message after "Compiler query command line: "? I don't see that in your existing logging.

The logs are extremely long, so I didn't include all of them.

Here they are:

Attempting to get defaults from C compiler in "compilerPath" property: '/opt/microchip/xc16/v1.70/bin/xc16-gcc'
Querying compiler for default C++ language standard using command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -x c++ -E -dM /dev/null
terminating child process: 55881
Querying compiler for default C language standard using command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -x c -E -dM /dev/null
terminating child process: 55885
Querying compiler's default target using command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -dumpmachine
Compiler returned default target value: pic30-elf

terminating child process: 55891
Unhandled default compiler target value detected: pic30-elf

Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=c99 -Wp,-v -E -dD -x c -m64  /dev/null
Compiler does not support 64-bit. Falling back to 32-bit intelliSenseMode.
terminating child process: 55895
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=c99 -Wp,-v -E -dD -x c -m32  /dev/null
Failed to query compiler. Falling back to no bitness.
terminating child process: 55901
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=c99 -Wp,-v -E -dD -x c   /dev/null
terminating child process: 55907
Shutting down IntelliSense server: /root/Devel/PICo24_SDK/main.c
  Folder: /usr/local/include/ will be indexed
  Folder: /usr/lib/llvm-7/lib/clang/7.0.1/include/ will be indexed
  Folder: /usr/include/ will be indexed
  Folder: /root/Devel/PICo24_SDK/ will be indexed
Attempting to get defaults from C++ compiler in "compilerPath" property: '/opt/microchip/xc16/v1.70/bin/xc16-gcc'
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=c++17 -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55913
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=c++1z -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55916
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=c++14 -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55919
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=c++1y -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55922
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=c++11 -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55925
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=c++0x -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55928
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=c++03 -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55931
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=c++98 -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55934
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=gnu++20 -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55937
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=gnu++2a -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55940
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=gnu++17 -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55943
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=gnu++1z -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55946
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=gnu++14 -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55949
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=gnu++1y -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55952
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=gnu++11 -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55955
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=gnu++0x -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55958
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=gnu++03 -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55961
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc" -std=gnu++98 -Wp,-v -E -dD -x c++ -m64  /dev/null
terminating child process: 55964
Compiler query command line: "/opt/microchip/xc16/v1.70/bin/xc16-gcc"  -Wp,-v -E -dD -x c++ -m64  /dev/null
Failed to query default include paths and defines for /opt/microchip/xc16/v1.70/bin/xc16-gcc.
terminating child process: 55967

[Colengms]

Curious. It looks like the compiler query is insisting on adding -m64 and not falling back to -m32 or 'no bitness' for some reason, when querying as a C++ compiler. Querying as a C compiler works fine.

Does the XC16 compiler support only C, and not C++? At this link, I noticed the following: C++ only available in MPLAB XC32++ compilers

It would seem likely that this issue is lack of support for querying gcc-like C compilers that do not support C++. @ReimuNotMoe Could you confirm that the compiler you are using does not support C++?

[ReimuNotMoe]

Curious. It looks like the compiler query is insisting on adding -m64 and not falling back to -m32 or 'no bitness' for some reason, when querying as a C++ compiler. Querying as a C compiler works fine.

Does the XC16 compiler support only C, and not C++? At this link, I noticed the following: C++ only available in MPLAB XC32++ compilers

It would seem likely that this issue is lack of support for querying gcc-like C compilers that do not support C++. @ReimuNotMoe Could you confirm that the compiler you are using does not support C++?

Yes. Only C is officially supported by XC16, however there are unofficial community support for C++98 (by modifying the XC16 build script).

There are many other compilers that follows GCC's usages and only supports C, such as some 8051 MCU compilers.

I think you can simply check if CMAKE_CXX_COMPILER is set in CMakeLists.txt or if compilers.CXX is set for a particular kit defined in cmake-tools-kits.json.