[bionsuba]

There are many parts of the std lib that assume GC usage. When you mark a function as @nogc, DMD does a compile-time check and will not compile your program if there's a GC call. Applying this to main means that your entire program will by necessity be GC free.

[Rusky]

Right, I understand that it effectively eliminates GC usage, I'm just wondering how much of an impact that has on what tools you have. In the extreme, I can imagine it degenerating into basically writing C, for example.

[bionsuba]

You have access to all of std.range and std.algorithm, most of std.datetime, many functions in std.string and std.digest, and others scattered throughout the std lib. The main thing you'll want to look at is std.experimental.allocator, which has tons of tools for manual memory allocation.

Most of the community packages out there use the GC. Some though are transitioning to a std.experimental.allocator interface, like this containers library https://github.com/economicmodeling/containers

[kaleidic]

See Sociomantic 's Ocean library. But you don't need to go that far in practice in most uses. If you keep GC heap small, disable the GC in critical code paths, have threads that the GC doesn't get involved in, and use allocators most people will be fine.