nimbus-eth1/nimbus/vm/types.nim

129 lines
3.7 KiB
Nim
Raw Normal View History

# 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.
import
tables, eth/common,
options, json, sets,
./memory, ./stack, ./code_stream,
./interpreter/[gas_costs, opcode_values, vm_forks],
# TODO - will be hidden at a lower layer
../db/[db_chain, accounts_cache]
when defined(evmc_enabled):
import
./evmc_api
EVMC: Small stacks when using EVMC, closes #575 (segfaults) This patch reduces stack space used with EVM in ENABLE_EVMC=1 mode, from 13 MB worst case to 550 kB, a 24x reduction. This completes fixing the "stack problem" and closes #575 (`EVM: Different segmentation faults when running the test suite with EVMC`). It also closes #256 (`recursive EVM call trigger unrecoverable stack overflow`). After this patch, it is possible to re-enable the CI targets which had to be disabled due to #575. This change is also a required precursor for switching over to "nearly EVMC" as the clean and focused Nimbus-internal API between EVM and sync/database processes, and is also key to the use of Chronos `async` in those processes when calling the EVM. (The motivation is the internal interface has to be substantially changed _anyway_ for the parallel sync and database processes, and EVMC turns out to be well-designed and well-suited for this. It provides good separation between modules, and suits our needs better than our other current interface. Might as well use a good one designed by someone else. EVMC is 98% done in Nimbus thanks to great work done before by @jangko, and we can use Nimbus-specific extensions where we need flexibility, including for performance. Being aligned with the ecosystem is a useful bonus feature.) All tests below were run on Ubuntu 20.04 LTS server, x86-64. This matches one of the targets that has been disabled for a while in CI in EVMC mode due to stack overflow crashing the tests, so it's a good choice. Measurements before =================== Testing commit `e76e0144 2021-04-22 11:29:42 +0700 add submodules: graphql and toml-serialization`. $ rm -f build/all_tests && make ENABLE_EVMC=1 test $ ulimit -S -s 16384 # Requires larger stack than default to avoid crash. $ ./build/all_tests 9 | tee tlog [Suite] persist block json tests ... Stack range 38416 depthHigh 3 ... Stack range 13074720 depthHigh 1024 [OK] tests/fixtures/PersistBlockTests/block1431916.json These tests use 13.07 MB of stack to run, and so crash with the default stack limit on Ubuntu Server 20.04 (8MB). Exactly 12768 bytes per EVM call stack frame. $ rm -f build/all_tests && make ENABLE_EVMC=1 test $ ulimit -S -s 16384 # Requires larger stack than default. $ ./build/all_tests 7 | tee tlog [Suite] new generalstate json tests ... Stack range 14384 depthHigh 2 ... Stack range 3495456 depthHigh 457 [OK] tests/fixtures/eth_tests/GeneralStateTests/stRandom2/randomStatetest639.json ... Stack range 3709600 depthHigh 485 [OK] tests/fixtures/eth_tests/GeneralStateTests/stRandom2/randomStatetest458.json ... Stack range 7831600 depthHigh 1024 [OK] tests/fixtures/eth_tests/GeneralStateTests/stCreate2/Create2OnDepth1024.json These tests use 7.83MB of stack to run. About 7648 bytes per EVM call stack frame. It _only just_ avoids crashing with the default Ubuntu Server stack limit of 8 MB. However, it still crashes on Windows x86-64, which is why the Windows CI EVMC target is currently disabled. On Linux where this passes, this is so borderline that it affects work and testing of the complex storage code, because that's called from the EVM. Also, this greatly exceeds the default thread stack size. Measurements after ================== $ rm -f build/all_tests && make ENABLE_EVMC=1 test $ ulimit -S -s 600 # Because we can! 600k stack. $ ./build/all_tests 9 | tee tlog [Suite] persist block json tests ... Stack range 1936 depthHigh 3 ... Stack range 556272 depthHigh 1022 Stack range 556512 depthHigh 1023 Stack range 556816 depthHigh 1023 Stack range 557056 depthHigh 1024 Stack range 557360 depthHigh 1024 [OK] tests/fixtures/PersistBlockTests/block1431916.json $ rm -f build/all_tests && make ENABLE_EVMC=1 test $ ulimit -S -s 600 # Because we can! 600k stack. $ ./build/all_tests 7 | tee tlog [Suite] new generalstate json tests ... Stack range 1392 depthHigh 2 ... Stack range 248912 depthHigh 457 [OK] tests/fixtures/eth_tests/GeneralStateTests/stRandom2/randomStatetest639.json ... Stack range 264144 depthHigh 485 [OK] tests/fixtures/eth_tests/GeneralStateTests/stRandom2/randomStatetest458.json ... Stack range 557360 depthHigh 1024 [OK] tests/fixtures/eth_tests/GeneralStateTests/stStaticCall/static_CallRecursiveBombPreCall.json For both tests, a satisfying *544 bytes* per EVM call stack frame, and EVM takes less than 600 kB total. With other overheads, both tests run in 600 kB stack total at maximum EVM depth. We must add some headroom on this for database activity called from the EVM, and different compile targets. But it means the EVM itself is no longer a stack burden. This is much smaller than the default thread stack size on Linux (2MB), with plenty of margin. (Just fyi, it isn't smaller than a _small_ thread stack on Linux from a long time ago (128kB), and some small embedded C targets.) This size is well suited to running EVMs in threads. Further reduction ================= This patch solves the stack problem. Windows and Linux 64-bit EVMC CI targets can be re-enabled, and there is no longer a problem with stack usage. We can reduce further to ~340 bytes per frame and 350 kB total, while still complying with EVMC. But as this involves changing how errors are handled to comply fully with EVMC, and removing `dispose` calls, it's not worth doing now while there are other EVMC changes in progress that will have the same effect. A Nimbus-specific extension will allow us to avoid recursion with EVMC anyway, bringing bytes per frame to zero. We need the extension anyway, to support Chronos `async` which parallel transaction processing is built around. Interop with non-Nimbus over EVMC won't let us avoid recursion, but then we can't control the stack frame size either. To prevent stack overflow in interop I anticipate using (this method in Aleth) [https://github.com/ethereum/aleth/blob/6e96ce34e3f131e2d42f3cb00741b54e05ab029d/libethereum/ExtVM.cpp#L61]. Smoke test other versions of GCC and Clang/LLVM =============================================== As all builds including Windows use GCC or Apple's Clang/LLVM, this is just to verify we're in the right ballpark on all targets. I've only checked `x86_64` though, not 32-bit, and not ARM. It's interesting to see GCC 10 uses less stack. This is because it optimises `struct` returns better, sometimes skipping an intermediate copy. Here it benefits the EVMC API, but I found GCC 10 also improves the larger stack usage of the rest of `nimbus-eth1` as well. Apple clang 12.0.0 (clang-1200.0.26.2) on MacOS 10.15: - 544 bytes per EVM call stack frame GCC 10.3.0 (Ubuntu 10.3.0-1ubuntu1) on Ubuntu 21.04: - 464 bytes per EVM call stack frame GCC 10.2.0 (Ubuntu 10.2.0-5ubuntu1~20.04) on Ubuntu 20.04 LTS: - 464 bytes per EVM call stack frame GCC 11.0.1 20210417 (experimental; Ubuntu 11-20210417-1ubuntu1) on Ubuntu 21.04: - 8 bytes per EVM call stack frame GCC 9.3.0 (Ubuntu 9.3.0-17ubuntu1~20.04) on Ubuntu 20.04 LTS: - 544 bytes per EVM call stack frame GCC 8.4.0 (Ubuntu 8.4.0-3ubuntu2) on Ubuntu 20.04 LTS: - 544 bytes per EVM call stack frame GCC 7.5.0 (Ubuntu 7.5.0-6ubuntu2) on Ubuntu 20.04 LTS: - 544 bytes per EVM call stack frame GCC 9.2.1 20191008 (Ubuntu 9.2.1-9ubuntu2) on Ubuntu 19.10: - 528 bytes per EVM call stack frame Signed-off-by: Jamie Lokier <jamie@shareable.org>
2021-04-26 15:01:00 +00:00
# Select between small-stack recursion and no recursion. Both are good, fast,
# low resource using methods. Keep both here because true EVMC API requires
# the small-stack method, but Chronos `async` is better without recursion.
const vm_use_recursion* = defined(evmc_enabled)
type
VMFlag* = enum
ExecutionOK
GenerateWitness
ClearCache
BaseVMState* = ref object of RootObj
prevHeaders* : seq[BlockHeader]
chaindb* : BaseChainDB
accessLogs* : AccessLogs
blockHeader* : BlockHeader
name* : string
flags* : set[VMFlag]
tracer* : TransactionTracer
logEntries* : seq[Log]
receipts* : seq[Receipt]
accountDb* : AccountsCache
cumulativeGasUsed*: GasInt
touchedAccounts*: HashSet[EthAddress]
suicides* : HashSet[EthAddress]
txOrigin* : EthAddress
txGasPrice* : GasInt
gasCosts* : GasCosts
fork* : Fork
minerAddress* : EthAddress
AccessLogs* = ref object
reads*: Table[string, string]
writes*: Table[string, string]
TracerFlags* {.pure.} = enum
EnableTracing
DisableStorage
DisableMemory
DisableStack
DisableState
DisableStateDiff
EnableAccount
TransactionTracer* = object
trace*: JsonNode
flags*: set[TracerFlags]
accounts*: HashSet[EthAddress]
storageKeys*: seq[HashSet[Uint256]]
Computation* = ref object
# The execution computation
vmState*: BaseVMState
when defined(evmc_enabled):
host*: HostContext
msg*: Message
memory*: Memory
stack*: Stack
returnStack*: seq[int]
gasMeter*: GasMeter
code*: CodeStream
output*: seq[byte]
returnData*: seq[byte]
error*: Error
touchedAccounts*: HashSet[EthAddress]
suicides*: HashSet[EthAddress]
logEntries*: seq[Log]
savePoint*: SavePoint
instr*: Op
opIndex*: int
EVMC: Small stacks when using EVMC, closes #575 (segfaults) This patch reduces stack space used with EVM in ENABLE_EVMC=1 mode, from 13 MB worst case to 550 kB, a 24x reduction. This completes fixing the "stack problem" and closes #575 (`EVM: Different segmentation faults when running the test suite with EVMC`). It also closes #256 (`recursive EVM call trigger unrecoverable stack overflow`). After this patch, it is possible to re-enable the CI targets which had to be disabled due to #575. This change is also a required precursor for switching over to "nearly EVMC" as the clean and focused Nimbus-internal API between EVM and sync/database processes, and is also key to the use of Chronos `async` in those processes when calling the EVM. (The motivation is the internal interface has to be substantially changed _anyway_ for the parallel sync and database processes, and EVMC turns out to be well-designed and well-suited for this. It provides good separation between modules, and suits our needs better than our other current interface. Might as well use a good one designed by someone else. EVMC is 98% done in Nimbus thanks to great work done before by @jangko, and we can use Nimbus-specific extensions where we need flexibility, including for performance. Being aligned with the ecosystem is a useful bonus feature.) All tests below were run on Ubuntu 20.04 LTS server, x86-64. This matches one of the targets that has been disabled for a while in CI in EVMC mode due to stack overflow crashing the tests, so it's a good choice. Measurements before =================== Testing commit `e76e0144 2021-04-22 11:29:42 +0700 add submodules: graphql and toml-serialization`. $ rm -f build/all_tests && make ENABLE_EVMC=1 test $ ulimit -S -s 16384 # Requires larger stack than default to avoid crash. $ ./build/all_tests 9 | tee tlog [Suite] persist block json tests ... Stack range 38416 depthHigh 3 ... Stack range 13074720 depthHigh 1024 [OK] tests/fixtures/PersistBlockTests/block1431916.json These tests use 13.07 MB of stack to run, and so crash with the default stack limit on Ubuntu Server 20.04 (8MB). Exactly 12768 bytes per EVM call stack frame. $ rm -f build/all_tests && make ENABLE_EVMC=1 test $ ulimit -S -s 16384 # Requires larger stack than default. $ ./build/all_tests 7 | tee tlog [Suite] new generalstate json tests ... Stack range 14384 depthHigh 2 ... Stack range 3495456 depthHigh 457 [OK] tests/fixtures/eth_tests/GeneralStateTests/stRandom2/randomStatetest639.json ... Stack range 3709600 depthHigh 485 [OK] tests/fixtures/eth_tests/GeneralStateTests/stRandom2/randomStatetest458.json ... Stack range 7831600 depthHigh 1024 [OK] tests/fixtures/eth_tests/GeneralStateTests/stCreate2/Create2OnDepth1024.json These tests use 7.83MB of stack to run. About 7648 bytes per EVM call stack frame. It _only just_ avoids crashing with the default Ubuntu Server stack limit of 8 MB. However, it still crashes on Windows x86-64, which is why the Windows CI EVMC target is currently disabled. On Linux where this passes, this is so borderline that it affects work and testing of the complex storage code, because that's called from the EVM. Also, this greatly exceeds the default thread stack size. Measurements after ================== $ rm -f build/all_tests && make ENABLE_EVMC=1 test $ ulimit -S -s 600 # Because we can! 600k stack. $ ./build/all_tests 9 | tee tlog [Suite] persist block json tests ... Stack range 1936 depthHigh 3 ... Stack range 556272 depthHigh 1022 Stack range 556512 depthHigh 1023 Stack range 556816 depthHigh 1023 Stack range 557056 depthHigh 1024 Stack range 557360 depthHigh 1024 [OK] tests/fixtures/PersistBlockTests/block1431916.json $ rm -f build/all_tests && make ENABLE_EVMC=1 test $ ulimit -S -s 600 # Because we can! 600k stack. $ ./build/all_tests 7 | tee tlog [Suite] new generalstate json tests ... Stack range 1392 depthHigh 2 ... Stack range 248912 depthHigh 457 [OK] tests/fixtures/eth_tests/GeneralStateTests/stRandom2/randomStatetest639.json ... Stack range 264144 depthHigh 485 [OK] tests/fixtures/eth_tests/GeneralStateTests/stRandom2/randomStatetest458.json ... Stack range 557360 depthHigh 1024 [OK] tests/fixtures/eth_tests/GeneralStateTests/stStaticCall/static_CallRecursiveBombPreCall.json For both tests, a satisfying *544 bytes* per EVM call stack frame, and EVM takes less than 600 kB total. With other overheads, both tests run in 600 kB stack total at maximum EVM depth. We must add some headroom on this for database activity called from the EVM, and different compile targets. But it means the EVM itself is no longer a stack burden. This is much smaller than the default thread stack size on Linux (2MB), with plenty of margin. (Just fyi, it isn't smaller than a _small_ thread stack on Linux from a long time ago (128kB), and some small embedded C targets.) This size is well suited to running EVMs in threads. Further reduction ================= This patch solves the stack problem. Windows and Linux 64-bit EVMC CI targets can be re-enabled, and there is no longer a problem with stack usage. We can reduce further to ~340 bytes per frame and 350 kB total, while still complying with EVMC. But as this involves changing how errors are handled to comply fully with EVMC, and removing `dispose` calls, it's not worth doing now while there are other EVMC changes in progress that will have the same effect. A Nimbus-specific extension will allow us to avoid recursion with EVMC anyway, bringing bytes per frame to zero. We need the extension anyway, to support Chronos `async` which parallel transaction processing is built around. Interop with non-Nimbus over EVMC won't let us avoid recursion, but then we can't control the stack frame size either. To prevent stack overflow in interop I anticipate using (this method in Aleth) [https://github.com/ethereum/aleth/blob/6e96ce34e3f131e2d42f3cb00741b54e05ab029d/libethereum/ExtVM.cpp#L61]. Smoke test other versions of GCC and Clang/LLVM =============================================== As all builds including Windows use GCC or Apple's Clang/LLVM, this is just to verify we're in the right ballpark on all targets. I've only checked `x86_64` though, not 32-bit, and not ARM. It's interesting to see GCC 10 uses less stack. This is because it optimises `struct` returns better, sometimes skipping an intermediate copy. Here it benefits the EVMC API, but I found GCC 10 also improves the larger stack usage of the rest of `nimbus-eth1` as well. Apple clang 12.0.0 (clang-1200.0.26.2) on MacOS 10.15: - 544 bytes per EVM call stack frame GCC 10.3.0 (Ubuntu 10.3.0-1ubuntu1) on Ubuntu 21.04: - 464 bytes per EVM call stack frame GCC 10.2.0 (Ubuntu 10.2.0-5ubuntu1~20.04) on Ubuntu 20.04 LTS: - 464 bytes per EVM call stack frame GCC 11.0.1 20210417 (experimental; Ubuntu 11-20210417-1ubuntu1) on Ubuntu 21.04: - 8 bytes per EVM call stack frame GCC 9.3.0 (Ubuntu 9.3.0-17ubuntu1~20.04) on Ubuntu 20.04 LTS: - 544 bytes per EVM call stack frame GCC 8.4.0 (Ubuntu 8.4.0-3ubuntu2) on Ubuntu 20.04 LTS: - 544 bytes per EVM call stack frame GCC 7.5.0 (Ubuntu 7.5.0-6ubuntu2) on Ubuntu 20.04 LTS: - 544 bytes per EVM call stack frame GCC 9.2.1 20191008 (Ubuntu 9.2.1-9ubuntu2) on Ubuntu 19.10: - 528 bytes per EVM call stack frame Signed-off-by: Jamie Lokier <jamie@shareable.org>
2021-04-26 15:01:00 +00:00
when defined(evmc_enabled):
child*: ref nimbus_message
res*: nimbus_result
else:
parent*, child*: Computation
EVM: Small patch that reduces EVM stack usage to almost nothing There's been a lot of talk about the Nimbus EVM "stack problem". I think we assumed changing it would require big changes to the interpreter code, touching a lot of functions. It turned out to be a low hanging fruit. This patch solves the stack problem, but hardly touches anything. The change in EVM stack memory is from 13 MB worst case to just 48 kB, a 250x reduction. I've been doing work on the database/storage/trie code. While looking at the API between the EVM and the database/storage/trie, this stack patch stood out and made itself obvious. As it's tiny, rather than more talk, here it is. Note: This patch is intentionally small, non-invasive, and hopefully easy to understand, so that it doesn't conflict with other work done on the EVM, and can easily be grafted into any other EVM structure. Motivation ========== - We run out of space and crash on some targets, unless the stack limit is raised above its default. Surprise segmentation faults are unhelpful. - Some CI targets have been disabled for months due to this. - Because usage borders on the system limits, when working on database/storage/trie/sync code (called from the EVM), segmentation faults occur and are misleading. They cause lost time due to thinking there's a crash bug in the code being worked on, when there's nothing wrong with it. - Sometimes unrelated, trivial code changes elsewhere trigger CI test failures. It looks like abrupt termination. A simple, recent patch was crashing in `make test` even though it was a trivial refactor. Turns out it pushed the stack over the edge. - A large stack has to be scanned by the Nim garbage collector sometimes. Larger stack means slower GC and memory allocation. - The structure of this small patch suggests how to weave async into the EVM with almost no changes to the EVM, and no async transformation overhead. - The patch seemed obvious when working on the API between EVM and storage. Measurements before =================== All these tests were run on Ubuntu 20.04 server, x86-64. This is one of the targets that has been disabled for a while in CI in EVMC mode due to crashing, and excessive stack usage is the cause. Testing commit 0c34a8e3 `2021-04-08 17:46:00 +0200 CI: use MSYS2 on Windows`. $ rm -f build/all_tests && make ENABLE_EVMC=1 test $ ulimit -S -s 16384 # Requires larger stack than default to avoid crash. $ ./build/all_tests 9 | tee tlog [Suite] persist block json tests ... Stack range 38496 depthHigh 3 ... Stack range 13140272 depthHigh 1024 [OK] tests/fixtures/PersistBlockTests/block1431916.json These tests use 13.14 MB of stack to run, and so crash with the default stack limit on Ubuntu Server 20.04 (8MB). Exactly 12832 bytes per EVM call stack frame. It's interesting to see some stack frames take a bit more. $ rm -f build/all_tests && make ENABLE_EVMC=1 test $ ulimit -S -s 16384 # Requires larger stack than default. $ ./build/all_tests 7 | tee tlog [Suite] new generalstate json tests ... Stack range 15488 depthHigh 2 ... Stack range 3539312 depthHigh 457 [OK] tests/fixtures/eth_tests/GeneralStateTests/stRandom2/randomStatetest639.json ... Stack range 3756144 depthHigh 485 [OK] tests/fixtures/eth_tests/GeneralStateTests/stRandom2/randomStatetest458.json ... Stack range 7929968 depthHigh 1024 [OK] tests/fixtures/eth_tests/GeneralStateTests/stCreate2/Create2OnDepth1024.json These tests use 7.92MB of stack to run. About 7264 bytes per EVM call stack frame. It _only just_ avoids crashing with the default Ubuntu Server stack limit of 8 MB. However, it still crashes on Windows x86-64, which is why the CI target is currently disabled. On Linux where this passes, this is so borderline that it affects work and testing of storage and sync code, because that's called from the EVM. Which was a motivation for dealing with the stack instead of letting this linger. Also, this stack greatly exceeds the default thread stack size. $ rm -f build/all_tests && make ENABLE_EVMC=0 test $ ulimit -S -s 16384 # Requires larger stack than default to avoid crash. $ ./build/all_tests 9 | tee tlog [Suite] persist block json tests ... Stack range 33216 depthHigh 3 ... Stack range 11338032 depthHigh 1024 [OK] tests/fixtures/PersistBlockTests/block1431916.json These tests use 11.33 MB stack to run, and so crash with a default stack limit of 8MB. Exactly 11072 bytes per EVM call stack frame. It's interesting to see some stack frames take a bit more. $ rm -f build/all_tests && make ENABLE_EVMC=0 test $ ulimit -S -s 16384 # Requires larger stack than default. $ ./build/all_tests 7 | tee tlog [Suite] new generalstate json tests ... Stack range 10224 depthHigh 2 ... Stack range 2471760 depthHigh 457 [OK] tests/fixtures/eth_tests/GeneralStateTests/stRandom2/randomStatetest639.json ... Stack range 2623184 depthHigh 485 [OK] tests/fixtures/eth_tests/GeneralStateTests/stRandom2/randomStatetest458.json ... Stack range 5537824 depthHigh 1024 [OK] tests/fixtures/eth_tests/GeneralStateTests/stCreate2/Create2OnDepth1024.json These tests use 5.54 MB of stack to run, and avoid crashing on with a default stack limit of 8 MB. About 5408 bytes per EVM call stack frame. However, this is uncomfortably close to the limit, as the stack frame size is sensitive to changes in the code. Also, this stack greatly exceeds the default thread stack size. Measurements after ================== (This patch doesn't address EVMC mode, which is not our default. EVMC stack usage remains about the same. EVMC mode is addressed in another tiny patch.) $ rm -f build/all_tests && make ENABLE_EVMC=0 test $ ulimit -S -s 80 # Because we can! 80k stack. $ ./build/all_tests 9 | tee tlog [Suite] persist block json tests ... Stack range 496 depthHigh 3 ... Stack range 49504 depthHigh 1024 [OK] tests/fixtures/PersistBlockTests/block1431916.json $ rm -f build/all_tests && make ENABLE_EVMC=0 test $ ulimit -S -s 72 # Because we can! 72k stack. $ ./build/all_tests 7 | tee tlog [Suite] new generalstate json tests ... Stack range 448 depthHigh 2 ... Stack range 22288 depthHigh 457 [OK] tests/fixtures/eth_tests/GeneralStateTests/stRandom2/randomStatetest639.json ... Stack range 23632 depthHigh 485 [OK] tests/fixtures/eth_tests/GeneralStateTests/stRandom2/randomStatetest458.json ... Stack range 49504 depthHigh 1024 [OK] tests/fixtures/eth_tests/GeneralStateTests/stCreate2/Create2OnDepth1024.json For both tests, a satisfying *48 bytes* per EVM call stack frame, and EVM takes not much more than 48 kB. With other overheads, both tests run in 80 kB stack total at maximum EVM depth. We must add some headroom on this for database activity called from the EVM, and different compile targets. But it means the EVM itself is no longer a stack burden. This is much smaller than the default thread stack size on Linux (2MB), with plenty of margin. It's even smaller than Linux from a long time ago (128kB), and some small embedded C targets. (Just fyi, though, some JVM environments allocated just 32 kB to thread stacks.) This size is also well suited to running EVMs in threads, if that's useful. Subtle exception handling and `dispose` ======================================= It is important that each `snapshot` has a corresponding `dispose` in the event of an exception being raised. This code does do that, but in a subtle way. The pair of functions `execCallOrCreate` and `execCallOrCreateAux` are equivalent to the following code, where you can see `dispose` more clearly: proc execCallOrCreate*(c: Computation) = defer: c.dispose() if c.beforeExec(): return c.executeOpcodes() while not c.continuation.isNil: c.child.execCallOrCreate() c.child = nil (c.continuation)() c.executeOpcodes() c.afterExec() That works fine, but only reduces the stack used to 300-700 kB instead of 48 kB. To get lower we split the above into separate `execCallOrCreate` and `execCallOrCreateAux`. Only the outermost has `defer`, and instead of handling one level, it walks the entire `c.parent` chain calling `dispose` if needed. The inner one avoids `defer`, which greatly reduces the size of its stackframe. `c` is a `var` parameter, at each level of recursion. So the outermost proc sees the temporary changes made by all inner calls. This is why `c` is updated and the `c.parent` chain is maintained at each step. Signed-off-by: Jamie Lokier <jamie@shareable.org>
2021-04-12 17:06:31 +00:00
continuation*: proc() {.gcsafe.}
Error* = ref object
info*: string
burnsGas*: bool
GasMeter* = object
gasRefunded*: GasInt
gasRemaining*: GasInt
CallKind* = enum
evmcCall = 0, # CALL
evmcDelegateCall = 1, # DELEGATECALL
evmcCallCode = 2, # CALLCODE
evmcCreate = 3, # CREATE
evmcCreate2 = 4 # CREATE2
MsgFlags* = enum
emvcNoFlags = 0
emvcStatic = 1
Message* = ref object
kind*: CallKind
depth*: int
gas*: GasInt
sender*: EthAddress
contractAddress*: EthAddress
codeAddress*: EthAddress
value*: UInt256
data*: seq[byte]
flags*: MsgFlags