Q:
CAN A POINTER BE FREED MORE THAN ONCE IN C? WHAT HAPPENS IF DO SO? OR CAN A POINTER BE FREED TWICE IN C?
belongs to collection: C INTERVIEW QUESTIONS AND ANSWERS
C INTERVIEW QUESTIONS AND ANSWERS
- WHAT IS C LANGUAGE?
- WHO DEVELOPED C LANGUAGE?
- DESCRIBE ABOUT HISTORY OF C PROGRAMMING LANGUAGE
- WHERE IS C PROGRAMMING LANGUAGE USED OR USES OF C LANGUAGE?
- WHAT IS THE DIFFERENCE BETWEEN C AND C++?
- WHAT IS THE DIFFERENCE BETWEEN TOP DOWN APPROACH AND BOTTOM UP APPROACH IN PROGRAMMING LANGUAGES?
- WHAT IS THE DIFFERENCE BETWEEN C AND JAVA?
- C LANGUAGE HAS BEEN DEVELOPED IN WHICH LANGUAGE?
- WHICH YEAR C LANGUAGE IS DEVELOPED?
- WHAT IS MEANT BY PROGRAMMING LANGUAGE AND GIVE SOME EXAMPLES?
- DESCRIBE ABOUT C STANDARDS
- WHAT ARE THE KEY FEATURES OR CHARACTERISTICS OF C LANGUAGE?
- WHAT IS EMBEDDED C?
- WHICH LEVEL IS C LANGUAGE BELONGING TO?
- WHAT DO YOU MEAN BY HIGH LEVEL, MIDDLE LEVEL AND LOW LEVEL LANGUAGES AND GIVE AN EXAMPLE FOR EACH?
- WHAT IS THE DIFFERENCE BETWEEN STRUCTURED ORIENTED, OBJECT ORIENTED AND NON-STRUCTURE ORIENTED PROGRAMMING LANGUAGE?
- WHAT IS COMPILER?
- WHAT IS THE DIFFERENCE BETWEEN ASSEMBLER, COMPILER AND INTERPRETER?
- WHAT IS PRINTF()?
- WHAT IS SCANF()?
- WHAT IS MEANT BY PROTOCOL?
- EXECUTION OF A C PROGRAM STARTS FROM WHICH FUNCTION?
- WHAT ARE ALL THE SECTIONS THAT A C PROGRAM MAY/MUST HAVE?
- WHAT IS IDE?
- LIST OUT SOME OF C COMPILERS
- WHAT IS HEADER FILE IN C LANGUAGE?
- IS C LANGUAGE CASE SENSITIVE?
- WHAT IS MACRO? WHY DO WE USE MACRO?
- WHAT IS DATA TYPE IN C?
- WHAT IS THE DIFFERENCE BETWEEN INT, CHAR, FLOAT & DOUBLE DATA TYPES?
- WHAT IS THE USE OF SIZEOF() FUNCTION IN C?
- WHAT IS MODIFIER IN C?
- WHAT ARE DIFFERENT TYPES OF MODIFIERS IN C?
- WHAT IS ENUM IN C?
- WHAT IS VOID IN C?
- WHAT IS TOKEN IN C?
- WHAT ARE THE TYPES OF C TOKENS?
- WHAT IS IDENTIFIER IN C?
- WHAT IS KEYWORD IN C?
- LIST OUT SOME KEYWORDS AVAILABLE IN C LANGUAGE
- WHAT IS CONSTANT IN C?
- WHAT ARE THE TYPES OF CONSTANTS IN C?
- WHAT IS VARIABLE IN C?
- WHAT IS THE DIFFERENCE BETWEEN CONSTANT AND VARIABLE IN C?
- CAN VARIABLE NAME START WITH NUMBERS?
- WHAT IS THE DIFFERENCE BETWEEN VARIABLE DECLARATION AND VARIABLE DEFINITION IN C?
- WHAT ARE THE DIFFERENT TYPES OF VARIABLE IN C?
- WHAT IS LOCAL VARIABLE IN C?
- WHAT IS GLOBAL VARIABLE IN C?
- WHAT IS ENVIRONMENT VARIABLE IN C?
- WHAT IS OPERATOR IN C?
- WHAT ARE THE DIFFERENT TYPES OF OPERATORS IN C?
- WHAT IS THE SYNTAX FOR TERNARY OPERATOR IN C?
- WHAT IS ARITHMETIC OPERATOR IN C?
- WHAT IS ASSIGNMENT OPERATOR IN C?
- WHAT IS THE RELATIONAL OPERATOR IN C?
- WHAT IS THE LOGICAL OPERATOR IN C?
- WHAT IS BITWISE OPERATOR IN C?
- WHAT ARE ALL DECISION CONTROL STATEMENTS IN C?
- WHAT ARE ALL LOOP CONTROL STATEMENTS IN C?
- WHAT IS THE DIFFERENCE BETWEEN WHILE AND DO-WHILE LOOPS IN C?
- WHAT IS THE DIFFERENCE BETWEEN SINGLE EQUAL “=” AND DOUBLE EQUAL “==” OPERATORS IN C?
- WHAT IS THE DIFFERENCE BETWEEN PRE INCREMENT OPERATOR AND POST INCREMENT OPERATOR IN C?
- WHAT IS THE DIFFERENCE BETWEEN PRE DECREMENT OPERATOR AND POST DECREMENT OPERATOR?
- WHAT IS “&” AND “*” OPERATORS IN C?
- WHAT WILL HAPPEN IF BREAK STATEMENT IS NOT USED IN SWITCH CASE IN C?
- WHY IS DEFAULT STATEMENT USED IN SWITCH CASE IN C?
- WHAT IS THE USE OF “GOTO” STATEMENT?
- WHAT VALUE IS ASSIGNED TO THE BELOW VARIABLES?
- WHAT IS THE DIFFERENCE BETWEEN AUTO VARIABLE AND REGISTER VARIABLE IN C?
- WHAT IS THE DIFFERENCE BETWEEN AUTO VARIABLE AND STATIC VARIABLE IN C?
- WHERE SHOULD TYPE CAST FUNCTION NOT BE USED IN C?
- HOW MANY ARGUMENTS CAN BE PASSED TO A FUNCTION IN C?
- WHAT IS STATIC FUNCTION IN C?
- IF YOU WANT TO EXECUTE C PROGRAM EVEN AFTER MAIN FUNCTION IS TERMINATED, WHICH FUNCTION CAN BE USED?
- WHAT IS EXIT() FUNCTION IN C?
- WHAT IS THE DIFFERENCE BETWEEN EXIT() AND RETURN() IN C?
- WHAT IS THE USE OF “#DEFINE” IN C?
- WHAT IS THE SYNTAX FOR COMMENTS IN C?
- HOW WILL YOU OVERRIDE AN EXISTING MACRO IN C?
- HOW TO CHECK WHETHER MACRO IS DEFINED OR NOT IN A C PROGRAM?
- WHAT IS THE DIFFERENCE BETWEEN MEMCPY() & STRCPY() FUNCTIONS IN C?
- WHAT IS THE DIFFERENCE BETWEEN MEMCPY() & MEMMOVE() FUNCTIONS IN C?
- IS THERE ANY INBUILT LIBRARY FUNCTION IN C TO REMOVE LEADING AND TRAILING SPACES FROM A STRING? HOW WILL YOU REMOVE THEM IN C?
- WHAT IS THE DIFFERENCE BETWEEN STRCPY() & STRNCPY() FUNCTIONS IN C?
- CAN ARRAY SUBSCRIPTS HAVE NEGATIVE VALUE IN C?
- WHAT IS THE DIFFERENCE BETWEEN ARRAY AND STRING IN C?
- WHAT IS POINTER IN C?
- WHAT IS NULL POINTER IN C?
- WHAT IS NULL IN C?
- WHAT IS VOID POINTER IN C?
- WHAT IS DANGLING POINTER IN C?
- WHAT IS WILD POINTER IN C?
- WHAT IS FILE POINTER IN C?
- WHEN CAN VOID POINTER AND NULL POINTER BE USED IN C?
- WHAT IS CONST POINTER IN C?
- IS POINTER ARITHMETIC A VALID ONE? WHICH ARITHMETIC OPERATION IS NOT VALID IN POINTER? WHY?
- IS VOID POINTER ARITHMETIC A VALID ONE? WHY?
- WHAT IS THE DIFFERENCE BETWEEN NULL AND ZERO?
- WHAT IS THE DIFFERENCE BETWEEN NULL POINTER AND UNINITIALIZED POINTER IN C?
- CAN ARRAY SIZE BE DECLARED AT RUN TIME?
- WHAT IS MEMORY LEAK IN C?
- WHAT HAPPENS WHEN WE TRY TO ACCESS NULL POINTER IN C?
- WHAT IS MEANT BY SEGMENTATION FAULT OR MEMORY FAULT IN C?
- WHAT IS MEANT BY CORE DUMP IN C?
- CAN A POINTER BE FREED MORE THAN ONCE IN C? WHAT HAPPENS IF DO SO? OR CAN A POINTER BE FREED TWICE IN C?
- WHAT IS THE SIZE OF INT POINTER AND CHAR POINTER IN C?
- HOW WILL YOU PRINT THE VALUE AND ADDRESS OF A POINTER VARIABLE (EXAMPLE INT *P) IN C?
- HOW WILL YOU PRINT THE VALUE AND ADDRESS OF A NORMAL VARIABLE IN (EXAMPLE INT P) C?
- WHAT ARE LIBRARY FUNCTIONS AND THEIR USE IN C LANGUAGE? CAN WE WRITE OUR OWN FUNCTIONS AND INCLUDE THEM IN C LIBRARY?
- CAN VARIABLE NAME BE START WITH UNDERSCORE IN C?
- CAN VARIABLE NAME HAVE SPECIAL SYMBOLS IN C?
- WHAT IS INLINE FUNCTION IN C?
- IS IT POSSIBLE TO PRINT “HELLO WORLD” WITHOUT SEMICOLON IN C? HOW?
- WHAT IS THE SCOPE OF LOCAL, GLOBAL AND ENVIRONMENT VARIABLES IN C?
- WHY ARE WE USING POINTERS IN C?
- WHAT IS STATIC VARIABLE IN C?
- WHAT IS EXTERN AND STATIC FUNCTION IN C?
- WHAT IS THE DIFFERENCE BETWEEN POINTER AND ARRAY IN C?
- WHAT IS THE USE OF MAIN() FUNCTION IN C?
C programming
1st scenario: After freeing a pointer in a C program, freed memory might be reallocated by some other or same program luckily. In this scenario, freeing the same pointer twice won’t cause any issue.
2nd scenario: We can free a pointer. Then, we can allocate memory for same pointer variable. Then, we can use it and free it again. This is also not an issue.
3rd scenario: If we free the same pointer second time without reallocating memory to that pointer, then what happens? As per ANSI/ISO C standard, this is undefined behaviour. This undefined behaviour may cause anything to the program that we do not expect to happen.
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