Program mutable lamports (#4964)

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

@@ -0,0 +1,21 @@
+//! @brief Example Rust-based BPF program that moves a lamport from one account to another
+
+#![no_std]
+#![allow(unreachable_code)]
+#![allow(unused_attributes)]
+
+extern crate solana_sdk_bpf_utils;
+
+use solana_sdk_bpf_utils::entrypoint::*;
+use solana_sdk_bpf_utils::{entrypoint, info};
+
+entrypoint!(process_instruction);
+fn process_instruction(ka: &mut [SolKeyedAccount], _info: &SolClusterInfo, _data: &[u8]) -> bool {
+    // account 0 is the mint and not owned by this program, any debit of its lamports
+    // should result in a failed program execution.  Test to ensure that this debit
+    // is seen by the runtime and fails as expected
+    *ka[0].lamports -= 1;
+
+    info!("Success");
+    true
+}