Porting and Upgrading Visual C++ Projects with MSVC

Visual Studio 2015 → v140  (14.0.x)
Visual Studio 2017 → v141  (14.1.x)
Visual Studio 2019 → v142  (14.2.x)
Visual Studio 2022 → v143  (14.3.x)
Visual Studio 2026 → v145  (14.5.x)

// A library built with VS 2015 /MD can be linked into a VS 2026 application:
// lib_2015.lib   (built with v140, /MD) ← works with VS 2026 linker
// app_2026.exe   (built with v143, /MD) ← can link lib_2015.lib

VS 2008 project → Open in VS 2010 (upgrades to MSBuild .vcxproj format)
                → Then open in latest Visual Studio (retarget toolset)

// DEPRECATED — triggers C4996 warning:
access("file.txt", 0);     // Use _access instead
unlink("file.txt");        // Use _unlink instead
strdup(str);               // Use _strdup instead
getcwd(buf, size);         // Use _getcwd instead
strcpy(dest, src);         // Use strcpy_s instead
sprintf(buf, fmt, ...);    // Use sprintf_s instead

// CORRECT replacements:
_access("file.txt", 0);
_unlink("file.txt");
_strdup(str);
_getcwd(buf, size);
strcpy_s(dest, sizeof(dest), src);
sprintf_s(buf, sizeof(buf), fmt, ...);

// Non-standard: two-phase name lookup not previously enforced
template<typename T>
void foo() {
    bar(); // In /permissive- mode, 'bar' must be declared before the template
}

// Fix: forward-declare bar() before the template definition
void bar();
template<typename T>
void foo() { bar(); }

# Temporarily relax conformance during transition:
cl /permissive myfile.cpp

# Full conformance mode (default in newer toolsets):
cl /permissive- myfile.cpp

// VS 2015+: std::bind no longer allows nested bind expressions
// without explicit std::ref wrapping

// VS 2017+: std::vector<bool> is no longer assignable in certain contexts

// Use explicit types to avoid ambiguity:
std::vector<bool> flags = {true, false, true};
bool val = static_cast<bool>(flags[0]); // Explicit cast required in some contexts

// Suppressing specific warnings during transition:
#pragma warning(push)
#pragma warning(disable: 4996) // 'function': deprecated
#include <legacy_header.h>
#pragma warning(pop)

// Or per-file via project properties:
// C/C++ → Advanced → Disable Specific Warnings: 4996

// BROKEN: Direct use of internal CRT symbols (not public API)
extern "C" int _cdecl __stdio_common_vfprintf(...);

// FIX: Use the public API — printf, fprintf, etc.
printf("%s\n", message);

<!-- .vcxproj: Target an older toolset while using the latest IDE -->
<PropertyGroup>
  <PlatformToolset>v140</PlatformToolset>  <!-- VS 2015 toolset -->
</PropertyGroup>