Comment by guerby
10 hours ago
Ada 83 has no UB on call stack overflow, from the reference manual :
http://archive.adaic.com/standards/83lrm/html/lrm-11-01.html
"STORAGE_ERROR This exception is raised in any of the following situations: (...) or during the execution of a subprogram call, if storage is not sufficient."
So it's just as useful as when your stack area ends with a page that will segfault on access, or your CPU will raise an interrupt if stack pointer goes beyond a particular address?
It's not safe though because throwing an exception, panicking, etc, is still a denial of service. It's just more deterministic than silently overwriting the heap instead. If the program is critical then you need to be able to statically prove the full size of the stack, which you can do with C and C++ with the right tools and restrictions.
You're mixing specification (a language reference manual) and implementation (a given compiler, target, options, ...).
The Ada language specification says the Ada programmer can expect any Ada compiler when used in fully compliant mode to properly raise STORAGE_ERROR when a stack overflow occurs.
Only the Ada compiler writer has to deal with this, not every single programmer on every single program and platform (the UB behaviour of some languages).
In the case of GCC/GNAT the compiler manual provides insight on how to be in compliant mode per target regarding stack overflow, what are the limitations if any. You have tools to monitor and analyze you Ada code in this respect too.
Deterministic, well-defined behavior is inherently safer than undefined behavior. It allows you to diagnose the problem and fix it. UB emphatically does not, and I don't dare to think of how many millions of person-hours are wasted every year dealing with the results.
A segfault is considered safe if you're talking about functional safety because it results in a return to a defined safe state (RTDSS).
If a segfault leads to some other state you do not deem "safe", such as a single program gating access to a valuable asset with a default fail state of "allow", you just have a fundamental design flaw in your system. The safety problem is you or your AI agent, not the segfault.