There are definitely some cases where memory safety isn't especially important:

• Single player games
• Apps that don't process external data (e.g. a simple calculator).
• Lots of things running on microcontrollers, where the form of input could never possibly cause any security issues. E.g. a motor controller or a basic syringe pump or a (non-smart) washing machine or something.
• Tests, e.g. I've considered writing RISC-V tests in Zig. They're traditionally written in C or assembly.

In cases like those, memory unsafety mainly leads to non-security bugs and annoying debugging sessions. But I wouldn't say it's as much of a deal breaker compared to e.g. writing a video codec or font renderer or web browser or DNS server or whatever.

I still think Rust is a better choice than Zig in most cases anyway, even ignoring memory safety. But in these cases it's at least a defensible choice.

in c code you will see malloc, alloc, free w/e scattered through the code base, most static tools lack because they don't control the memory and just analyze address spaces or do static code analysis. they look top down and try to catch errors.

zig's design forces you to create a memory allocator before any object initializations (alloc/free) and is typically constructed at the top level and passed through to functions. this allows you to swap implementation easily and use the allocator to claim memory or return an error to the caller if it can't.

you can do some simple static allocator, general purpose allocator (can grow memory space as you allocate more objects) or in this case to test memory safety a debug allocator which you use in your tests. This moves the memory inspection inside of where your program allocates memory. this is more of an inside out approach where the analysis is produced by controlling the memory allocations and frees through a standard interface.

Yes. It's not as easy and reliable as Zig.

from rust docs:

Note: “Zero-cost” means zero runtime cost, not zero compile cost. The compiler does real work — monomorphization and inlining — to make abstractions disappear, and that work shows up as longer build times. See Reducing Compile Time for the trade-off.

most of the benefits come from a shared code base, one compiler (which is insanely fast with incremental rebuilds and can watch files for changes) means changes in the c code reflect in a single build step within seconds. the benefit is primarily for the developer as the compiler output should be relatively similar.