Compiler errors in standard C library headers in VS2015 - Visual C++ Console Application project - visual-c++

Question

I recently created a VS2015 solution to continue development on a C++ project I had been working on. Whenever I try to build the project, I get hundreds of errors from standard C library header files such as string.h, stdio.h, etc.
To try to get to the root of the problem, I created a new, very basic, VC++ win32 console application project, wondering if I'd see the same compiler errors. Here is the code (ConsoleApplication1.cpp):
#include <string>
#include <iostream>
int main()
{
std::string s = "some data to print...";
std::cout << "Printing: " << s.c_str() << std::endl;
return 0;
}
When I attempt to compile this, I get 150+ errors, like this:
1>------ Build started: Project: ConsoleApplication1, Configuration: Release Win32 ------
1> stdafx.cpp
1>C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\stdio.h(309): error C2144: syntax error: 'int' should be preceded by ';'
1>C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\stdio.h(309): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\stdio.h(311): error C2144: syntax error: 'int' should be preceded by ';'
1>C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\stdio.h(311): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\stdio.h(311): error C2086: 'int _CRTIMP_ALTERNATIVE': redefinition
1> C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\stdio.h(309): note: see declaration of '_CRTIMP_ALTERNATIVE'
1>C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\stdio.h(317): error C2144: syntax error: 'int' should be preceded by ';'
1>C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\stdio.h(317): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\stdio.h(317): error C2086: 'int _CRTIMP_ALTERNATIVE': redefinition
1> C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\stdio.h(309): note: see declaration of '_CRTIMP_ALTERNATIVE'
1>C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\stdio.h(320): error C2144: syntax error: 'int' should be preceded by ';'
1>C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\stdio.h(320): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\stdio.h(320): error C2086: 'int _CRTIMP_ALTERNATIVE': redefinition
1> C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\stdio.h(309): note: see declaration of '_CRTIMP_ALTERNATIVE'
....etc
I have tried to 'repair' Microsoft VC++ 2015 Redistributable(x86) via the Windows 'Uninstall or change a program' utility, to no avail. I also tried to repair Visual Studio 2015 as a whole.
I'm on Windows 7.
Anyone have an idea what is going on here? Am I pointed to the wrong include directory or something?

Answer 1

It appears you have (some of) the headers from a previous version of VS installed in your VS2015 folder. The standard headers in VS2015 are stored off in a folder tied to the version of the CRT (something like c:\Program Files (x86)\Windows Kits\10\Include\10.0.10240.0\ucrt). Repairing or reinstalling VS2015 won't fix this.
I think you'll need to uninstall VS2015, completely delete the folder C:\Program Files (x86)\Microsoft Visual Studio 14.0, then reinstall it. This will likely break the other version (VS2013?) that is installed there, so you might want/need to uninstall that version instead, then repair VS2015.
The header that comes with VS2015 does not appear to have the "int _CRTIMP_ALTERNATIVE" listed in some of the error messages at those lines, while the one with VS2013 does.