Runtime behavior

Hydrogen programs use managed class objects, immutable byte strings, and mutable arrays. Allocation and collection are automatic. Class and array assignment copy references.

Linux-native executables

The compiler embeds a Linux x86-64 runtime using raw Linux syscalls for console, files, and memory mappings. It does not depend on libc, a C++ runtime, an assembler, or a linker at application compilation time.

The heap uses a conservative, non-moving mark/sweep collector. Stack/register values and heap payloads are scanned for allocation and interior pointers. Reachable graphs and cycles are retained; unreachable mappings are reclaimed. Conservative scanning can retain values that are no longer logically reachable.

Null access, out-of-range indices, malformed integers, failed I/O, and allocation failure report errors and terminate with status 1.

UEFI output

The uefi-x64 target has no embedded managed runtime. It is a small PE32+ firmware application that directly calls the UEFI text-console service for the restricted Hello World profile.