Support non-nightly no_std builds

mos6502/src/lib.rs

@@ -1,5 +1,4 @@
 #![cfg_attr(not(feature = "std"), no_std)]
-#![cfg_attr(not(feature = "std"), feature(error_in_core))]
 
 #![allow(non_snake_case)]
 #![allow(non_upper_case_globals)]
@@ -16,4 +15,4 @@ extern crate bitflags;
 mod virtual_mos6502_decoder;
 mod virtual_mos6502;
 
-pub use virtual_mos6502::{Interface, State, Context, Address, EmulationStatus, decode_instruction};
+pub use virtual_mos6502::{Interface, State, Context, Address, EmulationError, EmulationStatus, decode_instruction};

mos6502/src/virtual_mos6502.rs

@@ -224,7 +224,8 @@ impl fmt::Display for EmulationError {
     }
 }
 
-impl core::error::Error for EmulationError {
+#[cfg(feature = "std")]
+impl std::error::Error for EmulationError {
     fn description( &self ) -> &str {
         use self::EmulationError::*;
         match *self {

nes/src/lib.rs

@@ -1,5 +1,4 @@
 #![cfg_attr(not(feature = "std"), no_std)]
-#![cfg_attr(not(feature = "std"), feature(error_in_core))]
 
 #![allow(dead_code)]
 #![allow(non_camel_case_types)]
@@ -54,6 +53,6 @@ mod filter;
 #[cfg(test)]
 mod testsuite;
 
-pub use virtual_nes::{Interface, State, Context, Button, ControllerPort};
+pub use virtual_nes::{Interface, State, Context, Button, ControllerPort, Error};
 pub use rp2c02::{Framebuffer, Palette};
 pub use rom::LoadError;

nes/src/rom.rs

@@ -1,6 +1,5 @@
 use core::cmp::max;
 use core::fmt;
-use core::error;
 use alloc::string::String;
 use alloc::vec::Vec;
 use alloc::format;
@@ -36,13 +35,8 @@ impl fmt::Display for LoadError {
     }
 }
 
-impl error::Error for LoadError {
+#[cfg(feature = "std")]
-    fn description( &self ) -> &str {
+impl std::error::Error for LoadError {}
-        match *self {
-            LoadError::Custom( ref message ) => &message[..],
-        }
-    }
-}
 
 pub const ROM_BANK_SIZE: usize = 16 * 1024;
 pub const VROM_BANK_SIZE: usize = 8 * 1024;

nes/src/virtual_nes.rs

@@ -1,4 +1,3 @@
-use core::error::Error;
 use core::mem;
 use alloc::boxed::Box;
 
@@ -11,6 +10,31 @@ use rom::{NesRom, LoadError};
 use emumisc::{WrappingExtra, PeekPoke, copy_memory};
 use memory_map::{translate_address_ram, translate_address_ioreg_ppu, translate_address_ioreg_other};
 
+#[derive(Debug)]
+pub struct Error( ErrorKind );
+
+impl core::fmt::Display for Error {
+    fn fmt( &self, fmt: &mut core::fmt::Formatter ) -> core::fmt::Result {
+        match self.0 {
+            ErrorKind::EmulationError( error ) => error.fmt( fmt )
+        }
+    }
+}
+
+#[derive(Debug)]
+enum ErrorKind {
+    EmulationError( mos6502::EmulationError )
+}
+
+impl From< mos6502::EmulationError > for Error {
+    fn from( error: mos6502::EmulationError ) -> Self {
+        Error( ErrorKind::EmulationError( error ) )
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for Error {}
+
 pub trait Context: Sized {
     fn state_mut( &mut self ) -> &mut State;
     fn state( &self ) -> &State;
@@ -38,15 +62,15 @@ pub trait Interface: Sized + Context {
         Private::copy_into_memory( self, offset, data )
     }
 
-    fn execute_until_vblank( &mut self ) -> Result< (), Box< dyn Error > > {
+    fn execute_until_vblank( &mut self ) -> Result< (), Error > {
         Private::execute_until_vblank( self )
     }
 
-    fn execute_for_a_frame( &mut self ) -> Result< (), Box< dyn Error > > {
+    fn execute_for_a_frame( &mut self ) -> Result< (), Error > {
         Private::execute_for_a_frame( self )
     }
 
-    fn execute_cycle( &mut self ) -> Result< bool, Box< dyn Error > > {
+    fn execute_cycle( &mut self ) -> Result< bool, Error > {
         Private::execute_cycle( self )
     }
 
@@ -94,7 +118,7 @@ pub struct State {
     apu_state: virtual_apu::State,
     dma_state: dma::State,
     mapper: Option< Box< dyn Mapper > >,
-    error: Option< Box< dyn Error > >,
+    error: Option< Error >,
     ready: bool,
     cpu_cycle: u32,
     frame_counter: u32,
@@ -366,7 +390,7 @@ trait Private: Sized + Context {
         copy_memory( data, &mut self.state_mut().ram[ offset as usize.. ] );
     }
 
-    fn execute_until_vblank( &mut self ) -> Result< (), Box< dyn Error > > {
+    fn execute_until_vblank( &mut self ) -> Result< (), Error > {
         if !self.state().ready {
             return Ok(());
         }
@@ -375,7 +399,7 @@ trait Private: Sized + Context {
         while self.state().frame_counter == last_counter_value {
             let result = mos6502::Interface::execute( self.newtype_mut() );
             if let Err( error ) = result {
-                self.state_mut().error = Some( Box::new( error ) );
+                self.state_mut().error = Some( error.into() );
                 break;
             }
         }
@@ -388,7 +412,7 @@ trait Private: Sized + Context {
         }
     }
 
-    fn execute_for_a_frame( &mut self ) -> Result< (), Box< dyn Error > > {
+    fn execute_for_a_frame( &mut self ) -> Result< (), Error > {
         if !self.state().ready {
             return Ok(());
         }
@@ -397,7 +421,7 @@ trait Private: Sized + Context {
         while self.state().full_frame_counter == last_counter_value {
             let result = mos6502::Interface::execute( self.newtype_mut() );
             if let Err( error ) = result {
-                self.state_mut().error = Some( Box::new( error ) );
+                self.state_mut().error = Some( error.into() );
                 break;
             }
         }
@@ -410,7 +434,7 @@ trait Private: Sized + Context {
         }
     }
 
-    fn execute_cycle( &mut self ) -> Result< bool, Box< dyn Error > > {
+    fn execute_cycle( &mut self ) -> Result< bool, Error > {
         let last_counter_value = self.state().full_frame_counter;
         mos6502::Interface::execute( self.newtype_mut() )?;