Add rust duplicate account test program (#7897)

automerge

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

@@ -0,0 +1,48 @@
+//! @brief Example Rust-based BPF program that tests duplicate accounts passed via accounts
+
+extern crate solana_sdk;
+use solana_sdk::{
+    account_info::AccountInfo, entrypoint, entrypoint::SUCCESS, info, pubkey::Pubkey,
+};
+
+entrypoint!(process_instruction);
+fn process_instruction(_program_id: &Pubkey, accounts: &mut [AccountInfo], data: &[u8]) -> u32 {
+    const FAILURE: u32 = 1;
+
+    match data[0] {
+        1 => {
+            info!("modify first account data");
+            accounts[2].data[0] = 1;
+        }
+        2 => {
+            info!("modify first account data");
+            accounts[3].data[0] = 2;
+        }
+        3 => {
+            info!("modify both account data, should fail");
+            accounts[2].data[0] = 1;
+            accounts[3].data[0] = 2;
+        }
+        4 => {
+            info!("modify first account lamports");
+            *accounts[1].lamports -= 1;
+            *accounts[2].lamports += 1;
+        }
+        5 => {
+            info!("modify first account lamports");
+            *accounts[1].lamports -= 2;
+            *accounts[3].lamports += 2;
+        }
+        6 => {
+            info!("modify both account lamports, should fail");
+            *accounts[1].lamports -= 1;
+            *accounts[2].lamports += 1;
+            *accounts[3].lamports += 2;
+        }
+        _ => {
+            info!("Unrecognized command");
+            return FAILURE;
+        }
+    }
+    SUCCESS
+}