How do you override a defined macro?

Asked by Last Modified  

12 Answers

Learn C Language

Follow 1
Answer

Please enter your answer

Chetan Santha

Professional Tutor with 15 years of experience.

We can use the #ifdef and #undef directive to undefine a previously defined macro.
Comments
Dislike Bookmark

#define MYMACRO(x) x*x //previously defined macro ... #ifdef MYMACRO #undef MYMACRO #define MYMACRO(x) x*x*x //new definition #endif int main() { printf("%d\n", MYMACRO(2)); return 0; }
Comments
Dislike Bookmark

You can't. The command line is handled before any source and header files. If a source file defines a macro, then it must not be defined before, and will get the new value from now on. The only way to change it, is to #undef and #define it again, at a later point. If you have access to a header...
read more
You can't. The command line is handled before any source and header files. If a source file defines a macro, then it must not be defined before, and will get the new value from now on. The only way to change it, is to #undef and #define it again, at a later point. If you have access to a header that is included after the definition, then you have a chance. read less
Comments
Dislike Bookmark

Science Expert, C & C++ Strong

You can use the #undef preprocessor directive to undefine (override) a previously defined macro. Many programmers like to ensure that their applications are using their own terms when defining symbols such as TRUE and FALSE. Your program can check to see whether these symbols have been defined already,...
read more
You can use the #undef preprocessor directive to undefine (override) a previously defined macro. Many programmers like to ensure that their applications are using their own terms when defining symbols such as TRUE and FALSE. Your program can check to see whether these symbols have been defined already, and if they have, you can override them with your own definitions of TRUE and FALSE. read less
Comments
Dislike Bookmark

How do you override a defined macro? in C programming How do you override a defined macro? You can use the #undef preprocessor directive to undefine (override) a previously defined macro. Many programmers like to ensure that their applications are using their own terms when defining symbols such as...
read more
How do you override a defined macro? in C programming How do you override a defined macro? You can use the #undef preprocessor directive to undefine (override) a previously defined macro. Many programmers like to ensure that their applications are using their own terms when defining symbols such as TRUE and FALSE. Your program can check to see whether these symbols have been defined already, and if they have, you can override them with your own definitions of TRUE and FALSE. The following portion of code shows how this task can be accomplished: ... #ifdef TRUE /* Check to see if TRUE has been defined yet */ #undef TRUE /* If so, undefine it */ #endif #define TRUE 1 /* Define TRUE the way we want it defined */ #ifdef FALSE /* Check to see if FALSE has been defined yet */ #undef FALSE /* If so, undefine it */ #endif #define FALSE !TRUE /* Define FALSE the way we want it defined */ ... In the preceding example, the symbols TRUE and FALSE are checked to see whether they have been defined yet. If so, they are undefined, or overridden, using the #undef preprocessor directive, and they are redefined in the desired manner. If you were to eliminate the #undef statements in the preceding example, the compiler would warn you that you have multiple definitions of the same symbol. By using this technique, you can avoid this warning and ensure that your programs are using valid symbol definitions. read less
Comments
Dislike Bookmark

website and mobile application development training, digital marketing training

Yes, You can use the #undef preprocessor directive to undefine (override) a previously defined macro
Comments
Dislike Bookmark

Computer & Maths Professor

You can use the #undef preprocessor directive to undefine (override) a previously defined macro.
Comments
Dislike Bookmark

C and linux Expert

You can use the #undef preprocessor directive to undefine (override) a previously defined macro. Many programmers like to ensure that their applications are using their own terms when defining symbols such as TRUE and FALSE.
Comments
Dislike Bookmark

LearnHowToLearn, Expert In Programming Languages

Just redefine it.
Comments
Dislike Bookmark

LearnHowToLearn, Expert In Programming Languages

#undef first the already defined macro and then redefine it. # define
Comments
Dislike Bookmark

View 10 more Answers

Related Questions

Who founded the C language? Why?
The C programming language was developed by Dennis Ritchie at Bell Labs in the early 1970s. Ritchie, along with his colleague Ken Thompson, created C as an evolution of the B programming...
Santosini
0 0
View Comments7
How do I get 6 power 13 in c language?
By using pow(6, 13). Don't forget to import math.h header file
Tanush
0 0
View Comments5
What is meaning of & in c language?
In the C family of languages, &x means “the address of x” and *y means “the value at the address y”.
Khushwunder
0 0
View Comments5
Is it possible to write big safe programs in C++?
yes. C++ is generally used to write system software. For example windows operating system are writeen in C++. Most of the operating system, device driver and antivirus programs are written by using C++.
Sapna
0 0
View Comments6
How do I start learning C programming and finish it in one month?
Use a book named "Let us C"by yashwant t kanetkar. Or simply by taking a class from teachers on urbanpro
Pallavi
0 0
View Comments8

Now ask question in any of the 1000+ Categories, and get Answers from Tutors and Trainers on UrbanPro.com

Ask a Question

Related Lessons

Everything about printf in C language
What is printf and from where it comes from in C code.? You must have used printf so many times in your Car programs but do you really know everything about printf? Let's see. What is the full form...

Ganesh Shinde

0 0
View Comments0
C Program-Temperature [conversion from farenheit to degree celsius]
//WAP to convert temperture from farenheit into degree celsius //Header files#include<stdio.h>#include<conio.h> //Main functrion void main(){ //Variable declaration of type float float...

Salim Ahmed Ansari

0 0
View Comments0
Can we store different data types in a stack?
Yesterday, one of my Facebook friend asked me this question. My answer is "yes", and in this post I will discuss how could we do this.I am a great supporter of working with unions and I will be using union...

Shiladitya Munshi

0 0
View Comments0
Working with C/C++ applications
Inorder to learn C and C++ programming languages one can work with various editors available.To name a few are the most popular one is turbo c++, DEV C++, Eclipse, NetBeans. Here are the screen shots...

Salim Ahmed Ansari

0 0
View Comments0
Tips of learning Java Language/Other Programming Languages
1.You should know the basic concept: If we talk about programming languages so basic concept are same in all the high level languages. So you should know the basic concept firstly then you can easily understand...
I

Icreative Solution

0 0
View Comments0

Recommended Articles

Lasya Infotech: An educational Training...

Lasya Infotech is a Hyderabad based IT training institute founded in 2016 by O Venkat. Believing in his innovation, passion and persistence and with a diverse blend of experience, he started his brainchild to deliver exemplary professional courses to aspiring candidates by honing their skills. Ever since the institute envisions...

Read full article >

Brilliant Academy, a reputed B. Tech Tuition...

Brilliant Academy is one of the reputed institutes for B.Tech tuition classes. This institute is specialised in delivering quality tuition classes for B.E, Engineering - all streams and Engineering diploma courses. Incorporated in 2012, Brillant Academy is a brainchild of Mr Jagadeesh. The main motto of the academy is to...

Read full article >

Make a Career as a BPO Professional

Business Process outsourcing (BPO) services can be considered as a kind of outsourcing which involves subletting of specific functions associated with any business to a third party service provider. BPO is usually administered as a cost-saving procedure for functions which an organization needs but does not rely upon to...

Read full article >

8 Hottest IT Careers of 2014!

Whether it was the Internet Era of 90s or the Big Data Era of today, Information Technology (IT) has given birth to several lucrative career options for many. Though there will not be a “significant" increase in demand for IT professionals in 2014 as compared to 2013, a “steady” demand for IT professionals is rest assured...

Read full article >

Find C Language Classes near you
C Language Classes in Bangalore
C Language Classes in Hyderabad
C Language Classes in Delhi
C Language Classes in Pune
C Language Classes in Mumbai
C Language Classes in Chennai
C Language Classes in Kolkata
C Language Classes in Ghaziabad
C Language Classes in Noida
C Language Classes in Jaipur

Looking for C Language Classes?

Learn from the Best Tutors on UrbanPro

Are you a Tutor or Training Institute?

Join UrbanPro Today to find students near you