Reason for stack violation warnings inside anchor macro generation

[sunguru98]

The anchor token extensions macro inside the Accounts struct was triggering the token extensions stack violations warnings after fiddling with the expanded code using cargo expand

The following code creates the "too many large-sized variables" warning

for e in extensions {
      match e {
            ::anchor_spl::token_interface::spl_token_2022::extension::ExtensionType::GroupPointer => {
                let cpi_program = token_program.to_account_info();
                let accounts = ::anchor_spl::token_interface::GroupPointerInitialize {
                    token_program_id: token_program.to_account_info(),
                    mint: mint.to_account_info(),
                };
                let cpi_ctx = anchor_lang::context::CpiContext::new(
                    cpi_program,
                    accounts,
                );
                ::anchor_spl::token_interface::group_pointer_initialize(
                    cpi_ctx,
                    Option::<anchor_lang::prelude::Pubkey>::None,
                    Option::<anchor_lang::prelude::Pubkey>::None,
                )?;
            }
            ::anchor_spl::token_interface::spl_token_2022::extension::ExtensionType::GroupMemberPointer => {
                let cpi_program = token_program.to_account_info();
                let accounts = ::anchor_spl::token_interface::GroupMemberPointerInitialize {
                    token_program_id: token_program.to_account_info(),
                    mint: mint.to_account_info(),
                };
                let cpi_ctx = anchor_lang::context::CpiContext::new(
                    cpi_program,
                    accounts,
                );
                ::anchor_spl::token_interface::group_member_pointer_initialize(
                    cpi_ctx,
                    Option::<anchor_lang::prelude::Pubkey>::Some(manager.key()),
                    Option::<anchor_lang::prelude::Pubkey>::None,
                )?;
            }
            ::anchor_spl::token_interface::spl_token_2022::extension::ExtensionType::MetadataPointer => {
                let cpi_program = token_program.to_account_info();
                let accounts = ::anchor_spl::token_interface::MetadataPointerInitialize {
                    token_program_id: token_program.to_account_info(),
                    mint: mint.to_account_info(),
                };
                let cpi_ctx = anchor_lang::context::CpiContext::new(
                    cpi_program,
                    accounts,
                );
                ::anchor_spl::token_interface::metadata_pointer_initialize(
                    cpi_ctx,
                    Option::<
                        anchor_lang::prelude::Pubkey,
                    >::Some(authority.key()),
                    Option::<anchor_lang::prelude::Pubkey>::Some(mint.key()),
                )?;
            }
            ::anchor_spl::token_interface::spl_token_2022::extension::ExtensionType::MintCloseAuthority => {
                let cpi_program = token_program.to_account_info();
                let accounts = ::anchor_spl::token_interface::MintCloseAuthorityInitialize {
                    token_program_id: token_program.to_account_info(),
                    mint: mint.to_account_info(),
                };
                let cpi_ctx = anchor_lang::context::CpiContext::new(
                    cpi_program,
                    accounts,
                );
                ::anchor_spl::token_interface::mint_close_authority_initialize(
                    cpi_ctx,
                    Option::<
                        &anchor_lang::prelude::Pubkey,
                    >::Some(&manager.key()),
                )?;
            }
            ::anchor_spl::token_interface::spl_token_2022::extension::ExtensionType::TransferHook => {
                let cpi_program = token_program.to_account_info();
                let accounts = ::anchor_spl::token_interface::TransferHookInitialize {
                    token_program_id: token_program.to_account_info(),
                    mint: mint.to_account_info(),
                };
                let cpi_ctx = anchor_lang::context::CpiContext::new(
                    cpi_program,
                    accounts,
                );
                ::anchor_spl::token_interface::transfer_hook_initialize(
                    cpi_ctx,
                    Option::<
                        anchor_lang::prelude::Pubkey,
                    >::Some(authority.key()),
                    Option::<anchor_lang::prelude::Pubkey>::None,
                )?;
            }
            ::anchor_spl::token_interface::spl_token_2022::extension::ExtensionType::NonTransferable => {
                let cpi_program = token_program.to_account_info();
                let accounts = ::anchor_spl::token_interface::NonTransferableMintInitialize {
                    token_program_id: token_program.to_account_info(),
                    mint: mint.to_account_info(),
                };
                let cpi_ctx = anchor_lang::context::CpiContext::new(
                    cpi_program,
                    accounts,
                );
                ::anchor_spl::token_interface::non_transferable_mint_initialize(
                    cpi_ctx,
                )?;
            }
            ::anchor_spl::token_interface::spl_token_2022::extension::ExtensionType::PermanentDelegate => {
                let cpi_program = token_program.to_account_info();
                let accounts = ::anchor_spl::token_interface::PermanentDelegateInitialize {
                    token_program_id: token_program.to_account_info(),
                    mint: mint.to_account_info(),
                };
                let cpi_ctx = anchor_lang::context::CpiContext::new(
                    cpi_program,
                    accounts,
                );
                ::anchor_spl::token_interface::permanent_delegate_initialize(
                    cpi_ctx,
                    Option::<
                        &anchor_lang::prelude::Pubkey,
                    >::Some(
                            &args
                                .permanent_delegate
                                .unwrap_or_else(|| manager.key())
                                .key(),
                        )
                        .unwrap(),
                )?;
            }
            _ => {}
     }
}

[sunguru98]

The match arms's variables were causing overload when too many extensions were iterated through. This is why, when fewer extensions were passed the warning wasn't occurring. The following minimalistic change immediately fixed that warning

for e in extensions {
      match e {
          ::anchor_spl::token_interface::spl_token_2022::extension::ExtensionType::GroupPointer => {
              ::anchor_spl::token_interface::group_pointer_initialize(
                  anchor_lang::context::CpiContext::new(
                  token_program.to_account_info(),
                  ::anchor_spl::token_interface::GroupPointerInitialize {
                  token_program_id: token_program.to_account_info(),
                  mint: mint.to_account_info(),
              },
              ),
                  Option::<anchor_lang::prelude::Pubkey>::None,
                  Option::<anchor_lang::prelude::Pubkey>::None,
              )?;
          }
          ::anchor_spl::token_interface::spl_token_2022::extension::ExtensionType::GroupMemberPointer => {
              ::anchor_spl::token_interface::group_member_pointer_initialize(
                  anchor_lang::context::CpiContext::new(
                  token_program.to_account_info(),
                  ::anchor_spl::token_interface::GroupMemberPointerInitialize {
                  token_program_id: token_program.to_account_info(),
                  mint: mint.to_account_info(),
              },
              ),
                  Option::<anchor_lang::prelude::Pubkey>::Some(manager.key()),
                  Option::<anchor_lang::prelude::Pubkey>::None,
              )?;
          }
          ::anchor_spl::token_interface::spl_token_2022::extension::ExtensionType::MetadataPointer => {
              ::anchor_spl::token_interface::metadata_pointer_initialize(
                  anchor_lang::context::CpiContext::new(
                  token_program.to_account_info(),
                  ::anchor_spl::token_interface::MetadataPointerInitialize {
                  token_program_id: token_program.to_account_info(),
                  mint: mint.to_account_info(),
              },
              ),
                  Option::<
                      anchor_lang::prelude::Pubkey,
                  >::Some(authority.key()),
                  Option::<anchor_lang::prelude::Pubkey>::Some(mint.key()),
              )?;
          }
          ::anchor_spl::token_interface::spl_token_2022::extension::ExtensionType::MintCloseAuthority => {
              ::anchor_spl::token_interface::mint_close_authority_initialize(
                  anchor_lang::context::CpiContext::new(
                  token_program.to_account_info(),
                  ::anchor_spl::token_interface::MintCloseAuthorityInitialize {
                  token_program_id: token_program.to_account_info(),
                  mint: mint.to_account_info(),
              },
              ),
                  Option::<
                      &anchor_lang::prelude::Pubkey,
                  >::Some(&manager.key()),
              )?;
          }
          ::anchor_spl::token_interface::spl_token_2022::extension::ExtensionType::TransferHook => {
              ::anchor_spl::token_interface::transfer_hook_initialize(
                  anchor_lang::context::CpiContext::new(
                  token_program.to_account_info(),
                  ::anchor_spl::token_interface::TransferHookInitialize {
                  token_program_id: token_program.to_account_info(),
                  mint: mint.to_account_info(),
              },
              ),
                  Option::<
                      anchor_lang::prelude::Pubkey,
                  >::Some(authority.key()),
                  Option::<anchor_lang::prelude::Pubkey>::None,
              )?;
          }
          ::anchor_spl::token_interface::spl_token_2022::extension::ExtensionType::NonTransferable => {
              ::anchor_spl::token_interface::non_transferable_mint_initialize(
                  anchor_lang::context::CpiContext::new(
                  token_program.to_account_info(),
                  ::anchor_spl::token_interface::NonTransferableMintInitialize {
                  token_program_id: token_program.to_account_info(),
                  mint: mint.to_account_info(),
              },
              ),
              )?;
          }
          ::anchor_spl::token_interface::spl_token_2022::extension::ExtensionType::PermanentDelegate => {
              ::anchor_spl::token_interface::permanent_delegate_initialize(
                  anchor_lang::context::CpiContext::new(
                  token_program.to_account_info(),
                  ::anchor_spl::token_interface::PermanentDelegateInitialize {
                  token_program_id: token_program.to_account_info(),
                  mint: mint.to_account_info(),
              },
              ),
                  Option::<
                      &anchor_lang::prelude::Pubkey,
                  >::Some(
                          &args
                              .permanent_delegate
                              .unwrap_or_else(|| manager.key())
                              .key(),
                      )
                      .unwrap(),
              )?;
          }
          _ => {}
      }
  }

We just need to find the macro generation part in anchor-spl to update towards the latest fix and that should probably remove the warning.

[kespinola]

resolved by

https://github.com/coral-xyz/anchor/pull/2913

We are still waiting for the next release of anchor to make use of it in WNS.