@FrodoH - I believe a POSIX pthreads implementation must support mutexes to be POSIX compliant, but do all embedded system vendors implement? Unsure. (Your mileage may vary...) Do your homework to be sure the selected vendor's product supports your requirements.
i have always wanted some plug in to the IDE or even an external piece of application that draws all the dependencies into different types of graphs, but there seem to be little thats free to use out there, do any of you use such a tool?
micgil2293: Drivers are part of the code that is not reusable if the hardware changes. However, the driver API's should be set up so that if the hardware changes, only the driver code has to be updated; the application code can remain relatively unchanged.
A big problem using global variables is a lack of control over assignment of values that are outside limits. If an out of bounds value is detected, it can be difficult to identify the culprit. Also multiple variables for one purpose can be written by multiple sections, with the result that the resulting operation is not correct for any.
George Mallard: Global variables are bad because they can make reading another person's code difficult and can make debugging hard; it can be hard to track down every location where a global variable is changed. They also tend to lead to spaghetti code.
I like to understand every line of code but its not really necessary. The more your know about the program the easier it can be to debug, but in order to use the code properly it isnt necessary to know exactly what every line does.
@George Mallard, my experience is that you might inadvertently access a variable that was set in another module or a library. Also, it is hard to debug if you have to search many modules to figure out where a var got set.
Agree with others - the goal of reusable code is admirable, but may be difficult to achieve, particularly as hardware advances outpace product development/product lifecycles. (ie. - Marketing: What's the newest "thingy" available? We want that in our product. Engineering: We'd have to start all over to use it!)
On large projects it would be impossible to understand every line of code. You just need to understand the API's of the modules you interact with and only learn the details of other code if wierd behaviour occurs.
You don't need to understand EVERY line of code; that would take "forever" to be able to do anything. You don't need to understand internal combustion to drive a car or change the oil. You don't need to understand EVERY transistor in an I.C. to use it in a circuit.
You need to understand the major components and how they interface. To work within a component, more detailed understanding is required.
@Jacob Exactly what percent of code would you expect to be reusable? In my experience (outside of software that spans a specific product family which is actually a single code base) very little code is reusable due to changes in hardware and feature set requirements.
Feature creep - absolutely. And it is not just a technical problem but a "managing your manager" problem. Management wants you to be agile but unless you manage them they will abuse that agility to ruin your life with feature creep and indecision.
You have to be sure that your chosen platform can support feature creep without making you scrap the board or operating system. Be sure your vendor can upgrade the chip without invalidating your development to date.
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