Question: can the `BlockGasMeter` be used for absolute tx position?

The amount of consumed block gas is used [here](https://github.com/CosmWasm/wasmd/blob/1ff818801d4aa5dd6f483571ac7a38660c59c671/x/wasm/types/types.go#L212) to uniquely identify the position of a transaction in a block.

Is it possible that a transaction could consume zero gas, leading to a collision (that tx and the tx that follows will have the same "absolute index")?

Start by reading x/wasm/types/types.go at line 212 and inspect how BlockGasMeter-derived values identify transactions. Check whether zero-gas transactions can produce the same absolute index as the following transaction. Done when the issue has a documented answer about collision safety or a confirmed alternative.

Written by the indexing model from the issue text.