Old BASIC programmers are mostly working on Pick and other "business BASIC" systems, and I still run into them from time to time. But most of that code is only useful within a single business, so I expect it to eventually die out. (Meanwhile, new BASIC programmers are proliferating in the retrocomputing hobby.)
By contrast, on my system here I have over a thousand libraries written in C or C++. A random sampling reveals libraries for: LevelDB; various JS interpreters; file format handlers for zipfiles, OpenEXR, DjVu, and JPEG; gamepad interaction; a sparse matrix solver (used in Octave); the RIST protocol (used by OBS Studio); simulation with finite element models, which uses a different sparse matrix solver (used by FreeCAD); inspecting and manipulating configuration of PCI devices; the MTP protocol; the Icecast protocol; the protocol FTDI devices speak over USB; and so on.
Nearly all software written today is either written in C, written in C++, or interpreted or compiled by an interpreter or compiler written in C or C++.
No. I'm saying they will behave subtly different. One will not stop other might, etc.
It's kinda like running same code in debug and release mode and expect identical results.
> Old BASIC programmers are mostly working on Pick and other "business BASIC" systems
I've never heard of those things either. Nor have I met a programmer outside retro computing groups that used BASIC.
> Nearly all software written today is either written in C, written in C++, or interpreted or compiled by an interpreter or compiler written in C or C++.
For time being. Up until 10 years you had no other realistic options.
Its being not essential doesn't matter. If you have a Fil-C code that terminates on UB and a C code that doesn't, you have two provably semantically (subtly) different programs.
Proof: You have a program that halts on UB and one that continues running on UB.
> I think there are more C programmers today than there have ever been, and I doubt that that number will ever fall to zero while there are still humans.
Think that depends on more things than just there being humans. Where my BASIC programmers at?