Questions 4

1. Will these functions leak memory?

   void stat(){
   	double a[500];
   }
   
   void vla(size_t n){
   	double a[n];
   }
   
   void mal(){
   	double* a=(double*)malloc(500*sizeof(double));
   }
   
   void maf(){
   	double* a=(double*)malloc(500*sizeof(double));
   	free(a);
   }
   
   double* mar(){
   	double* a=(double*)malloc(500*sizeof(double));
   	return a;
   }
   

2. Which lines, if any, of the following program will lead to compilation error?

   struct vector {double x,y,z;};
   struct vector v = {1,2,3};
   struct vector x = {1,2,3};
   struct vector a = [1,2,3];
   struct vector u = {.x=1,.y=2,.z=3};
   struct vector w = {.z=3,.y=2,.x=1};
   vector y;
   typedef struct vector vector;
   vector z;
   

3. Which of the following Bash commands creates a list of '.c'-files in the current directory? Hint: redirection.

   ls *.c > cfiles.txt
   ls *.c 1> cfiles.txt
   ls *.c 2> cfiles.txt
   ls *.c &> cfiles.txt
   cat /dev/null > cfiles.txt; for i in *.c; do echo $i >> cfiles.txt; done
   

4. Where does the following main function get its parameter from? That is, who calls the main-function and with which parameters?

   int main(int argc, char* argv[]) { /* do stuff */ }
   

5. How can you convert a parameter of the main function into double or int number?
6. What will the following program print?

   #include<stdio.h>
   #include<stdlib.h>
   double* foo(){ static double a[]={0,0,0}; return a; }
   int main(){
     double* a=foo(); a[2]=1;
     double* b=foo(); b[2]=2;
     printf("a[2] = %g\n",a[2]);
   return EXIT_SUCCESS;}
   

7. What will the following program print?

   #include<stdio.h>
   #include<stdlib.h>
   double* foo(){ double* a=(double*)malloc(3*sizeof(double)); return a; }
   int main(){
     double* a=foo(); a[2]=1;
     double* b=foo(); b[2]=2;
     printf("a[2] = %g\n",a[2]);
     free(a);a=NULL;
     free(b);b=NULL;
   return EXIT_SUCCESS;}
   

8. Can a C-structure contain a function? A pointer to a function?
9. Which of the following lines is the correct declaration and why?

   struct f { int n; double *f(double); };
   struct g { int n; double (*f)(double); };
   

10. Which of the two declarations is valid?

    #include<math.h>
    double (*f)(double) = sin;
    double (*g)(double) = &sin;
    

11. With "f" from the (valid) declaration above, which of the following statements is valid?

    double y = f(1);
    double y = (*f)(1);
    

12. What is the return value of the malloc function from stdlib.h?