Add dummy roc_alloc in roc_docs_cli for Windows

Cargo.lock

@@ -3592,6 +3592,7 @@ name = "roc_docs_cli"
 version = "0.0.1"
 dependencies = [
  "clap 3.2.11",
+ "libc",
  "roc_docs",
 ]
 

crates/docs_cli/Cargo.toml

@@ -19,3 +19,6 @@ bench = false
 [dependencies]
 roc_docs = { path = "../docs" }
 clap = { version = "3.1.15", default-features = false, features = ["std", "color", "suggestions", "derive"] }
+
+[target.'cfg(windows)'.dependencies]
+libc = "0.2.106"

crates/docs_cli/src/main.rs

@@ -48,3 +48,40 @@ fn roc_files_recursive<P: AsRef<Path>>(
 
     Ok(())
 }
+
+// These functions don't end up in the final Roc binary but Windows linker needs a definition inside the crate.
+// On Windows, there seems to be less dead-code-elimination than on Linux or MacOS, or maybe it's done later.
+#[cfg(windows)]
+#[allow(unused_imports)]
+use windows_roc_platform_functions::*;
+
+#[cfg(windows)]
+mod windows_roc_platform_functions {
+    use core::ffi::c_void;
+
+    /// # Safety
+    /// The Roc application needs this.
+    #[no_mangle]
+    pub unsafe fn roc_alloc(size: usize, _alignment: u32) -> *mut c_void {
+        libc::malloc(size)
+    }
+
+    /// # Safety
+    /// The Roc application needs this.
+    #[no_mangle]
+    pub unsafe fn roc_realloc(
+        c_ptr: *mut c_void,
+        new_size: usize,
+        _old_size: usize,
+        _alignment: u32,
+    ) -> *mut c_void {
+        libc::realloc(c_ptr, new_size)
+    }
+
+    /// # Safety
+    /// The Roc application needs this.
+    #[no_mangle]
+    pub unsafe fn roc_dealloc(c_ptr: *mut c_void, _alignment: u32) {
+        libc::free(c_ptr)
+    }
+}