state: Implement fake BLOCKHASH resolution for testing

If explict block hashes are not provided, return predefined block hashes from `Host::get_block_hash()` as `keccak256(str(block_number))`. This is badly documented convention used in state tests. Note: the readability of block hash values from `BLOCKHASH` instruction still applies. I.e. you will get 0 if you ask for a block from the future or more than 256 blocks older than the current one.
ethereum · Sep 4, 2023 · 51ccacb · 51ccacb
1 parent 778dfcb
commit 51ccacb
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Showing 4 changed files with 22 additions and 6 deletions.
diff --git a/test/state/host.cpp b/test/state/host.cpp
@@ -326,7 +326,10 @@ bytes32 Host::get_block_hash(int64_t block_number) const noexcept
         it != m_block.known_block_hashes.end())
         return it->second;
 
-    return {};
+    // Convention for testing: if the block hash in unknown return the predefined "fake" value.
+    // https://github.com/ethereum/go-ethereum/blob/v1.12.2/tests/state_test_util.go#L432
+    const auto s = std::to_string(block_number);
+    return keccak256({reinterpret_cast<const uint8_t*>(s.data()), s.size()});
 }
 
 void Host::emit_log(const address& addr, const uint8_t* data, size_t data_size,

diff --git a/test/unittests/evm_state_test.cpp b/test/unittests/evm_state_test.cpp
@@ -432,7 +432,7 @@ TEST_P(evm, blockhash)
     host.block_hash.bytes[13] = 0x13;
 
     host.tx_context.block_number = 0;
-    const auto code = push(0) + OP_BLOCKHASH + ret_top();
+    const auto code = blockhash(0) + ret_top();
     execute(code);
     EXPECT_EQ(result.status_code, EVMC_SUCCESS);
     EXPECT_EQ(gas_used, 38);

diff --git a/test/unittests/state_transition_block_test.cpp b/test/unittests/state_transition_block_test.cpp
@@ -24,17 +24,25 @@ TEST_F(state_transition, known_block_hash)
         {2, 0x0000000000000000000000000000000000000000000000000000000000000111_bytes32}};
     block.number = 5;
 
-    const auto code =
-        push(1) + OP_BLOCKHASH + push(0) + OP_SSTORE + push(2) + OP_BLOCKHASH + push(1) + OP_SSTORE;
-
     tx.to = To;
-    pre.insert(*tx.to, {.nonce = 1, .code = code});
+    pre.insert(*tx.to, {.nonce = 1, .code = sstore(0, blockhash(1)) + sstore(1, blockhash(2))});
     expect.post[To].storage[0x00_bytes32] =
         0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421_bytes32;
     expect.post[To].storage[0x01_bytes32] =
         0x0000000000000000000000000000000000000000000000000000000000000111_bytes32;
 }
 
+TEST_F(state_transition, known_block_hash_fake)
+{
+    block.number = 2;
+    tx.to = To;
+    pre.insert(*tx.to, {.nonce = 1, .code = sstore(0, blockhash(0)) + sstore(1, blockhash(1))});
+    expect.post[To].storage[0x00_bytes32] =
+        0x044852b2a670ade5407e78fb2863c51de9fcb96542a07186fe3aeda6bb8a116d_bytes32;
+    expect.post[To].storage[0x01_bytes32] =
+        0xc89efdaa54c0f20c7adf612882df0950f5a951637e0307cdcb4c672f298b8bc6_bytes32;
+}
+
 TEST_F(state_transition, block_apply_ommers_reward)
 {
     rev = EVMC_LONDON;

diff --git a/test/utils/bytecode.hpp b/test/utils/bytecode.hpp
@@ -348,6 +348,11 @@ inline bytecode tload(bytecode index)
     return index + OP_TLOAD;
 }
 
+inline bytecode blockhash(bytecode number)
+{
+    return number + OP_BLOCKHASH;
+}
+
 template <Opcode kind>
 struct call_instruction
 {