EVMC: Using `{.show.}` trace all calls from the host into the EVM

Show calls from the host into the EVM.  Shows the call, `evmc_message` fields,
and `evmc_result` fields when the call returns.

(When `show_tx_calls` is manually set to true.)

Signed-off-by: Jamie Lokier <jamie@shareable.org>

nimbus/transaction/evmc_host_glue.nim

@@ -90,7 +90,8 @@ proc evmc_create_nimbus_evm(): ptr evmc_vm {.cdecl, importc.}
 # a separate library yet.
 import ./evmc_vm_glue
 
-proc evmcExecComputation*(host: TransactionHost): EvmcResult =
+# This must be named `call` to show as "call" when traced by the `show` macro.
+proc call(host: TransactionHost): EvmcResult {.show, inline.} =
   let vm = evmc_create_nimbus_evm()
   if vm.isNil:
     echo "Warning: No EVM"
@@ -121,3 +122,6 @@ proc evmcExecComputation*(host: TransactionHost): EvmcResult =
                evmc_revision(host.vmState.fork), host.msg,
                if host.code.len > 0: host.code[0].unsafeAddr else: nil,
                host.code.len.csize_t)
+
+proc evmcExecComputation*(host: TransactionHost): EvmcResult =
+  call(host)

nimbus/transaction/host_trace.nim

@@ -18,6 +18,7 @@ func `$`(address: HostAddress): string = toHex(address)
 func `$`(txc: EvmcTxContext): string = &"gas_price={txc.tx_gas_price.fromEvmc}"
 func `$`(n: typeof(EvmcMessage().sender)): string = $n.fromEvmc
 func `$`(n: typeof(EvmcMessage().value)): string = $n.fromEvmc
+func `$`(host: TransactionHost): string = &"(fork={host.vmState.fork} message=${host.msg})"
 
 macro show*(fn: untyped): auto =
   if not show_tx_calls: