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Lab 3: Reading Material

Lab 3 is dedicated to dynamic data structures in C, program debugging via the use of valgrind(1) and patching of binary files.

Dynamic data structures in C

Dynamic data structures in C are usually built using pointers and C structures. Please read chapter Complex types of the wikibook. Memory for dynamic data is allocated and released dynamically, on the heap. C library functions for memory management are described in chapter Memory management.

Patching

A convenient utility for inspecting binary files, called hexedit(1), is installed on the lab computers. Please read the man for the utility and familiarize yourself with hexedit by trying to view and edit a few different files.

Debugging

Please read the man page for valgrind(1), you can focus on the --leak-check, --show-reachable and -v parameters. valgrind can help you detect memory leaks and other types of errors (e.g. illegal access to memory address). For a complete list of error messages and their meaning - http://valgrind.org/docs/manual/mc-manual.html.

Input from stdin or other files

You already know fgets(3) for getting "strings" from files (like stdin). Now you must also learn to use fread( ) (see man fread(3)) to read a pre-specified number of bytes from a file. In order to format printouts, you should be more familiar with printf(3). In order to parse strings efficiently and extract values of different types from them you should use sscanf(3).

Other functions to learn

You should also be familiar with memcmp( ). Optionally (for bonus tasks), look up fseek( ) and fwrite( ).