AIs can fail at requesting 170 years inflation loan with a 4% interest rate

[SamuXarick]

The AI is setting loan amount to £1,641,693,900,000 and has a current loan of £82,050,000.

OpenTTD/src/script/api/script_company.cpp

Lines 207 to 209 in edbb5f4

	return ScriptObject::DoCommand(0,
	abs(loan - GetLoanAmount()), 2,
	(loan > GetLoanAmount()) ? CMD_INCREASE_LOAN : CMD_DECREASE_LOAN);

Following the code, abs(1,641,693,900,000 - 82,050,000) = 1,641,611,850,000 is passed to this function:

OpenTTD/src/script/api/script_object.hpp

Lines 69 to 72 in edbb5f4

	/**
	* Executes a raw DoCommand for the script.
	*/
	static bool DoCommand(TileIndex tile, uint32 p1, uint32 p2, uint cmd, const char *text = nullptr, Script_SuspendCallbackProc *callback = nullptr);

uint32 p1 transforms the value to 934,342,928
This ends up failing to set the loan even to the bugged value:

OpenTTD/src/misc_cmd.cpp

Lines 57 to 58 in edbb5f4

	case 2: // Take the given amount of loan
	if ((int32)p1 < LOAN_INTERVAL || c->current_loan + (int32)p1 > _economy.max_loan || p1 % LOAN_INTERVAL != 0) return CMD_ERROR;

p1 % LOAN_INTERVAL != 0 is true, returns CMD_ERROR

[glx22]

I think it should be possible to split 64bit value in two 32bit values passed in p1 and p2, with lower 2 bits discarded in the call, then forced to 0 in CmdIncreaseLoan() when reconstruction the original 64bit value. Amount being a multiple of LOAN_INTERVAL it should be fine.

[James103]

Possible workaround: In the AI script, set the loan value to incrementally higher amounts. For example, do the following:

AICompany.SetLoanAmount(2000000000);
AICompany.SetLoanAmount(4000000000);
AICompany.SetLoanAmount(6000000000);
AICompany.SetLoanAmount(8000000000);
...

until the target loan amount has been reached.