Ah, I read too quickly, didn't notice/realize the length(...)
subexpression was the variable part.
If you don't have alloca, and you don't want to use assembler, and you
don't want the overhead of malloc/free, and you don't want to, or literally
can't, risk demons flying out of your nose:
It seems that any is a typedef for a variable length array, which C
compilers often refuse to support. Some C compilers are more permissive
regarding variable length arrays; gcc, for example, is more permissive.
Emscripten (or clang/llvm) is, apparently, not.
The normal thing to do, when
