core/vm/runtime: set random to enable merge-opcodes

[holiman]

This PR closes #29782 and #29722 . The IsMerge indicator used by core/vm/runtime checked if the prevrandao/random was set. This is actually a somewhat sane indicator, because if it is nil, it will trigger a nil deref later on if the RANDOM opcode is used.

This PR fixes it by setting it in case we're past Shanghai.

[user@work go-ethereum]$ go run ./cmd/evm --nomemory=false --json --code 5f44 run 
{"pc":0,"op":95,"gas":"0x2540be400","gasCost":"0x2","memSize":0,"stack":[],"depth":1,"refund":0,"opName":"PUSH0"}
{"pc":1,"op":68,"gas":"0x2540be3fe","gasCost":"0x2","memSize":0,"stack":["0x0"],"depth":1,"refund":0,"opName":"DIFFICULTY"}
{"pc":2,"op":0,"gas":"0x2540be3fc","gasCost":"0x0","memSize":0,"stack":["0x0","0x0"],"depth":1,"refund":0,"opName":"STOP"}
{"output":"","gasUsed":"0x4"}

[s1na]

It seems like block number can be overriden. Is the *t == 0 check enough?

[holiman]

No, it's strictly enough nor correct. We're checking shanghai but shanghai is after merge. This change just makes it work better than it does right now.

[rjl493456442]

Shouldn't we also enable these forks by default?

e.g.

diff --git a/core/vm/runtime/runtime.go b/core/vm/runtime/runtime.go
index b587d6d5a0..9c448a80c7 100644
--- a/core/vm/runtime/runtime.go
+++ b/core/vm/runtime/runtime.go
@@ -57,21 +57,32 @@ type Config struct {
 // sets defaults on the config
 func setDefaults(cfg *Config) {
 	if cfg.ChainConfig == nil {
+		var (
+			shanghaiTime = uint64(0)
+			cancunTime   = uint64(0)
+		)
 		cfg.ChainConfig = &params.ChainConfig{
-			ChainID:             big.NewInt(1),
-			HomesteadBlock:      new(big.Int),
-			DAOForkBlock:        new(big.Int),
-			DAOForkSupport:      false,
-			EIP150Block:         new(big.Int),
-			EIP155Block:         new(big.Int),
-			EIP158Block:         new(big.Int),
-			ByzantiumBlock:      new(big.Int),
-			ConstantinopleBlock: new(big.Int),
-			PetersburgBlock:     new(big.Int),
-			IstanbulBlock:       new(big.Int),
-			MuirGlacierBlock:    new(big.Int),
-			BerlinBlock:         new(big.Int),
-			LondonBlock:         new(big.Int),
+			ChainID:                       big.NewInt(1),
+			HomesteadBlock:                new(big.Int),
+			DAOForkBlock:                  new(big.Int),
+			DAOForkSupport:                false,
+			EIP150Block:                   new(big.Int),
+			EIP155Block:                   new(big.Int),
+			EIP158Block:                   new(big.Int),
+			ByzantiumBlock:                new(big.Int),
+			ConstantinopleBlock:           new(big.Int),
+			PetersburgBlock:               new(big.Int),
+			IstanbulBlock:                 new(big.Int),
+			MuirGlacierBlock:              new(big.Int),
+			BerlinBlock:                   new(big.Int),
+			LondonBlock:                   new(big.Int),
+			ArrowGlacierBlock:             nil,
+			GrayGlacierBlock:              nil,
+			TerminalTotalDifficulty:       big.NewInt(0),
+			TerminalTotalDifficultyPassed: true,
+			MergeNetsplitBlock:            nil,
+			ShanghaiTime:                  &shanghaiTime,
+			CancunTime:                    &cancunTime,
 		}
 	}