Lecture 13 - John Ribeiro - February 21st
- Cannot compare two objects directly
Example:
Vector m; Vector c;
- / Vector here consists of three integers */
if ( m == c ) {
//ERROR!
}
- Exam 1 on 03/01 in class
- Online, open book - File operation, structures, recursion, pointer.. - Make sure to go over all previous notes, exercises, and assignments - Will receive a zero if a segmentation fault, syntax error occurs in grading - Infinite submissions
For Makefile ( which will be given on the exam )
GCC = gcc -g -Wall -Wshadow ipa1: maze.o main .o
$(GCC)
...
This remains the same as in all previous programs
...
test:
./ipa1 maze1 > output1
diff output1 solution1
./ipa1 maze2 > output2
diff output2 solution2
valgrind --leak-check=yes -v ./ipa1 maze
The above test part of Makefile will make it so that ./ipa1-2 exmaze5 (or something to similar effect) will no longer have to be typed. All that has to be included is:
make test
And the above cold will run
- Many problems come from uninitialized variables and pointers, Unpredictable behaviour.
- Use invalid values to guarantee programs fail
- Read your code before testing. Testing won't tell you where the program fails.
- Design your solution on paper before writing code. the sooner you start coding, the later you can finish.
- Read code before testing
Tips && Tricks
- make memory allocation and release symmetric
- have only one place to allocate and release memory
- keep functions short
- do no copy and paste code. Use function instead
- use valgrind, even though program seems to work
typedef struct {
int x; int y; int z;
} Vector;
Vector_construct Vector_destruct Vector_print
The above is how a structure should be divided so that the program and main function can look cleaner and easier to read
BINARY MODE
void vector_writeb ( char * filename, Vector v ) {
fptr = fopen ( filename, "wb"/"rb" );
}
In the above situation, "wb xor "rb" can be used. "wb" means write binary while "rb" means read binary.
fwrite ( address of object, size, number, filepointer )
&v sizeof(Vector) 1 fptr
# of elements in an array
fread operates in the same fashion with exactly the same arguments
- Object with Pointers*
typedef struct {
char *name; int year; int month; int date;
}Person;
Person Person_Constructor ( char * n, int y, int m, int d ) {
Person p; p.name = malloc ( sizeof ( char ) * strnlen ( n ) + 1 ); strcpy ( p.name, n ); p.year = y; p.month = m; p.date = d;
return p;
}
Call stack of above...
Person.name Person.year Person.month Person.date d m y n
void Person_destruct ( Person p ) {
free ( p.name );
}
Main:
Person p = Person_Constructor ( "Alice", 1981, 11, 22 ); Person_destruct ( p );
