instruction: Add no_std support (anza-xyz#627)

* Use alloc directly

* Add to check-no-std script

* Clean up features

Author: febo

Cargo.lock

@@ -337,7 +337,7 @@ tiny-bip39 = "2.0.0"
 toml = "0.8.23"
 uriparse = "0.6.4"
 wasm-bindgen = "0.2.100"
-wincode = { version = "0.4.7", features = ["derive"], default-features = false }
+wincode = { version = "0.4.8", features = ["derive"], default-features = false }
 
 [profile.release]
 split-debuginfo = "unpacked"

Cargo.toml

@@ -19,9 +19,10 @@ bincode = ["dep:bincode", "dep:serde"]
 borsh = ["dep:borsh"]
 default = ["std"]
 frozen-abi = ["dep:solana-frozen-abi", "dep:solana-frozen-abi-macro", "serde", "std"]
-serde = ["dep:serde", "dep:serde_derive", "solana-pubkey/serde"]
-std = ["serde?/std", "borsh?/std"]
-syscalls = ["std"]
+serde = ["serde/alloc", "dep:serde_derive", "solana-pubkey/serde"]
+# The `std` feature is currently unused and retained for backwards compatibility.
+std = []
+syscalls = []
 wincode = ["dep:wincode", "solana-pubkey/wincode"]
 
 [dependencies]

instruction/Cargo.toml

@@ -14,18 +14,15 @@
 #![allow(clippy::arithmetic_side_effects)]
 #![no_std]
 
-#[cfg(feature = "std")]
-extern crate std;
-use solana_pubkey::Pubkey;
-#[cfg(feature = "std")]
-use std::vec::Vec;
+extern crate alloc;
+
 pub mod account_meta;
-#[cfg(feature = "std")]
-pub use account_meta::AccountMeta;
-pub use solana_instruction_error as error;
 #[cfg(any(feature = "syscalls", target_os = "solana"))]
 pub mod syscalls;
 
+pub use {account_meta::AccountMeta, solana_instruction_error as error};
+use {alloc::vec::Vec, solana_pubkey::Pubkey};
+
 /// A directive for a single invocation of a Solana program.
 ///
 /// An instruction specifies which program it is calling, which accounts it may
@@ -85,7 +82,6 @@ pub mod syscalls;
 /// Programs may require signatures from some accounts, in which case they
 /// should be specified as signers during `Instruction` construction. The
 /// program must still validate during execution that the account is a signer.
-#[cfg(feature = "std")]
 #[cfg_attr(
     feature = "serde",
     derive(serde_derive::Serialize, serde_derive::Deserialize)
@@ -101,7 +97,6 @@ pub struct Instruction {
     pub data: Vec<u8>,
 }
 
-#[cfg(feature = "std")]
 impl Instruction {
     #[cfg(feature = "borsh")]
     /// Create a new instruction from a value, encoded with [`borsh`].
@@ -344,7 +339,6 @@ pub struct BorrowedAccountMeta<'a> {
 ///
 /// This struct is used by the runtime when constructing the instructions sysvar. It is not
 /// useful to Solana programs.
-#[cfg(feature = "std")]
 pub struct BorrowedInstruction<'a> {
     pub program_id: &'a Pubkey,
     pub accounts: Vec<BorrowedAccountMeta<'a>>,

instruction/src/lib.rs

@@ -59,8 +59,8 @@ pub fn get_processed_sibling_instruction(index: usize) -> Option<Instruction> {
                 &mut account_meta as *mut _ as *mut u8,
             )
         } {
-            let mut data = std::vec::Vec::new();
-            let mut accounts = std::vec::Vec::new();
+            let mut data = alloc::vec::Vec::new();
+            let mut accounts = alloc::vec::Vec::new();
             data.resize_with(meta.data_len as usize, u8::default);
             accounts.resize_with(meta.accounts_len as usize, AccountMeta::default);
 

instruction/src/syscalls.rs

@@ -43,6 +43,7 @@ no_std_crates=(
 # These are only checked in the alloc+core pass, not the core-only pass.
 no_std_alloc_crates=(
   -p solana-account-info
+  -p solana-instruction
 )
 
 # Use the upstream BPF target, which doesn't support std, to make sure that our