Anchor Space Allocation Remediation

Overview

Related Detector: Anchor Space Allocation

Incorrect space allocation causes initialization failures. The fix is to use Anchor’s InitSpace derive macro and always add the 8-byte discriminator prefix.

Recommended Fix

#[account]
#[derive(InitSpace)]
pub struct MyData {
    pub owner: Pubkey,        // 32
    pub amount: u64,          // 8
    #[max_len(100)]
    pub name: String,         // 4 + 100
}

#[derive(Accounts)]
pub struct Init<'info> {
    #[account(init, payer = user, space = 8 + MyData::INIT_SPACE)]
    pub data: Account<'info, MyData>,
}

Alternative Mitigations

Manual Calculation Reference

If not using InitSpace, calculate manually with this reference:

Type	Size
bool	1
u8/i8	1
u16/i16	2
u32/i32	4
u64/i64	8
u128/i128	16
Pubkey	32
Vec<T>	4 + (len * sizeof(T))
String	4 + len
Option<T>	1 + sizeof(T)

Always add 8 bytes for the Anchor discriminator.

Common Mistakes

Mistake: Forgetting the Discriminator

// WRONG: missing 8-byte discriminator
#[account(init, payer = user, space = 32 + 8)]  // Should be 8 + 32 + 8

Mistake: Forgetting Vec/String Length Prefix

// WRONG: String needs 4 bytes for Borsh length prefix
// space = 8 + 32 + 100  -- should be 8 + 32 + (4 + 100)

References

• Anchor — Space Reference
• CWE-131: Incorrect Calculation of Buffer Size