Use P2SH consensus rules for all blocks

This commit moves P2SH activation back to the genesis block, with
a hardcoded exception for the one historical block in the chain that
violated this rule.

1 files changed, 9 insertions, 2 deletions

diff --git a/src/validation.cpp b/src/validation.cpp
index cbbc857fdc..ac585895e5 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1730,8 +1730,15 @@ static unsigned int GetBlockScriptFlags(const CBlockIndex* pindex, const Consens
 
     unsigned int flags = SCRIPT_VERIFY_NONE;
 
-    // Start enforcing P2SH (BIP16)
-    if (pindex->nHeight >= consensusparams.BIP16Height) {
+    // BIP16 didn't become active until Apr 1 2012 (on mainnet, and
+    // retroactively applied to testnet)
+    // However, only one historical block violated the P2SH rules (on both
+    // mainnet and testnet), so for simplicity, always leave P2SH
+    // on except for the one violating block.
+    if (consensusparams.BIP16Exception.IsNull() || // no bip16 exception on this chain
+        pindex->phashBlock == nullptr || // this is a new candidate block, eg from TestBlockValidity()
+        *pindex->phashBlock != consensusparams.BIP16Exception) // this block isn't the historical exception
+    {
         flags |= SCRIPT_VERIFY_P2SH;
     }