Add support for idiomatic error handling to BPF instruction processors (#7968)

programs/bpf/rust/error_handling/src/lib.rs

@@ -0,0 +1,60 @@
+//! @brief Example Rust-based BPF program that exercises error handling
+
+extern crate solana_sdk;
+use num_derive::FromPrimitive;
+use solana_sdk::{
+    account_info::AccountInfo, entrypoint, info, program_error::ProgramError, pubkey::Pubkey,
+};
+use thiserror::Error;
+
+/// Custom program errors
+#[derive(Error, Debug, Clone, PartialEq, FromPrimitive)]
+// Clippy compains about 0x8000_002d, but we don't care about C compatibility here
+#[allow(clippy::enum_clike_unportable_variant)]
+pub enum MyError {
+    #[error("The Answer")]
+    TheAnswer = 42,
+    #[error("Conflicting with success")]
+    ConflictingSuccess = 0,
+    #[error("Conflicting with builtin")]
+    ConflictingBuiltin = 0x8000_002d,
+}
+impl From<MyError> for ProgramError {
+    fn from(e: MyError) -> Self {
+        ProgramError::CustomError(e as u32)
+    }
+}
+
+entrypoint!(process_instruction);
+fn process_instruction(
+    _program_id: &Pubkey,
+    _accounts: &[AccountInfo],
+    instruction_data: &[u8],
+) -> Result<(), ProgramError> {
+    match instruction_data[0] {
+        1 => {
+            info!("return success");
+            Ok(())
+        }
+        2 => {
+            info!("return a builtin");
+            Err(ProgramError::AccountBorrowFailed)
+        }
+        3 => {
+            info!("return custom error");
+            Err(MyError::TheAnswer.into())
+        }
+        4 => {
+            info!("return error that conflicts with success");
+            Err(MyError::ConflictingSuccess.into())
+        }
+        5 => {
+            info!("return error that conflicts with builtin");
+            Err(MyError::ConflictingBuiltin.into())
+        }
+        _ => {
+            info!("Unrecognized command");
+            Err(ProgramError::InvalidInstructionData)
+        }
+    }
+}