CSE13S Lecture 8 & 9

GDB

GNU Project Debugger, a command-line tool used to debug programs by controlling their execution and inspecting their state

cc –g hello.c –o hello

Add the –g option with the cc command to enable debugging

Two debugging tools

GNU Debugger (gdb) – for logical errors

○ Valgrind – for memory errors

Starting up gdb

Simply run gdb passing the executable in the argument

○ Example: gdb ./hello

The GNU Debugger (gdb)

What can you do with gdb?

What is an array?

The size may be determined either at compile time (static memory allocation) or at run

time (dynamic memory allocation).

Static arrays:

declared using static memory allocation technique

○ Size is fixed and specified in the code

○ Memory is allocated at compile time on the

function stack frame

Dynamic arrays:

declared using dynamic

memory allocation technique

○ Size is specified at run-time

○ Memory is allocated at run time from the heap

○ Memory allocated using functions such as

malloc, calloc and realloc from the stdlib.h file

Array initialization:

type array-name[size] = {list of values};

Summary of scope and lifetime of variables

Macros for functions

Example: #define MIN(x, y) ((x) < (y) ? (x) : (y))

 Example: #define MAX(x, y) ((x) > (y) ? (x) : (y))

(condition) ? (expression_if_true) : (expression_if_false)

So it works like:

If condition is true → result = expression_if_true

If condition is false → result = expression_if_false

Passing 2-D arrays to functions

Function must be called by passing only the array name

○ Function declaration and definition must indicate that the array has 2 dimensions by including

2 sets of brackets

○ The size of the second dimension must be specified