Cannot compile program with MSMPI and GCC

Question

I'm trying to compile a MSMPI program in C with gcc.

Here is what I am including in my code:

#define MSMPI_NO_SAL

#include "mpi.h"
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

I'm using Vscode with the following task:

{
  "version": "2.0.0",
  "tasks": [{
    "type": "shell",
    "label": "C/C++: gcc.exe build active file",
    "command": "C:\\MinGW\\bin\\gcc.exe",
    "args": ["-g", "${file}","-I","C:\\Program Files (x86)\\Microsoft SDKs\\MPI\\Lib\\x64","-I","C:\\Program Files (x86)\\Microsoft SDKs\\MPI\\Include",  "-o", "${fileDirname}\\${fileBasenameNoExtension}.exe"],
    "options": {
      "cwd": "${workspaceFolder}"
    },
    "problemMatcher": ["$gcc"],
    "group": {
      "kind": "build",
      "isDefault": true
    }
  }]
}

However, when trying to compile, I get the following error for my code:

In file included from d:\Documents\1.Ecole\University\Undergrad\Fall 2020\COMP 428\ass1\pi_est_parallel.c:5:
C:\Program Files (x86)\Microsoft SDKs\MPI\Include/mpi.h:4617:5: error: unknown type name '_Out_writes_'; did you mean '_mpi_writes_'?
 4617 |     _Out_writes_(maxprocs) int array_of_errcodes[]
      |     ^~~~~~~~~~~~
      |     _mpi_writes_
C:\Program Files (x86)\Microsoft SDKs\MPI\Include/mpi.h:4629:5: error: unknown type name '_Out_writes_'; did you mean '_mpi_writes_'?
 4629 |     _Out_writes_(maxprocs) int array_of_errcodes[]
      |     ^~~~~~~~~~~~
      |     _mpi_writes_
The terminal process "C:\WINDOWS\System32\WindowsPowerShell\v1.0\powershell.exe -Command C:\MinGW\bin\gcc.exe -g 'd:\Documents\1.Ecole\University\Undergrad\Fall 2020\COMP 428\ass1\pi_est_parallel.c' -I 'C:\Program Files (x86)\Microsoft SDKs\MPI\Lib\x64' -I 'C:\Program Files (x86)\Microsoft SDKs\MPI\Include' -o 'd:\Documents\1.Ecole\University\Undergrad\Fall 2020\COMP 428\ass1\pi_est_parallel.exe'" terminated with exit code: 1.
Terminal will be reused by tasks, press any key to close it.

Am I forgetting to include something when compiling?

Answer 1

This is a known issue in the Microsoft mpi.h header file:

• Build errors with MSMPI_NO_SAL

The issue references a simple patch adding _Out_writes_ to fix this. You can mirror this in your own code by adding

#define _Out_writes_(x)

before you include mpi.h if you cannot upgrade to the latest version.