added compiler flag sentinels to vm2 headers

why:
  making sure that deep links into vm2 sources are configured properly. it
  is intended that only the vm_*.nim interface headers are allowed to
  source files in vm2. the sentinels just protect from coding errors.

nimbus/vm2/computation.nim

@@ -5,6 +5,11 @@
 #  * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
 # at your option. This file may not be copied, modified, or distributed except according to those terms.
 
+when not defined(vm2_enabled):
+  {.fatal: "Flags \"vm2_enabled\" must be defined"}
+when defined(evmc_enabled):
+  {.fatal: "Flags \"evmc_enabled\" and \"vm2_enabled\" are mutually exclusive"}
+
 import
   chronicles, strformat, macros, options, times,
   sets, eth/[common, keys],

nimbus/vm2/interpreter.nim

@@ -8,6 +8,12 @@
 # at your option. This file may not be copied, modified, or distributed except
 # according to those terms.
 
+when not defined(vm2_enabled):
+  {.fatal: "Flags \"vm2_enabled\" must be defined"}
+when defined(evmc_enabled):
+  {.fatal: "Flags \"evmc_enabled\" and \"vm2_enabled\" are mutually exclusive"}
+
+
 # see vm_opcode_value
 import
   ./interpreter/opcode_values as vmo

nimbus/vm2/interpreter/gas_costs.nim

@@ -5,6 +5,11 @@
 #  * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
 # at your option. This file may not be copied, modified, or distributed except according to those terms.
 
+when not defined(vm2_enabled):
+  {.fatal: "Flags \"vm2_enabled\" must be defined"}
+when defined(evmc_enabled):
+  {.fatal: "Flags \"evmc_enabled\" and \"vm2_enabled\" are mutually exclusive"}
+
 import
   math, eth/common/eth_types,
   ./utils/[macros_gen_opcodes, utils_numeric],

nimbus/vm2/interpreter/opcode_values.nim

@@ -5,6 +5,11 @@
 #  * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
 # at your option. This file may not be copied, modified, or distributed except according to those terms.
 
+when not defined(vm2_enabled):
+  {.fatal: "Flags \"vm2_enabled\" must be defined"}
+when defined(evmc_enabled):
+  {.fatal: "Flags \"evmc_enabled\" and \"vm2_enabled\" are mutually exclusive"}
+
 import ./utils/macros_gen_opcodes
 
 fill_enum_holes:

nimbus/vm2/interpreter/utils/utils_numeric.nim

@@ -5,6 +5,11 @@
 #  * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
 # at your option. This file may not be copied, modified, or distributed except according to those terms.
 
+when not defined(vm2_enabled):
+  {.fatal: "Flags \"vm2_enabled\" must be defined"}
+when defined(evmc_enabled):
+  {.fatal: "Flags \"evmc_enabled\" and \"vm2_enabled\" are mutually exclusive"}
+
 import
   macros,
   stew/endians2, stew/ranges/ptr_arith,

nimbus/vm2/interpreter/vm_forks.nim

@@ -5,6 +5,11 @@
 #  * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
 # at your option. This file may not be copied, modified, or distributed except according to those terms.
 
+when not defined(vm2_enabled):
+  {.fatal: "Flags \"vm2_enabled\" must be defined"}
+when defined(evmc_enabled):
+  {.fatal: "Flags \"evmc_enabled\" and \"vm2_enabled\" are mutually exclusive"}
+
 import stint, eth/common/eth_types
 
 type

nimbus/vm2/memory.nim

@@ -5,6 +5,11 @@
 #  * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
 # at your option. This file may not be copied, modified, or distributed except according to those terms.
 
+when not defined(vm2_enabled):
+  {.fatal: "Flags \"vm2_enabled\" must be defined"}
+when defined(evmc_enabled):
+  {.fatal: "Flags \"evmc_enabled\" and \"vm2_enabled\" are mutually exclusive"}
+
 import
   sequtils,
   chronicles, eth/common/eth_types,

nimbus/vm2/message.nim

@@ -5,6 +5,11 @@
 #  * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
 # at your option. This file may not be copied, modified, or distributed except according to those terms.
 
+when not defined(vm2_enabled):
+  {.fatal: "Flags \"vm2_enabled\" must be defined"}
+when defined(evmc_enabled):
+  {.fatal: "Flags \"evmc_enabled\" and \"vm2_enabled\" are mutually exclusive"}
+
 import ./types
 
 proc isCreate*(message: Message): bool =

nimbus/vm2/precompiles.nim

@@ -1,3 +1,18 @@
+# Nimbus
+# Copyright (c) 2018 Status Research & Development GmbH
+# Licensed under either of
+#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
+#    http://www.apache.org/licenses/LICENSE-2.0)
+#  * MIT license ([LICENSE-MIT](LICENSE-MIT) or
+#    http://opensource.org/licenses/MIT)
+# at your option. This file may not be copied, modified, or distributed except
+# according to those terms.
+
+when not defined(vm2_enabled):
+  {.fatal: "Flags \"vm2_enabled\" must be defined"}
+when defined(evmc_enabled):
+  {.fatal: "Flags \"evmc_enabled\" and \"vm2_enabled\" are mutually exclusive"}
+
 import
   ./types,
   ./interpreter/[gas_meter, gas_costs, utils/utils_numeric, vm_forks],

nimbus/vm2/state.nim

@@ -8,6 +8,11 @@
 # at your option. This file may not be copied, modified, or distributed except
 # according to those terms.
 
+when not defined(vm2_enabled):
+  {.fatal: "Flags \"vm2_enabled\" must be defined"}
+when defined(evmc_enabled):
+  {.fatal: "Flags \"evmc_enabled\" and \"vm2_enabled\" are mutually exclusive"}
+
 import
   macros, strformat, tables, sets, options,
   eth/[common, keys, rlp], nimcrypto/keccak,

nimbus/vm2/state_transactions.nim

@@ -5,6 +5,11 @@
 #  * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
 # at your option. This file may not be copied, modified, or distributed except according to those terms.
 
+when not defined(vm2_enabled):
+  {.fatal: "Flags \"vm2_enabled\" must be defined"}
+when defined(evmc_enabled):
+  {.fatal: "Flags \"evmc_enabled\" and \"vm2_enabled\" are mutually exclusive"}
+
 import
   options, sets,
   eth/common, chronicles, ../db/accounts_cache,

nimbus/vm2/types.nim

@@ -8,6 +8,11 @@
 # at your option. This file may not be copied, modified, or distributed except
 # according to those terms.
 
+when not defined(vm2_enabled):
+  {.fatal: "Flags \"vm2_enabled\" must be defined"}
+when defined(evmc_enabled):
+  {.fatal: "Flags \"evmc_enabled\" and \"vm2_enabled\" are mutually exclusive"}
+
 import
   tables, eth/common,
   options, json, sets,