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[[Category:SPO600 Labs]] {{Admon/lab|Purpose of this Lab|In this lab, you will investigate the relationship between basic C source code and the output of the C compiler.}}<!-- {{Admon/tip|IrelandHost System|Perform You can choose to perform this lab on ireland.proximity.on.ca -- an account has been created for each any of the [[SPO600Servers]] student. See your professor for login information. Alternately, you may use your own system if it has been set up with development tools and libraries, '''plus ''' the static version of the glibc library.}} {{Admon/important|Winter 2020|In Winter 2020, this lab is not a required lab and will instead be used as an in-->class Demo.}}
== Resources ==
* [[Assembly Language]]
* [[ELF]] file format
* [[X86_64 Register and Instruction Quick Start]]
* [[Aarch64 Register and Instruction Quick Start]]
== Lab 2 / Demo ==
1. Write a basic C program which prints a message on the screen, [http://enwww.wikipediaroesler-ac.orgde/wikiwolfram/Hello_world_program hello.htm Hello World!]-style -- something like this:
#include <stdio.h>
}
2. Compile the program using the GCC compiler. Include each of these compiler options (refer to the gcc manpage for details):
-g # enable debugging information
(ii) Which section contains the string to be printed?
{{Admon/tip|objdump ''vs'' readelf|The output of strings using way that <code>objdump</code> formats strings is not formatted in the best way well suited for some purposesuses. The <code>readelf -p</code> command may be a better tool for viewing some strings.}}
4. Try to gain a basic understanding of what the compiled code is doing. '''Focus on the section marked <main> but also take a look at the other sectionsand the overall file size.'''
5. Recompile the code with these changes:
6. Blog about your results. Important! -- explain what you're doing so that a reader coming across your blog post understands the context (in other words, don't just jump into a discussion of optimization results -- give your post some context).
{{Admon/important|Include Seven Variants|Blog about all seven compilations -- the original and the six variants listed in step (5) -- not the just variant your group examined in class.}}
{{Admon/tip|Make|Learn how to use [[Make and Makefiles|make]] -- your life as a programmer will be much easier, and you'll get back years of your life!}}
== External Resources ==
* For a general overview of ELF, see the Wikipedia article on [http://en.wikipedia.org/wiki/Executable_and_Linkable_Format Executable and Linkable Format]
