#ifdef in C
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The #ifdef directive in C is used for conditional compilation.
It checks whether a particular macro is defined.
If the macro is defined, the code between #ifdef and #endif is included in the compilation; otherwise, it is skipped.
Syntax of #ifdef in C
#ifdef macro_name // code to be compiled if macro_name is defined #endif
Example:
#include<stdio.h>#define DEBUG 1 int main() { #ifdef DEBUG printf("Debugging is enabled.\n"); #endif printf("This line is always printed.\n"); return 0; }
Output:
Debugging is enabled. This line is always printed.
In this example:
The DEBUG macro is defined with a value of 1.
The #ifdef DEBUG directive checks if DEBUG is defined.
If DEBUG is defined, the message "Debugging is enabled. " is printed.
The message "This line is always printed." is printed regardless of whether DEBUG is defined or not.
Uses of ifdef in C
Debugging: It's commonly used to enable or disable debugging statements in the code.
#ifdef DEBUG printf("Debugging message: variable value = %d\n", variable); #endif
Platform-specific code: To write platform-specific code that is only compiled for certain platforms.
#ifdef __linux__ // Linux-specific code #endif
Feature toggles: To enable or disable certain features of the program based on configuration.
#if,def FEATURE_A // Code related to Feature A #endif
By using #ifdef, you can write more flexible and maintainable code that can be customized for different scenarios or platforms.
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