Date: 2020apr24 Update: 2026sep23 Language: C/C++ Q. C/C++: Conditional compile by OS (Windows or Linux) A. Use predefined macros like this:

#ifdef __linux__ // We are compiling on Linux #elif defined(_WIN32) || defined(_WIN64) // We are compiling on Windows #else // Not windows or Linux! #endif

Here's an example use:

char getNativeSlash() { #if defined(_WIN32) || defined(_WIN64) return '\\'; #else return '/'; #endif }

Or that could be done:

#if defined(_WIN32) || defined(_WIN64) const char gNativeSlash = '\\'; #else const char gNativeSlash = '/'; #endif

Full Example:

#include <stdio.h> char getNativeSlash() { #if defined(_WIN32) || defined(_WIN64) return '\\'; #else return '/'; #endif } int main() { printf("The native slash is %c\n", getNativeSlash()); }

Output (On Linux):

The native slash is /