From 8e72b74515adf3eba6952d3d287b08ba16dacfdf Mon Sep 17 00:00:00 2001
From: febo <febo@anza.xyz>
Date: Tue, 18 Nov 2025 13:59:47 +0000
Subject: [PATCH 1/4] Add create account helper

---
 programs/system/src/lib.rs | 64 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)

diff --git a/programs/system/src/lib.rs b/programs/system/src/lib.rs
index 35268bc1..cff3f6c0 100644
--- a/programs/system/src/lib.rs
+++ b/programs/system/src/lib.rs
@@ -1,5 +1,69 @@
 #![no_std]
 
+use pinocchio::{
+    account_info::AccountInfo,
+    instruction::Signer,
+    pubkey::Pubkey,
+    sysvars::{rent::Rent, Sysvar},
+    ProgramResult,
+};
+
+use crate::instructions::{Assign, CreateAccount, Transfer};
+
 pub mod instructions;
 
 pinocchio_pubkey::declare_id!("11111111111111111111111111111111");
+
+/// Create an account with a minimal balance to be rent-exempt.
+///
+/// The account will be funded by the `payer` if its current lamports
+/// are insufficient for rent-exemption.
+#[inline(always)]
+pub fn create_account_with_minimal_balance(
+    account: &AccountInfo,
+    space: usize,
+    owner: &Pubkey,
+    payer: &AccountInfo,
+    signers: &[Signer],
+    rent_sysvar: Option<&AccountInfo>,
+) -> ProgramResult {
+    let lamports = if let Some(rent_sysvar) = rent_sysvar {
+        let rent = Rent::from_account_info(rent_sysvar)?;
+        rent.minimum_balance(space)
+    } else {
+        Rent::get()?.minimum_balance(space)
+    };
+
+    if account.lamports() == 0 {
+        CreateAccount {
+            from: payer,
+            to: account,
+            lamports,
+            space: space as u64,
+            owner,
+        }
+        .invoke_signed(signers)
+    } else {
+        let required_lamports = lamports.saturating_sub(account.lamports());
+
+        // Transfer lamports from `payer` to `account` if needed.
+        if required_lamports > 0 {
+            Transfer {
+                from: payer,
+                to: account,
+                lamports: required_lamports,
+            }
+            .invoke()?;
+        }
+
+        Assign { account, owner }.invoke_signed(signers)?;
+
+        // Allocates the required space for the account.
+        //
+        // SAFETY: There are no active borrows of the `account`.
+        // This was checked by the `Assign` CPI above.
+        unsafe { account.resize_unchecked(space)? };
+
+        Ok(())
+    }
+}

From e04e5990d748309925d95c3fc05e5b0a4b377512 Mon Sep 17 00:00:00 2001
From: febo <febo@anza.xyz>
Date: Tue, 18 Nov 2025 14:09:34 +0000
Subject: [PATCH 2/4] More comments

---
 programs/system/src/lib.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/programs/system/src/lib.rs b/programs/system/src/lib.rs
index cff3f6c0..117aaa3c 100644
--- a/programs/system/src/lib.rs
+++ b/programs/system/src/lib.rs
@@ -35,6 +35,7 @@ pub fn create_account_with_minimal_balance(
     };
 
     if account.lamports() == 0 {
+        // Create the account if it does not exist.
         CreateAccount {
             from: payer,
             to: account,
@@ -56,9 +57,10 @@ pub fn create_account_with_minimal_balance(
             .invoke()?;
         }
 
+        // Assign the account to the specified owner.
         Assign { account, owner }.invoke_signed(signers)?;
 
-        // Allocates the required space for the account.
+        // Allocate the required space for the account.
         //
         // SAFETY: There are no active borrows of the `account`.
         // This was checked by the `Assign` CPI above.

From 1466edae6f381eb436c1c6e2b350a6fa2f16a95e Mon Sep 17 00:00:00 2001
From: febo <febo@anza.xyz>
Date: Wed, 19 Nov 2025 11:15:27 +0000
Subject: [PATCH 3/4] Use signer seeds on transfer

---
 programs/system/src/lib.rs | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/programs/system/src/lib.rs b/programs/system/src/lib.rs
index 117aaa3c..8f4198d7 100644
--- a/programs/system/src/lib.rs
+++ b/programs/system/src/lib.rs
@@ -14,12 +14,17 @@ pub mod instructions;
 
 pinocchio_pubkey::declare_id!("11111111111111111111111111111111");
 
-/// Create an account with a minimal balance to be rent-exempt.
+/// Create an account with a minimum balance to be rent-exempt.
+///
+/// When creating a PDA `account`, the PDA signer seeds must be provided
+/// via the `signers`.
 ///
 /// The account will be funded by the `payer` if its current lamports
-/// are insufficient for rent-exemption.
+/// are insufficient for rent-exemption. The payer can be a PDA signer
+/// owned by the system program and its signer seeds can be provided
+/// via the `signers`.
 #[inline(always)]
-pub fn create_account_with_minimal_balance(
+pub fn create_account_with_minimum_balance(
     account: &AccountInfo,
     space: usize,
     owner: &Pubkey,
@@ -54,7 +59,7 @@ pub fn create_account_with_minimal_balance(
                 to: account,
                 lamports: required_lamports,
             }
-            .invoke()?;
+            .invoke_signed(signers)?;
         }
 
         // Assign the account to the specified owner.

From 31c337c0358db3f6876bf98ecc0f70a7598d4716 Mon Sep 17 00:00:00 2001
From: febo <febo@anza.xyz>
Date: Wed, 19 Nov 2025 11:45:35 +0000
Subject: [PATCH 4/4] Cosmetics

---
 programs/system/src/lib.rs | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/programs/system/src/lib.rs b/programs/system/src/lib.rs
index 8f4198d7..c326c6df 100644
--- a/programs/system/src/lib.rs
+++ b/programs/system/src/lib.rs
@@ -69,8 +69,6 @@ pub fn create_account_with_minimum_balance(
         //
         // SAFETY: There are no active borrows of the `account`.
         // This was checked by the `Assign` CPI above.
-        unsafe { account.resize_unchecked(space)? };
-
-        Ok(())
+        unsafe { account.resize_unchecked(space) }
     }
 }