bitcoin-util: print genesis hash in display order #36471

bitcoin-util getchainparams prints the genesis hash byte-reversed compared to getblockhash 0:

bitcoin-util getchainparams | grep genesis

"genesis": "6fe28c0ab6f1b372c1a6a246ae63f74f931e8365e15a089c68d6190000000000",

bitcoin-cli getblockhash 0

000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f

Use GetHex() instead of HexStr(), consistent with pow.limit in the same output and with the RPCs.

The command is new in v32.0 (#35736), so I believe this should be backported before final release to avoid changing the output format afterwards.

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External sites

• Code coverage & benchmarks: https://corecheck.dev/bitcoin/bitcoin/pulls/36471
• Ralph review <img src=https://review.fish.foo/assets/bitcoin/bitcoin/36471.png alt="Ralph review status"> https://git.fish.foo/bitcoin/bitcoin/pulls/36471#author-ralph

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ACK cc8285e8c98ac91a380eec899bab2aed5863a458

code review ACK cc8285e8c98ac91a380eec899bab2aed5863a458

In theory, one could use something like this to make it more explicit:

diff --git a/src/uint256.h b/src/uint256.h
index d722916..62bb228 100644
--- a/src/uint256.h
+++ b/src/uint256.h
@@ -123,2 +123,6 @@ public:
 
+// See GetHex(). If HexStr is intended, use HexStr(std::span{self}).
+template <unsigned int BITS>
+std::string HexStr(const base_blob<BITS>&) = delete;
+
 template <unsigned int BITS>

But it will be a bit verbose and I am not sure if it really helps.

lgtm ACK cc8285e8c98ac91a380eec899bab2aed5863a458

Backported to 32.x in #36427.