CS120 Day 5: Arrays & Pointers; gprof, gcov
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- memory usage
    - registers
    - the "stack"
    - name table
    - the "heap"

	-automatic memory (arrays) are lost after a function return
		-dynamic memory is not lost

	-an array is a pointer except sizeof(array) actually works

	int * ptr = 0;

- pointer variable is one that contains a memory address
	declaration: sometype * valptr
	creates variable valptr which is pointer to a location of sometype
	can be initialized to 0 or NULL (preferred, if #include <stdlib.h>)

- & address operator - returns address of whatever follows
- * indirection or dereferencing operator - returns value being pointed to
- both have unary precedence (one less than () and [])

- can be used to simulate call by reference - pass variable with &
	to pass pointer to location, then use *var to get value
	- must use * as part of function prototype and definition parameter
	- swap example

void swap(int * a, int * b)
{
	int temp = *a;
	*a = *b;
	*b = temp;
}

git clone http://bitbucket.org/menohack/intermediate
>>>> swap.c full example <<<<

>>>> pointers.c sample code <<<<

- pointers and arrays
	- can use almost interchangeably
		aptr = a;
		aptr = &a[0];
		(a == &a[0])
		a[3] == * (aptr + 3)  /* parentheses necessary */
			3 is called the offset
		&a[3] == aptr + 3
	
- pointer arithmetic
	+, -, +=, -= for other pointers or integers
		- makes sense mostly for array subscripts
		- adds a unit the size of the ptr data type for each
		- ie, for each int unit added or subtracted, it goes one
			more or less memory location of that type
	= assignment works for pts of same types
	==, etc. makes sense to compare ptrs within array, and compare to NULL

- arrays of pointers
	- common use is array of strings
	- each string is pointer to a string array
	eg: char *suit[4] = {"Hearts", "Diamonds", "Clubs", "Spades"}

- pointers to pointers
	- used to change value of pointer parameter
- when passing to functions, if want pointer to change, must pass
	address of pointer (pointer to pointer)
- go over this concept really well 


gprof

	-profiling - measuring the running time of each function
		-useful for optimization--improving the slowest function is the best option
	-add -pg compiler option to gcc
	-then run the executable to produce gmon.out
	-gprof executablename to show information

gcov

	-test coverage - determines which lines of code were actually executed
		-good tests have 100% coverage of your code
	-add -fprofile-arcs -ftest-coverage options to gcc
	-turn off optimizations with -O0 (oh zero) or it can skip code
	-run the executable to produce .gcda file
	-"gcov <c files>" to list coverage for each source file
		-produces filename.c.gcov for each source file
		-.c.gcov files contain the number of times each line was executed


========== didn't get to this stuff ======================

- command line arguments
	main(int argc, char *argv[])
		argc is count of arguments, including program name
		argv[0] is program name
		argv[i] is ith argument

- const can be applied to any variable, in declaration or parameter list
	- added to ANSI C (not originally part of C)
	- should be used to protect data
	- as you write program, ask if variable should be modified -
		if not, then use const
	- for const variable: const int i
	- to make const pointer must say: int * const iptr = &i
		- must be initialized when declared (with = or as parameter)
		- eg: array is const ptr: *myarray ~ myarray[]
	- const ptr to const data: const int * const iptr
- in general: read declarations from right to left to get it straight