I have a 'struct' which I would like to use in multiple sources files. I have declared the struct in the Header File and then have included in the sources files. It would be great if someone can assist me in this problem.
I am posting Header, Source and Error
#ifndef DATABASE_H
#define DATABASE_H
struct dataBase
{
char modelName;
float capacity;
int mileage;
char color;
};
extern struct dataBase Inputs;
#endif /* DATABASE_H */
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include "dataBase.h"
struct dataBase Inputs = NULL;
//size_t Inputs_Size = 0;
int main (void)
#include "hw4_asharma_display.h"
#include <stdio.h>
#include "dataBase.h"
void printLow(int size)
{
// Declaring Variables
int i;
for(i=0; i<size; i++)
{
printf("%s %f %d %s\n",
Inputs[i].modelName,
Inputs[i].capacity,
Inputs[i].mileage,
Inputs[i].color);
}
hw4_asharma_display.c:14:23: error: subscripted value is not an array, pointer, or vector
Inputs[i].modelName,
~~~~~~^~
hw4_asharma_display.c:29:23: error: subscripted value is not an array, pointer, or vector
Inputs[i].modelName,
Inputs is not an array, so you can't just use the [i] index notation. You'll have to change its declaration from:
struct dataBase Inputs = NULL;
(btw the NULL part is pointless) to
struct dataBase Inputs[N];
Instead, if you meant to have only one element, keep the declaration:
struct dataBase Inputs;
but remove the [i] part:
printf("%c %f %d %c\n",
Inputs.modelName,
Inputs.capacity,
Inputs.mileage,
Inputs.color);
Also, you will have to fill each element before printing or you will get all zeroes and blanks.
Related
shm_fileuploader.c:
#include "sharedMemory.h"
struct filesharing_struct temp()
{
printf("Enter the name of the file. ");
scanf("%s", &fname);
}
sharedMemory.h:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <unistd.h>
//void* get();
const int SIZE = 40960;
const char *name = "obaloch_filesharing";
struct filesharing_struct{
char flag;
int size;
char content;
char fname[50];
};
//struct filesharing_struct temp;
I am getting an error saying "error: ‘fname’ undeclared" and im not sure why since fname is declared in my header file. Is there anyway i can use fname in the from the .h file in the .c file?
You need to declare a variable whose type is the structure, and scan into its fname member.
Then you can return the structure from the function, to satisfy the return type.
struct filesharing_struct temp()
{
struct filesharing_struct temp;
printf("Enter the name of the file. ");
scanf("%s", &temp.fname);
return temp;
}
I am trying to create a simple ADT using a structure that takes 2 dates. Then returns an age. It must use a Header file, a source file for the Header file, and a main file.
This is what I have it runs and nothing happens. Can someone tell me what i am doing wrong?
age.h
#ifndef AGE_H_
#define AGE_H_
typedef struct getage * Age;
#define MAX 5
Age get_Age(int birthYear, int yearNow);
void age_Destroy(Age a);
#endif
age.c
#include <stdio.h>
#include "age.h"
struct getage {
int birthYear;
int yearNow;
};
Age a[1];
Age get_Age(int birthYear, int yearNow){
int giveAge = 0;
giveAge = a[0]->yearNow - a[0]->birthYear;
printf("%d",giveAge);
return 0;
}
void age_Destroy(Age a){
free(a);
}
main.c
#include <windows.h>
#include <stdio.h>
#include "age.h"
void age_print(Age a);
void age_print(Age a){
printf("%d\n", &a);
}
int main() {
Age a;
get_Age(1986, 2020);
age_print(a);
printf("%d\n", &a);
system("pause");
//age_Destroy(a);
}
What are wrong:
In the function get_Age:
Instead of allocating structures, a[0] (global variable, initialized to NULL) is dereferenced.
0 (converted to NULL) is returned instead of returning an age.
In the function age_Destroy:
free() is used without declaration nor including proper header.
In the function age_print:
Data having wrong type is passed to printf(): %d requests int but Age* is passed.
In the function main:
The return value of get_Age is dropped.
Data having wrong type is passed to printf(): %d requests int but Age* is passed.
Fixed code that won't cause Segmentation Fault nor undefined behavior:
age.h (not changed)
#ifndef AGE_H_
#define AGE_H_
typedef struct getage * Age;
#define MAX 5
Age get_Age(int birthYear, int yearNow);
void age_Destroy(Age a);
#endif
age.c
#include <stdio.h>
#include <stdlib.h> // for malloc() and free()
#include "age.h"
struct getage {
int birthYear;
int yearNow;
};
Age get_Age(int birthYear, int yearNow){
Age a = malloc(sizeof(*a)); // allocate a structure
if (a == NULL) { perror("malloc"); exit(1); }
a->yearNow = yearNow; // assign data
a->birthYear = birthYear;
int giveAge = 0;
giveAge = a->yearNow - a->birthYear;
printf("%d",giveAge);
return a; // return pointer to the allocated structure
}
void age_Destroy(Age a){
free(a);
}
main.c
#include <stdlib.h> // more portable header for system()
#include <stdio.h>
#include "age.h"
void age_print(Age a);
void age_print(Age a){
printf("%p\n", (void*)a); // use valid combination of format and data
}
int main() {
Age a;
a = get_Age(1986, 2020); // assign the return value
age_print(a);
printf("%p\n", (void*)a); // use valid combination of format and data
system("pause");
age_Destroy(a); // enable freeing
}
(Some behavior may look weird, but I believe this is valid because not desired behavior is described.)
I'm trying to write a data structure with two elements, and then defining a variable of that type struct. However, after initializing the variable in the main function, I'm getting segmentation fault and I don't know why.
#include <stdio.h>
#include <string.h>
struct AnimalSizes {
char stringName[50];
double sizeLength;
} animalSizes[2];
int main()
{
struct AnimalSizes *snakes;
strcpy(snakes[0].stringName,"Anaconda");
snakes[0].sizeLength=3.7;
strcpy(snakes[1].stringName,"Python");
snakes[1].sizeLength= 2.4;
printf("%c", *snakes[0].stringName);
printf("%lf", snakes[0].sizeLength);
printf("%c", *snakes[1].stringName);
printf("%lf", snakes[1].sizeLength);
return 0;
}
You try to strcpy to destination where is no allocated memory. That is undefined behavior.
You should first allocate enough memory to hold two AnimalSizes instances:
struct AnimalSizes *snakes;
snakes = malloc(2 * sizeof(struct AnimalSizes));
Also, here
printf("%c", snakes[0].stringName);
you are trying to output the first character of stringName. I assume, what you rather want to do is to output whole string with %s.
You've declared a pointer to a struct AnimalSizes, and you have declared an array struct AnimalSizes[2], but you have not made the pointer point to this array:
int main()
{
struct AnimalSizes *snakes = &animalSizes[0];
...
}
Alternatively, you may choose to not declare a global variable, rather choosing to allocate memory in main:
#include <stdlib.c>
#include <stdio.h>
#include <string.h>
struct AnimalSizes {
char stringName[50];
double sizeLength;
};
int main()
{
struct AnimalSizes *snakes = (struct AnimalSizes*) malloc(2*sizeof(struct AnimalSizes));
strcpy(snakes[0].stringName,"Anaconda");
snakes[0].sizeLength=3.7;
strcpy(snakes[1].stringName,"Python");
snakes[1].sizeLength= 2.4;
printf("%c", *snakes[0].stringName);
printf("%lf", snakes[0].sizeLength);
printf("%c", *snakes[1].stringName);
printf("%lf", snakes[1].sizeLength);
free(snakes);
return 0;
}
the following proposed code:
eliminates any need for malloc() and free()
performs the desired functionality
separates the definition of the struct from any instance of the struct.
inserts some spacing between the first letter of the snake name and the 'size' of the snake, for readability
applies certain other changes to the code for 'human' readability
and now the proposed code:
#include <stdio.h>
#include <string.h>
struct AnimalSizes
{
char stringName[50];
double sizeLength;
};
int main( void )
{
struct AnimalSizes snakes[2];
strcpy(snakes[0].stringName,"Anaconda");
snakes[0].sizeLength=3.7;
strcpy(snakes[1].stringName,"Python");
snakes[1].sizeLength= 2.4;
printf("%c ", snakes[0].stringName[0]);
printf("%lf\n", snakes[0].sizeLength);
printf("%c ", snakes[1].stringName[0]);
printf("%lf\n", snakes[1].sizeLength);
return 0;
}
a run of the proposed code outputs:
A 3.700000
P 2.400000
I have a header file structs.h as follows:
#include <stdio.h>
typedef struct
{
char *name;
}
student;
In the file structs.c,
#include <stdio.h>
#include "structs.h"
int main()
{
student students[3];
scanf("%s", &students[0].name);
return 0;
}
The scanf statement gives an error since it says %s is of type char* but argument is of type char**. Removing the & gives a segmentation fault.
How else would I write this? It is a array within an array of struct variables but it should be able to take input...
Hi All,
from the above image.
I am able to compile, but the program crashes at runtime.
Please advise me what could be the resolution to solve this?
Thank you
// structArray.h:
#ifndef __STRUCTARRAY_H_
#define __STRUCTARRAY_H_
typedef struct _vector{
int* str;
int maskSize;
// etc...
}__attribute__((__packed__)) _vector_t;
#endif /* _STRUCTARRAY_H_ */
**// do_structArray.c**
#include "structArray.h"
extern struct _vector_t t;
void do_structArray (void) {
int plaintext[2] = {0x05, 0x08};
_vector_t t[] = {
{plaintext, sizeof(plaintext)},
//{},
};
printf("Content: \n%x \n", t[1].str[1]);
}
// main : just calling do_structArray
#include <stdio.h>
#include <stdlib.h>
#include "structArray.h"
extern struct _vector_t t;
int main(int argc, char *argv[]) {
do_structArray();
system("PAUSE");
return 0;
}
You are accessing t[1] but only have one item in t. Try printf("Content: \n%x \n", t[0].str[1]).
Array indices begin from 0 in C. You're accessing an array element past the end of the array. Change the index to 0:
printf("Content: \n%x \n", t[0].str[0]);