solitaire: shrink stack footprint by boxing FromAccounts::from()

solana/solitaire/program/src/lib.rs

@@ -83,7 +83,7 @@ impl CreationLamports {
 /// Trait definition that describes types that can be constructed from a list of solana account
 /// references. A list of dependent accounts is produced as a side effect of the parsing stage.
 pub trait FromAccounts<'a, 'b: 'a> {
-    fn from<T>(_: &'a Pubkey, _: &mut Iter<'a, AccountInfo<'b>>, _: &'a T) -> Result<Self>
+    fn from<T>(_: &'a Pubkey, _: &mut Iter<'a, AccountInfo<'b>>, _: &'a T) -> Result<Box<Self>>
     where
         Self: Sized;
 }

solana/solitaire/program/src/macros.rs

@@ -64,7 +64,7 @@ macro_rules! solitaire {
                         let ix_data = BorshDeserialize::try_from_slice(d).map_err(|e| SolitaireError::InstructionDeserializeFailed(e))?;
                         let mut accounts = FromAccounts::from(p, &mut a.iter(), &())?;
                         $fn(&ExecutionContext{program_id: p, accounts: a}, &mut accounts, ix_data)?;
-                        Persist::persist(&accounts, p)?;
+                        Persist::persist(accounts.as_ref(), p)?;
                         Ok(())
                     }
                 }

solana/solitaire/rocksalt/src/lib.rs

@@ -53,7 +53,7 @@ pub fn derive_from_accounts(input: TokenStream) -> TokenStream {
     let expanded = quote! {
         /// Macro generated implementation of FromAccounts by Solitaire.
         impl #combined_impl_g solitaire::FromAccounts #peel_type_g for #name #type_g {
-            fn from<DataType>(pid: &'a solana_program::pubkey::Pubkey, iter: &mut std::slice::Iter<'a, solana_program::account_info::AccountInfo<'b>>, data: &'a DataType) -> solitaire::Result<Self> {
+            fn from<DataType>(pid: &'a solana_program::pubkey::Pubkey, iter: &mut std::slice::Iter<'a, solana_program::account_info::AccountInfo<'b>>, data: &'a DataType) -> solitaire::Result<Box<Self>> {
                 #from_method
             }
         }
@@ -108,7 +108,9 @@ fn generate_fields(name: &syn::Ident, data: &Data) -> TokenStream2 {
                         use solitaire::trace;
                         trace!("Peeling:");
                         #(#recurse;)*
-                        Ok(#name { #(#names,)* })
+                        // Necessary evil; Helps respect the 4K max
+                        // stack frame size of the BPF VM
+                        Ok(Box::new(#name { #(#names,)* }))
                     }
                 }