Did you know that a C program’s main() function is not the first code to be run? Depending on the program and the compiler, there are all kinds of interesting and complex functions that get run before main(), automatically inserted by the compiler and invisible to casual observers. For the past several days I’ve been on a quest to reverse engineer a minimal C program, to see what’s inside the executable file and how it’s put together. I was generally aware that some kind of special initialization happened before main() was called, but knew nothing about the details. As it turned out, understanding what happens before main() proved to be central to explaining large chunks of mystery code that I’d struggled with during my first analysis.
In my previous post, I used dumpbin, OllyDbg, and the IDA disassembler to examine the contents of a Windows executable file created from an 18 line C program. This example program is a text console application that only references printf, scanf, and strlen. The C functions compile into 120 bytes of x86 code. Yet dumpbin revealed that the executable file contained 2234 bytes of code, and imported 38 different functions from DLLs. It also located over 1300 bytes of unknown data and constants. The implementations of printf etc were in a C runtime library DLL, so that couldn’t explain the unexpected code bloat. Something else was at work.
Adafruit publishes a wide range of writing and video content, including interviews and reporting on the maker market and the wider technology world. Our standards page is intended as a guide to best practices that Adafruit uses, as well as an outline of the ethical standards Adafruit aspires to. While Adafruit is not an independent journalistic institution, Adafruit strives to be a fair, informative, and positive voice within the community – check it out here: adafruit.com/editorialstandards
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.
Have an amazing project to share? The Electronics Show and Tell is every Wednesday at 7:30pm ET! To join, head over to YouTube and check out the show’s live chat and our Discord!
Join us every Wednesday night at 8pm ET for Ask an Engineer!
Join over 38,000+ makers on Adafruit’s Discord channels and be part of the community! http://adafru.it/discord
CircuitPython – The easiest way to program microcontrollers – CircuitPython.org
New Products – Adafruit Industries – Makers, hackers, artists, designers and engineers! — New Products 11/06/24 Feat Adafruit Pixel Shifter – For Addressable LEDs
Python for Microcontrollers – Adafruit Daily — Python on Microcontrollers Newsletter: MicroPython v1.24.0 is here, a Halloween Wrap-up and Much More! #CircuitPython #Python #micropython @ThePSF @Raspberry_Pi
EYE on NPI – Adafruit Daily — EYE on NPI Maxim’s Himalaya uSLIC Step-Down Power Module #EyeOnNPI @maximintegrated @digikey
Adafruit IoT Monthly — Halloween, WiLo, and more!
Maker Business – Adafruit Daily — First Solar’s $1.1 billion development of vertically integrated factory in the U.S.
Electronics – Adafruit Daily — Oscilloscope Jumble
No Comments
No comments yet.
Sorry, the comment form is closed at this time.