Why is my code resulting in a segmentation fault? - c

Question

The tasks are the following:
/* LAB 6 TASK A*/
/*
Save the entire array ia into a file called 'filename' in a binary
file format that can be loaded by intarr_load_binary(). Returns
zero on success, or a non-zero error code on failure. Arrays of
length 0 should produce an output file containing an empty array.
*/
/* LAB 6 TASK B*/
/*
Load a new array from the file called 'filename', that was
previously saved using intarr_save_binary(). Returns a pointer to a
newly-allocated intarr_t on success, or NULL on failure.
*/
For A, my code is the following:
int intarr_save_binary( intarr_t* ia, const char* filename )
{
int returnValue = 0;
unsigned int len = ia->len;
FILE *f;
if( NULL == (f = fopen (filename, "wb") ))
{
perror( "fopen failed" );
returnValue = 1;
}
else if ( fwrite ( &len, sizeof(int), 1, f) == 1 )
{ // then write of length successful
if (fwrite (ia->data, sizeof(int), len, f) == len)
{
returnValue = 0; // indicate success
}
else
{ // else, write of data failed
returnValue = 3;
}
}
else
{ // else, failed to write len value to file
returnValue = 4;
}
fclose( f ); // cleanup (writes last buffer to file)
return( returnValue );
}
And for B, my code is the following:
intarr_t* intarr_load_binary( const char* filename )
{
unsigned int len = 0;
FILE *f = NULL;
intarr_t* newia = NULL;
if( NULL == fopen (filename, "rb") )
{ // then, fopen failed
perror( "fopen failed" );
exit( EXIT_FAILURE );
} // end if
// implied else, fopen successful
if( NULL == (newia = malloc (sizeof(intarr_t)))){
perror( "malloc failed" );
fclose(f);
exit( EXIT_FAILURE );
} // end if
// implied else, malloc successful
if( (fread (&len, sizeof(int), 1, f) != 1 ) )
{ // then fread failed
perror( "fread failed" );
fclose(f);
free( newia );
exit( EXIT_FAILURE );
} // end if
// implied else, fread for len successful
newia->len = len;
if( NULL == (newia->data = malloc (len*sizeof(int)) ) )
{ // then malloc failed
perror( "malloc failed" );
fclose(f);
free( newia );
exit( EXIT_FAILURE );
} // end if
// implied else, malloc successful
if( fread( newia->data, sizeof(int), len, f ) != len )
{ // then, fread failed
perror( "fread failed" );
fclose(f);
free(newia->data);
free(newia);
exit( EXIT_FAILURE );
} // end if
// implied else, fread successful
fclose (f);
return newia;
} // end function: intarr_load_binary
Can anyone please tell me why my code results in a segmentation fault? Thank you very much.

Answer 1

In the code for B, NULL is passed to fread() in the line
if( (fread (&len, sizeof(int), 1, f) != 1 ) )
so it may lead to Segmentation Fault.
To fix this, assign the file pointer returned from fopen() to f:
Change
if( NULL == fopen (filename, "rb") )
to
if( NULL == (f = fopen (filename, "rb")) )
Also check if the parameters passed to the functions are valid.