From f4f07fff17a3a13d78588409ef751c7b3f0ae448 Mon Sep 17 00:00:00 2001
From: Alex Beregszaszi <alex@rtfs.hu>
Date: Thu, 4 Jul 2019 21:00:44 +0100
Subject: [PATCH] rust: make ExecutionContext optional in EvmcVm.execute()

---
 bindings/rust/evmc-declare-tests/src/lib.rs |  2 +-
 bindings/rust/evmc-declare/src/lib.rs       | 18 ++++++++++--------
 bindings/rust/evmc-vm/src/container.rs      |  6 +++---
 bindings/rust/evmc-vm/src/lib.rs            |  2 +-
 examples/example-rust-vm/src/lib.rs         |  7 ++++++-
 5 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/bindings/rust/evmc-declare-tests/src/lib.rs b/bindings/rust/evmc-declare-tests/src/lib.rs
index a2ef12e98..8640d4fcf 100644
--- a/bindings/rust/evmc-declare-tests/src/lib.rs
+++ b/bindings/rust/evmc-declare-tests/src/lib.rs
@@ -22,7 +22,7 @@ impl EvmcVm for FooVM {
         _revision: evmc_sys::evmc_revision,
         _code: &[u8],
         _message: &ExecutionMessage,
-        _context: &mut ExecutionContext,
+        _context: Option<&mut ExecutionContext>,
     ) -> ExecutionResult {
         ExecutionResult::success(1337, None)
     }
diff --git a/bindings/rust/evmc-declare/src/lib.rs b/bindings/rust/evmc-declare/src/lib.rs
index 4821a5660..53e9dd580 100644
--- a/bindings/rust/evmc-declare/src/lib.rs
+++ b/bindings/rust/evmc-declare/src/lib.rs
@@ -22,14 +22,14 @@
 //!             ExampleVM {}
 //!     }
 //!
-//!     fn execute(&self, revision: evmc_vm::ffi::evmc_revision, code: &[u8], message: &evmc_vm::ExecutionMessage, context: &mut evmc_vm::ExecutionContext) -> evmc_vm::ExecutionResult {
+//!     fn execute(&self, revision: evmc_vm::ffi::evmc_revision, code: &[u8], message: &evmc_vm::ExecutionMessage, context: Option<&mut evmc_vm::ExecutionContext>) -> evmc_vm::ExecutionResult {
 //!             evmc_vm::ExecutionResult::success(1337, None)
 //!     }
 //! }
 //! ```
 
 // Set a higher recursion limit because parsing certain token trees might fail with the default of 64.
-#![recursion_limit = "128"]
+#![recursion_limit = "160"]
 
 extern crate proc_macro;
 
@@ -338,8 +338,6 @@ fn build_execute_fn(names: &VMNameSet) -> proc_macro2::TokenStream {
             use evmc_vm::EvmcVm;
 
             assert!(!instance.is_null());
-            // TODO: context is optional in case of the "precompiles" capability
-            assert!(!context.is_null());
             assert!(!msg.is_null());
 
             let execution_message: ::evmc_vm::ExecutionMessage = unsafe {
@@ -361,10 +359,14 @@ fn build_execute_fn(names: &VMNameSet) -> proc_macro2::TokenStream {
             };
 
             let result = ::std::panic::catch_unwind(|| {
-                let mut execution_context = unsafe {
-                  ::evmc_vm::ExecutionContext::new(context.as_mut().expect("EVMC context is null"))
-                };
-                container.execute(revision, code_ref, &execution_message, &mut execution_context)
+                if context.is_null() {
+                    container.execute(revision, code_ref, &execution_message, None)
+                } else {
+                    let mut execution_context = unsafe {
+                        ::evmc_vm::ExecutionContext::new(context.as_mut().expect("EVMC context is null"))
+                    };
+                    container.execute(revision, code_ref, &execution_message, Some(&mut execution_context))
+                }
             });
 
             let result = if result.is_err() {
diff --git a/bindings/rust/evmc-vm/src/container.rs b/bindings/rust/evmc-vm/src/container.rs
index 0bc512952..87705eba8 100644
--- a/bindings/rust/evmc-vm/src/container.rs
+++ b/bindings/rust/evmc-vm/src/container.rs
@@ -68,7 +68,7 @@ mod tests {
             _revision: evmc_sys::evmc_revision,
             _code: &[u8],
             _message: &ExecutionMessage,
-            _context: &mut ExecutionContext,
+            _context: Option<&mut ExecutionContext>,
         ) -> ExecutionResult {
             ExecutionResult::failure()
         }
@@ -141,7 +141,7 @@ mod tests {
                     evmc_sys::evmc_revision::EVMC_PETERSBURG,
                     &code,
                     &message,
-                    &mut context
+                    Some(&mut context)
                 )
                 .get_status_code(),
             ::evmc_sys::evmc_status_code::EVMC_FAILURE
@@ -157,7 +157,7 @@ mod tests {
                     evmc_sys::evmc_revision::EVMC_PETERSBURG,
                     &code,
                     &message,
-                    &mut context
+                    Some(&mut context)
                 )
                 .get_status_code(),
             ::evmc_sys::evmc_status_code::EVMC_FAILURE
diff --git a/bindings/rust/evmc-vm/src/lib.rs b/bindings/rust/evmc-vm/src/lib.rs
index d3071ddcd..4e1222d14 100644
--- a/bindings/rust/evmc-vm/src/lib.rs
+++ b/bindings/rust/evmc-vm/src/lib.rs
@@ -23,7 +23,7 @@ pub trait EvmcVm {
         revision: ffi::evmc_revision,
         code: &'a [u8],
         message: &'a ExecutionMessage,
-        context: &'a mut ExecutionContext<'a>,
+        context: Option<&'a mut ExecutionContext<'a>>,
     ) -> ExecutionResult;
 }
 
diff --git a/examples/example-rust-vm/src/lib.rs b/examples/example-rust-vm/src/lib.rs
index 360460a1f..009240b5d 100644
--- a/examples/example-rust-vm/src/lib.rs
+++ b/examples/example-rust-vm/src/lib.rs
@@ -19,8 +19,13 @@ impl EvmcVm for ExampleRustVM {
         _revision: evmc_sys::evmc_revision,
         _code: &'a [u8],
         message: &'a ExecutionMessage,
-        _context: &'a mut ExecutionContext<'a>,
+        _context: Option<&'a mut ExecutionContext<'a>>,
     ) -> ExecutionResult {
+        if _context.is_none() {
+            return ExecutionResult::failure();
+        }
+        let _context = _context.unwrap();
+
         if message.kind() != evmc_sys::evmc_call_kind::EVMC_CALL {
             return ExecutionResult::failure();
         }