Support precompiled deserialize_in_place

precompiled/serde_derive/build.rs

@@ -1,3 +1,4 @@
 fn main() {
     println!("cargo:rustc-cfg=precompiled");
+    println!("cargo:rustc-cfg=feature=\"deserialize_in_place\"");
 }

precompiled/serde_derive/main.rs

@@ -3,6 +3,7 @@ extern crate proc_macro2;
 use proc_macro2::watt;
 use proc_macro2::watt::buffer::InputBuffer;
 use std::io::{self, Read, Write};
+use std::sync::atomic::Ordering;
 
 fn main() {
     let mut buf = Vec::new();
@@ -12,6 +13,10 @@ fn main() {
     let derive = match buf.read_u8() {
         0 => serde_derive::derive_serialize,
         1 => serde_derive::derive_deserialize,
+        2 => {
+            serde_derive::DESERIALIZE_IN_PLACE.store(true, Ordering::Relaxed);
+            serde_derive::derive_deserialize
+        }
         _ => unreachable!(),
     };
 

precompiled/x86_64-unknown-linux-gnu/Cargo.toml

@@ -16,6 +16,10 @@ repository = "https://github.com/serde-rs/serde"
 name = "serde_derive"
 proc-macro = true
 
+[features]
+default = []
+deserialize_in_place = []
+
 [package.metadata.docs.rs]
 targets = ["x86_64-unknown-linux-gnu"]
 

precompiled/x86_64-unknown-linux-gnu/src/lib.rs

@@ -23,7 +23,7 @@ pub fn derive_serialize(input: TokenStream) -> TokenStream {
 
 #[proc_macro_derive(Deserialize, attributes(serde))]
 pub fn derive_deserialize(input: TokenStream) -> TokenStream {
-    derive(1, input)
+    derive(1 + cfg!(feature = "deserialize_in_place") as u8, input)
 }
 
 fn derive(select: u8, input: TokenStream) -> TokenStream {

serde_derive/src/de.rs

@@ -1,5 +1,7 @@
 use proc_macro2::{Literal, Span, TokenStream};
 use quote::ToTokens;
+#[cfg(precompiled)]
+use std::sync::atomic::Ordering;
 use syn::punctuated::Punctuated;
 use syn::spanned::Spanned;
 use syn::{self, Ident, Index, Member};
@@ -304,6 +306,11 @@ fn deserialize_body(cont: &Container, params: &Parameters) -> Fragment {
 
 #[cfg(feature = "deserialize_in_place")]
 fn deserialize_in_place_body(cont: &Container, params: &Parameters) -> Option<Stmts> {
+    #[cfg(precompiled)]
+    if !crate::DESERIALIZE_IN_PLACE.load(Ordering::Relaxed) {
+        return None;
+    }
+
     // Only remote derives have getters, and we do not generate
     // deserialize_in_place for remote derives.
     assert!(!params.has_getter);

serde_derive/src/lib.rs

@@ -78,6 +78,8 @@ extern crate proc_macro2 as proc_macro;
 mod internals;
 
 use proc_macro::TokenStream;
+#[cfg(precompiled)]
+use std::sync::atomic::AtomicBool;
 use syn::DeriveInput;
 
 #[macro_use]
@@ -102,6 +104,9 @@ macro_rules! parse_macro_input {
     };
 }
 
+#[cfg(precompiled)]
+pub static DESERIALIZE_IN_PLACE: AtomicBool = AtomicBool::new(false);
+
 #[cfg_attr(not(precompiled), proc_macro_derive(Serialize, attributes(serde)))]
 pub fn derive_serialize(input: TokenStream) -> TokenStream {
     let mut input = parse_macro_input!(input as DeriveInput);