Your ld.so contains:

Entry point address: 0x1d780

EDIT: …with which I meant, modulo brainfart: My libc.so.6 contains a proper entry address, while other libraries are pointing at 0x0 and coredump when executed. libc.so is a linker script, presumably because GNU compulsively overcomplicates everything.

…I guess that’s enough for the kernel. It might be a linux-only thing, maybe even unintended and well linux doesn’t break userspace.

Speaking of, I was playing it a bit fast and loose: _start is merely the default symbol name for the entry label, I’m sure nasm and/or ld have ways to set it to something different.

Did you know that main is usually a function?

Unlikely as many Germanic languages have it, with similar meanings. It’s a variant of “ja”, yes. Add a bit of laconicy and you can make “Well.” a sentence in itself.

How does executing a program actually work?

Way too long an answer for a lemmy post

It has an executable flag, but what actually happens in the OS when it encounters a file with an executable file?

Depends on OS. Linux will look at the first bytes of the file, either see (ASCII) #! (called a shebang) or ELF magic, then call the appropriate interpreter with the executable as an argument. When executing e.g. python, it’s going to call /usr/bin/env with parameters python and the file name because the shebang was #!/usr/bin/env python.

How does it know to execute “main”?

Compiled C programs are ELF so it will go through the ELF header, figure out which ld.so to use, then start that so that it will find all the libraries, resolve all dynamic symbols, then do some bookkeeping, and jump to _start. That is, it doesn’t: main is a C thing.

Is it possible to have a library that can be called and also executed like a program?

Absolutely. ld.so is an example of that.. Actually, wait, I’m not so sure any more, I’m getting things mixed up with libdl.so. In any case ld.so is an executable with a file extension that makes it look like a library.

EDIT: It does work. My (GNU) libc spits out version info when executed as an executable.

If you want to start looking at the innards like that I would suggest starting here: Hello world in assembly. Note the absence of a main function, the symbol the kernel actually invokes is _start, the setup necessary to call a C main is done by libc.so. Don’t try to understand GNU’s libc it’s full of hystarical raisins I would suggest musl.

Pure SQL, as in relational algebra, is LOGSPACE/PTIME. Datalog is PTIME-complete when the program (“query”) is fixed, EXPTIME-hard otherwise.

It’s all quite tractable, but there’s definitely turing-complete declerative langugages. Not just pretty much every functional language, but also the likes of prolog.

Functional is also declarative because control flow is implicit/unspecified.

What’s actually missing is logic programming, of which the likes of SQL are a subset.

It’s fine memes are permitted to make jokes and it’s more of a paradigm than vibe coding.

The one paradigm that’s actually missing is logic programming, I would’ve gotten rid of unstructured to include it. The whole paradigm thing really only started with Dijkstra’s rant about unstructured gotos (not the ones C has, in C you can’t jump to the middle of another function).

Not reliably, no. Python is too dynamic to do that kind of thing without solving general program equivalence which is undecidable.

Use a static language, problem solved.