Proposed BIP for OP_CAT

The email discusses the topic of stack size limits in Bitcoin Core and whether they are sufficient. The sender expresses their belief that the current limit of 520 bytes is not enough, especially without the presence of rolling sha2 opcodes. They suggest that if these opcodes were available, then a limit of 65 bytes might be acceptable. However, since they are not currently available, it is unclear what value would be considered "enough".

The sender mentions that for emulation purposes related to CHECKSIGFROMSTACK, it would be ideal to have the ability to construct a full transaction on the stack, which would require a 4M limit. However, they acknowledge that minimizing changes and sticking with the existing 520 bytes limit may be a more feasible strategy to achieve consensus.

They also bring up the point that Bitcoin Core currently limits the stack size to 1000 elements, each with 520 bytes, resulting in a theoretical limit of 520k. They clarify that Bitcoin Core does not explicitly count the "total stack size" as suggested by the recipient, but rather enforces the two existing limits separately.

The sender believes that adding a "total stack size limit" would introduce accounting complexity and impact other opcodes, making it unlikely to gain consensus. They conclude their email by providing their contact information and a lighthearted quote about the sun always shining in space.

Overall, the email discusses the limitations of stack size in Bitcoin Core and weighs the pros and cons of increasing the limit. It provides insights into the challenges and considerations involved in making changes to the existing system.