vscode report undefined symbol which has been actually included

Question

The source code is very simple.

#include <signal.h>

void main() {
    sigset_t set;
}

The signal.h has been included in which sigset_t should have been defined. But vscode still report a problem.

identifier "sigset_t" is undefined

The config file is as below.

{
    "configurations": [
        {
            "name": "Linux",
            "includePath": [
                "${workspaceFolder}/**"
            ],
            "defines": [],
            "compilerPath": "/usr/bin/gcc",
            "cStandard": "c11",
            "cppStandard": "c++98",
            "intelliSenseMode": "linux-clang-x64"
        }
    ],
    "version": 4
}

And the program can be successfully compiled with no error. Why does vscode report that error?

Answer 1

The problem here is that sigset_t is only defined if _POSIX_C_SOURCE is defined.

With the C standard that gcc uses by default, _POSIX_C_SOURCE is already defined. So compiling your program with gcc doesn't produce an error.

To solve this you can add "cStandard": "gnu11" to you config file, or add "defines": ["_POSIX_C_SOURCE=199309L"].

{
    "configurations": [
        {
            "name": "Linux",
            "includePath": [
                "${workspaceFolder}/**"
            ],
            "defines": [],
            "compilerPath": "/usr/bin/gcc",
            "cStandard": "gnu11",
            "cppStandard": "c++98",
            "intelliSenseMode": "linux-clang-x64"
        }
    ],
    "version": 4
}