Let's break down the given code snippet: ### The code: ```c #include "macro.h" #if...

Let's break down the given code snippet:

The code:

#include "macro.h"
#if _MSC_VER < 1900
#ifndef __GNUC__
int lround(double d)

Explanation:

1. #include "macro.h":

   • This line includes a header file named macro.h. This likely contains definitions, macros, or declarations that will be used later in the code.

2. #if _MSC_VER < 1900:

   • _MSC_VER is a predefined macro provided by Microsoft Visual Studio compilers. It specifies the version of the compiler in use.
   • This conditional checks if the compiler version is less than 1900. This is used to ensure compatibility or apply different code paths based on the compiler version.

3. #ifndef __GNUC__:

   • __GNUC__ is a predefined macro provided by GCC (GNU Compiler Collection).
   • This conditional checks if the code is not being compiled with the GCC compiler.

4. int lround(double d):

   • This is a declaration for a function lround that takes a double as a parameter and returns an int.
   • The actual function definition and implementation would likely follow this declaration.

Overall Purpose:

The code snippet:

• Starts by including a header file (macro.h).
• Checks if the Microsoft Visual Studio compiler version is less than 1900 and ensures the code does not target GCC.
• If both conditions are satisfied, it declares the lround function.

The snippet seems related to providing a custom implementation of the lround function for environments where it may not be natively available, specifically Microsoft compilers earlier than version 1900 and excluding GCC compilers.