Linux header file not recognized in Visual Studio

Question

When including a Linux header file, ucontext.h in this case, in a Linux C++ Project on Visual Studio 2017 for my C program, it does not recognize the header file. Even when I include sys/ucontext.h, it does not recognize functions that I should be able to use for a ucontext_t object, such as getContext() and setContext(). Shouldn't I be able to use these functions in a Linux C++ project?

Code I'm writing:

#include <stddef.h>
#include <string.h>
#include <sys/ucontext.h> 
// If I use ucontext.h instead, it gives the error: cannot open source file ucontext.h

//TCB structure
typedef struct TCB_t {
    struct TCB_t     *next;
    struct TCB_t     *prev;
    ucontext_t      context;
} TCB_t;


void init_TCB(TCB_t *tcb, void *function, void *stackP, int stack_size)
{
    memset(tcb, '\0', sizeof(TCB_t));   
    tcb->context.uc_stack.ss_sp = stackP;
    tcb->context.uc_stack.ss_size = (size_t)stack_size;

    int c = getcontext(tcb->context); // Cannot resolve field getcontext()
}

Answer 1

On this answer to do the following you need Visual Studio Community 2017 15.9.7+ - Tested this solution on Visual Studio Enterprise 2019 Preview 4.

Visual Studio needs to download all remote headers in your localmachine for correct behavior of intellisense.

New method 'rsync_ssh' doesn't download all headers. You can use old method .zip via sftp_ssh.

0. Add remote connection.
Tools->Options->Cross Platform->Connection Manager

1. Select your connection Update from Tools->Options->Cross Platform->Connection Manager->Remote Headers Intellisense Manager. Next click on Explore button.

2. C:\Users[YourUser]\AppData\Local\Microsoft\Linux\HeaderCache\1.0[IdNumber] Rename the HeaderCache settings.xml.unused file to settings.xml

3. In the settings.xml file Change the syncMethod to sftp_ssh.

4. Update headers cache from Tools->Options->Cross Platform->Connection Manager->Remote Headers Intellisense Manager. 5. Enjoy.

Before

After

Answer 2

On my Linux system (Debian Jessie) ucontext.h is in usr/include which in turn includes sys/ucontext.h which gcc will find in usr/include/i386-linux-gnu/sys. The first defines the functions getcontext and setcontext. The second defines the data structures ucontext_t etc.

On the Windows host, VCLinux has installed a copy of the second ucontext.h (which defines the data structures) in C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\Linux\include\usr\include\x86_64-linux-gnu\sys . But the first ucontext.h is not present.

VCLinux/Visual Studio will compile and run this program on the Linux remote:

#include <ucontext.h>
#include <iostream>
int main()
{
   ucontext ucxt;
   ::getcontext (&ucxt);
   std::cout << ucxt.uc_flags << std::endl;
   return 0;
}

But IntelliSense will not know about the functions getcontext and setcontext or the associated data structures. So you will get little red squiggles under the names and no completion assistance.

You can take a copy of the first ucontext.h and put it in C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\Linux\include\usr\include on your Windows host. Then everything will work as it should. And you could raise an issue for the missing header on the VCLinux GitHub site.

Note: Windows paths are for Visual Studio 2015. They will be different for 2017.

Applies to VCLinux 1.0.6.

==============

Update 10-Apr-18

Microsoft have addressed the issue of differences in standard include file locations between Linux systems. As explained in this Visual C++ blog post, the headers specific to the GCC setup are copied from the Linux remote and stored on the Windows host on a per-connection basis.