I’m curious how software can be created and evolve over time. I’m afraid that at some point, we’ll realize there are issues with the software we’re using that can only be remedied by massive changes or a complete rewrite.
Are there any instances of this happening? Where something is designed with a flaw that doesn’t get realized until much later, necessitating scrapping the whole thing and starting from scratch?
I would say the whole set of C based assumptions underlying most modern software, specifically errors being just an integer constant that is translated into a text so it has no details about the operation tried (who tried to do what to which object and why did that fail).
You have stderr to throw errors into. And the constants are just error codes, like HTTP error codes. Without it how computer would know if the program executed correctly.
stderr is useless if the syscall already returns a single integer only because of stupid C conventions.
You throw an exception like a gentleman. But C doesn’t support them. So you need to abuse the return type to also indicate “success” as well as a potential value the caller wanted.
Exceptionss are bad coding, and what’s abusive of using the full range of an integer? 0 success, everything else, error - check the API for details or call
strerror.Returning error codes in-band is the reason for a significant percentage of C bugs and security holes when the return value is used without checking. Something like Rust’s Result type that forces you to distinguish the two cases is much better design here. And no, you are not working with a whole language ecosystem of “sufficiently disciplined programmers” so that nobody ever forgets to check a return value.
Not to mention that errno is just a very broken design in the times of modern thread and event systems, signals, interrupts and all kinds of other ways to produce race conditions and overwrite the errno value before it is checked.
errno is not shared between threads. Also:
There does not add more race conditions because signal handlers execute in one of regular threads. In single-threaded program signals are functions that can be called by OS at any point of execution, but they do not execute at same time with threads.
errno is bad programming.
You don’t need to.
Returnung structs, returning by pointer, signals, error flags, setjmp/longjmp, using cxa for exceptions(lol, now THIS is real abuse).
Assembly doesn’t have concept of objects.
It does very much have the concept of objects as in subject, verb, object of operations implemented in assembly.
As in who (user foo) tried to do what (open/read/write/delete/…) to which object (e.g. which socket, which file, which Linux namespace, which memory mapping,…).
Indeed. Assembly is(can be) used to implement them.
Kernel implements it in software(except memory mappings, it is implemented in MMU). There are no sockets, files and namespaces in ISA.
You were the one who brought up assembly.
And stop acting like you don’t know what I am talking about. Syscalls implement operations that are called by someone who has certain permissions and operate on various kinds of objects. Nobody who wants to debug why that call returned “Permission denied” or “File does not exist” without any detail cares that there is hardware several layers of abstraction deeper down that doesn’t know anything about those concepts. Nothing in the hardware forces people to make APIs with bad error reporting.
And why “Permission denied” is bad reporting?
Because if a program dies and just prints strerror(errno) it just gives me “Permission denied” without any detail on which operation had permissions denied to do what. So basically I have not enough information to fix the issue or in many cases even to reproduce it.
It may just not print anything at all. This is logging issue, not “C based assumption”. I wouldn’t be surprised if you will call “403 Forbidden” a “C based assumtion” too.
But since we are talking about local program, competent sysadmin can
straceprogram. It will print arguments and error codes.