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Lecture 10

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Lecture 10, Thu 08/01

The good, bad and ugly about pointers, C++ Memory Model, Dynamic memory allocation (Heap), Heap vs Stack

Code from lecture

https://github.com/ucsb-cs16-m19/code-from-class/tree/master/08-01

Stuff I wrote on the “whiteboard”

Go here and click on the appropriate date: https://1drv.ms/o/s!AlgIeD1urAgmgQU7loNfb3-LYrma

Topics

The good:

• Pointers allow arrays to be passed to functions efficiently
• Pointers allow arrays of large structs to be traversed effiently

The bad:

• Pointers can only point to one type of data (not generic)
• They don’t automatically point - need to do some work

The ugly

• Bugs in code that involves pointers can cause your program to irrecoverably crash (Segmentation fault)
• Examples: dereferencing a null pointer, out of bound array access, dereferncing a pointer that has junk value.

C++ Memory model

• Barebones model of memory: value vs address
• Scope: local vs. global

• Layout of compiled C++ program in memory: text, global data , heap and stack

• A first look at dynamic memory allocation
• The hows and whys of creating data on the stack vs. heap