Add the extra-syscalls feature, which reduces code size.

Cargo.toml

@@ -60,5 +60,10 @@ be-std = []
 # Should c-scape's `memcpy` etc. use compiler-builtins?
 use-compiler-builtins = ["c-gull/use-compiler-builtins"]
 
+# This extends the `syscall` function with suppport for more syscalls. This is
+# not enabled by default because it increases the code size of `syscall` by
+# several kibibytes and isn't needed by most Rust programs.
+extra-syscalls = ["c-gull/extra-syscalls"]
+
 # Enable `todo!()` stubs for unimplemented functions.
 todo = ["c-gull/todo"]

example-crates/hello-world-small/README.md

@@ -13,10 +13,10 @@ $ RUSTFLAGS="-Zlocation-detail=none -C relocation-model=static -Ctarget-feature=
 This applies all the techniques described on the [min-sized-rust] page
 before [Remove `core::fmt` with `no_main` and Careful Usage of `libstd`].
 
-As of this writing, using all these same optimizations without Eyra, using
-`x86_64-unknown-linux-musl` (which produces smaller statically-linked binaries
-than `x86_64-unknown-linux-gnu`), compiles to 50776 bytes, while this Eyra
-example currently compiles to 37912 bytes.
+As of this writing, this compiles to 37880 bytes. For comparison, usinig all
+these same optimizations without Eyra, and using `x86_64-unknown-linux-musl`
+(which produces smaller statically-linked binaries than
+`x86_64-unknown-linux-gnu`), compiles to 50776 bytes.
 
 If you're interested in going further down the `#![no_main]`/`#![no_std]`
 path, consider [using Origin directly] which can get down to 408 bytes. Or,