Ensure that library is no_std

Makefile

@@ -25,7 +25,7 @@ publish:
 	cargo publish -p musicxml
 
 checknostd:
-	cd ensure_no_std && cargo rustc -- -C link-arg=-nostartfiles
+	cd ensure_no_std && cargo build --release --target x86_64-unknown-none
 
 check:
 	cargo clippy -- -W clippy::all -W clippy::correctness -W clippy::suspicious -W clippy::complexity -W clippy::perf -W clippy::style -W clippy::pedantic -W clippy::panic -A clippy::doc_markdown -A clippy::wildcard_imports -A clippy::module_name_repetitions -D warnings

ensure_no_std/src/main.rs

@@ -1,9 +1,25 @@
 #![no_std]
 #![no_main]
-#[allow(unused_imports)]
 
+extern crate alloc;
+
+#[allow(unused_imports)]
 use musicxml;
 use core::panic::PanicInfo;
+use alloc::alloc::{GlobalAlloc, Layout};
+
+#[derive(Default)]
+pub struct Allocator;
+unsafe impl GlobalAlloc for Allocator {
+    unsafe fn alloc(&self, _layout: Layout) -> *mut u8 {
+        core::ptr::null_mut()
+    }
+    unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {
+    }
+}
+
+#[global_allocator]
+static GLOBAL_ALLOCATOR: Allocator = Allocator;
 
 #[panic_handler]
 fn panic(_info: &PanicInfo) -> ! {

musicxml/src/parser/zip_parser.rs

@@ -3,6 +3,9 @@
 use alloc::{collections::BTreeMap, vec::Vec};
 use miniz_oxide::inflate::decompress_to_vec;
 
+#[cfg(not(feature = "std"))]
+use alloc::string::{String, ToString};
+
 const DEFLATE_METHOD_CODE: u16 = 8;
 const LOCAL_FILE_HEADER_LEN: usize = core::mem::size_of::<LocalFileHeader>();
 const CENTRAL_FILE_HEADER_LEN: usize = core::mem::size_of::<CentralFileHeader>();