47.Data Structures. Queues

spatlou

All queries, discussions, updates and clarifications related to Project.001; Session.47.Data Structures. Queues

should be posted here.

rajsaw9973

when i use function pointer i am getting this error

[root@localhost 1.00]# ls

clearQueue.c declerations.h destroyQueue.o enQueue.o init.c Makefile

clearQueue.o deQueue.c displayQueue.c exitFunc.c main.c peek.c

creatQueue.c deQueue.o displayQueue.o exitFunc.o mainMenu.c peek.o

creatQueue.o destroyQueue.c enQueue.c headers.h mainMenu.o

[root@localhost 1.00]# make

gcc -o Queue mainMenu.o exitFunc.o creatQueue.o enQueue.o deQueue.o displayQueue.o clearQueue.o peek.o destroyQueue.o

/usr/bin/ld: /usr/lib/gcc/x86_64-redhat-linux/10/../../../../lib64/crt1.o: in function `_start':

(.text+0x24): undefined reference to `main'

/usr/bin/ld: mainMenu.o: in function `mainMenu':

mainMenu.c:(.text+0x9d): undefined reference to `fptr'

/usr/bin/ld: mainMenu.c:(.text+0xb6): undefined reference to `fptr'

/usr/bin/ld: creatQueue.o: in function `creatQueue':

creatQueue.c:(.text+0x50): undefined reference to `fptr'

/usr/bin/ld: creatQueue.c:(.text+0xb7): undefined reference to `fptr'

collect2: error: ld returned 1 exit status

make: *** [Makefile:4: Queue] Error 1

[root@localhost 1.00]#

rajsaw9973

rajsaw9973

decleration

typedef struct

{

int *queue;

unsigned int size;

int f,r;

}Queue;

int init();

extern void* mainMenu(void*);

extern void* exitFunc(void*);

extern void* creatQueue(void*);

extern void* enQueue(void*);

extern void* deQueue(void*);

extern void* displayQueue(void*);

extern void* clearQueue(void*);

extern void* peek(void*);

extern void* destroyQueue(void*);

extern void* (*fptr[9])(void*);

~

jyotipandey9813

void* mainMenu(void*);

.

void* destroyQueue(void*);

void* (*fptr[9])(void*);

“Undefined Reference” error occurs when we have a reference to object name but the linker cannot find the definition of a linked object,

so

Make sure these above function_declarations should be defined in your init.c file or main.c file

deepak4u106

jyotipandey9813

You have to use extern storage class while declaring the functions

jyotipandey9813

@deepak4u106

he already used "extern storage class" during declaring the function in declaration.h

but for allocating them memory he has to define this functions without extern in main.c or init.c .

deepak4u106

@jyotipandey9813

Yes after defining the function in init.c he has to call the function in main.c

47.Data Structures. Queues

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