multiple contracts deployed via deployContract cannot interact with each other about forge-std HOT 2 CLOSED

The issue here was a solidity issue with the users implementation, where the user was using address b = deployCode("AB.sol:B", abi.encodePacked(a)); instead of: address b = deployCode("AB.sol:B", abi.encode(a));. This resulted in the constructor arg for the address of A being wrong because abi.encodePacked doesnt left pad an address with 0 bytes like abi.encode does. So when B SSTOREs in the constructor, it SSTOREs like so:

// OP [Stack]
AND             [0xffffffffffffffffffffffffffffffffffffffff, <LEFT ALIGNED ADDRESS OF A (should be right aligned)>]
PUSH1(0x00)     [0x00000000042...ce0000000000000]
SSTORE          [0x000..000, 0x00000000042...ce0000000000000]

which results in the wrong address being stored in a, making codesize checks fail in B.

from forge-std.

Thanks @brockelmore. I can confirm that this was the issue and your solution worked, which was replacing
address b = deployCode("AB.sol:B", abi.encodePacked(a)); with address b = deployCode("AB.sol:B", abi.encode(a)); and generally brushing up on solidity abi encoding docs.

I would recommend adding some documentation or tests that show the argument encoding in action.

from forge-std.