discard """
batchable: false
"""
#
#
# Nim's Runtime Library
# (c) Copyright 2018 Nim Contributors
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
# This is the Nim hot code reloading run-time for the native targets.
#
# This minimal dynamic library is not subject to reloading when the
# `hotCodeReloading` build mode is enabled. It's responsible for providing
# a permanent memory location for all globals and procs within a program
# and orchestrating the reloading. For globals, this is easily achieved
# by storing them on the heap. For procs, we produce on the fly simple
# trampolines that can be dynamically overwritten to jump to a different
# target. In the host program, all globals and procs are first registered
# here with `hcrRegisterGlobal` and `hcrRegisterProc` and then the
# returned permanent locations are used in every reference to these symbols
# onwards.
#
# Detailed description:
#
# When code is compiled with the hotCodeReloading option for native targets
# a couple of things happen for all modules in a project:
# - the useNimRtl option is forced (including when building the HCR runtime too)
# - all modules of a target get built into separate shared libraries
# - the smallest granularity of reloads is modules
# - for each .c (or .cpp) in the corresponding nimcache folder of the project
# a shared object is built with the name of the source file + DLL extension
# - only the main module produces whatever the original project type intends
# (again in nimcache) and is then copied to its original destination
# - linking is done in parallel - just like compilation
# - function calls to functions from the same project go through function pointers:
# - with a few exceptions - see the nonReloadable pragma
# - the forward declarations of the original functions become function
# pointers as static globals with the same names
# - the original function definitions get suffixed with <name>_actual
# - the function pointers get initialized with the address of the corresponding
# function in the DatInit of their module through a call to either hcrRegisterProc
# or hcrGetProc. When being registered, the <name>_actual address is passed to
# hcrRegisterProc and a permanent location is returned and assigned to the pointer.
# This way the implementation (<name>_actual) can change but the address for it
# will be the same - this works by just updating a jump instruction (trampoline).
# For functions from other modules hcrGetProc is used (after they are registered).
# - globals are initialized only once and their state is preserved
# - including locals with the {.global.} pragma
# - their definitions are changed into pointer definitions which are initialized
# in the DatInit() of their module with calls to hcrRegisterGlobal (supplying the
# size of the type that this HCR runtime should allocate) and a bool is returned
# which when true triggers the initialization code for the global (only once).
# Globals from other modules: a global pointer coupled with a hcrGetGlobal call.
# - globals which have already been initialized cannot have their values changed
# by changing their initialization - use a handler or some other mechanism
# - new globals can be introduced when reloading
# - top-level code (global scope) is executed only once - at the first module load
# - the runtime knows every symbol's module owner (globals and procs)
# - both the RTL and HCR shared libraries need to be near the program for execution
# - same folder, in the PATH or LD_LIBRARY_PATH env var, etc (depending on OS)
# - the main module is responsible for initializing the HCR runtime
# - the main module loads the RTL and HCR shared objects
# - after that a call to hcrInit() is done in the main module which triggers
# the loading of all modules the main one imports, and doing that for the
# dependencies of each module recursively. Basically a DFS traversal.
# - then initialization takes place with several passes over all modules:
# - HcrInit - initializes the pointers for HCR procs such as hcrRegisterProc
# - HcrCreateTypeInfos - creates globals which will be referenced in the next pass
# - DatInit - usual dat init + register/get procs and get globals
# - Init - it does the following multiplexed operations:
# - register globals (if already registered - then just retrieve pointer)
# - execute top level scope (only if loaded for the first time)
# - when modules are loaded the originally built shared libraries get copied in
# the same folder and the copies are loaded instead of the original files
# - a module import tree is built in the runtime (and maintained when reloading)
# - hcrPerformCodeReload
# - named `performCodeReload`, requires the hotcodereloading module
# - explicitly called by the user - the current active callstack shouldn't contain
# any functions which are defined in modules that will be reloaded (or crash!).
# The reason is that old dynamic libraries get unloaded.
# Example:
# if A is the main module and it imports B, then only B is reloadable and only
# if when calling hcrPerformCodeReload there is no function defined in B in the
# current active callstack at the point of the call (it has to be done from A)
# - for reloading to take place the user has to have rebuilt parts of the application
# without changes affecting the main module in any way - it shouldn't be rebuilt.
# - to determine what needs to be reloaded the runtime starts traversing the import
# tree from the root and checks the timestamps of the loaded shared objects
# - modules that are no longer referenced are unloaded and cleaned up properly
# - symbols (procs/globals) that have been removed in the code are also cleaned up
# - so changing the init of a global does nothing, but removing it, reloading,
# and then re-introducing it with a new initializer works
# - new modules can be imported, and imports can also be reodereded/removed
# - hcrReloadNeeded() can be used to determine if any module needs reloading
# - named `hasAnyModuleChanged`, requires the hotcodereloading module
# - code in the beforeCodeReload/afterCodeReload handlers is executed on each reload
# - require the hotcodereloading module
# - such handlers can be added and removed
# - before each reload all "beforeCodeReload" handlers are executed and after
# that all handlers (including "after") from the particular module are deleted
# - the order of execution is the same as the order of top-level code execution.
# Example: if A imports B which imports C, then all handlers in C will be executed
# first (from top to bottom) followed by all from B and lastly all from A
# - after the reload all "after" handlers are executed the same way as "before"
# - the handlers for a reloaded module are always removed when reloading and then
# registered when the top-level scope is executed (thanks to `executeOnReload`)
#
# TODO next:
#
# - implement the before/after handlers and hasModuleChanged for the javascript target
# - ARM support for the trampolines
# - investigate:
# - soon the system module might be importing other modules - the init order...?
# (revert https://github.com/nim-lang/Nim/pull/11971 when working on this)
# - rethink the closure iterators
# - ability to keep old versions of dynamic libraries alive
# - because of async server code
# - perhaps with refcounting of .dlls for unfinished closures
# - linking with static libs
# - all shared objects for each module will (probably) have to link to them
# - state in static libs gets duplicated
# - linking is slow and therefore iteration time suffers
# - have just a single .dll for all .nim files and bulk reload?
# - think about the compile/link/passc/passl/emit/injectStmt pragmas
# - if a passc pragma is introduced (either written or dragged in by a new
# import) the whole command line for compilation changes - for example:
# winlean.nim: {.passc: "-DWIN32_LEAN_AND_MEAN".}
# - play with plugins/dlls/lfIndirect/lfDynamicLib/lfExportLib - shouldn't add an extra '*'
# - everything thread-local related
# - tests
# - add a new travis build matrix entry which builds everything with HCR enabled
# - currently building with useNimRtl is problematic - lots of problems...
# - how to supply the nimrtl/nimhcr shared objects to all test binaries...?
# - think about building to C++ instead of only to C - added type safety
# - run tests through valgrind and the sanitizers!
#
# TODO - nice to have cool stuff:
#
# - separate handling of global state for much faster reloading and manipulation
# - imagine sliders in an IDE for tweaking variables
# - perhaps using shared memory
# - multi-dll projects - how everything can be reloaded..?
# - a single HCR instance shared across multiple .dlls
# - instead of having to call hcrPerformCodeReload from a function in each dll
# - which currently renders the main module of each dll not reloadable
# - ability to check with the current callstack if a reload is "legal"
# - if it is in any function which is in a module about to be reloaded ==> error
# - pragma annotations for files - to be excluded from dll shenanigans
# - for such file-global pragmas look at codeReordering or injectStmt
# - how would the initialization order be kept? messy...
# - C code calling stable exportc interface of nim code (for bindings)
# - generate proxy functions with the stable names
# - in a non-reloadable part (the main binary) that call the function pointers
# - parameter passing/forwarding - how? use the same trampoline jumping?
# - extracting the dependencies for these stubs/proxies will be hard...
# - changing memory layout of types - detecting this..?
# - implement with registerType() call to HCR runtime...?
# - and checking if a previously registered type matches
# - issue an error
# - or let the user handle this by transferring the state properly
# - perhaps in the before/afterCodeReload handlers
# - implement executeOnReload for global vars too - not just statements (and document!)
# - cleanup at shutdown - freeing all globals
# - fallback mechanism if the program crashes (the program should detect crashes
# by itself using SEH/signals on Windows/Unix) - should be able to revert to
# previous versions of the .dlls by calling some function from HCR
# - improve runtime performance - possibilities
# - implement a way for multiple .nim files to be bundled into the same dll
# and have all calls within that domain to use the "_actual" versions of
# procs so there are no indirections (or the ability to just bundle everything
# except for a few unreloadable modules into a single mega reloadable dll)
# - try to load the .dlls at specific addresses of memory (close to each other)
# allocated with execution flags - check this: https://github.com/fancycode/MemoryModule
#
# TODO - unimportant:
#
# - have a "bad call" trampoline that all no-longer-present functions are routed to call there
# - so the user gets some error msg if he calls a dangling pointer instead of a crash
# - before/afterCodeReload and hasModuleChanged should be accessible only where appropriate
# - nim_program_result is inaccessible in HCR mode from external C code (see nimbase.h)
# - proper .json build file - but the format is different... multiple link commands...
# - avoid registering globals on each loop when using an iterator in global scope
#
# TODO - REPL:
# - proper way (as proposed by Zahary):
# - parse the input code and put everything in global scope except for
# statements with side effects only - those go in afterCodeReload blocks
# - my very hacky idea: just append to a closure iterator the new statements
# followed by a yield statement. So far I can think of 2 problems:
# - import and some other code cannot be written inside of a proc -
# has to be parsed and extracted in the outer scope
# - when new variables are created they are actually locals to the closure
# so the struct for the closure state grows in memory, but it has already
# been allocated when the closure was created with the previous smaller size.
# That would lead to working with memory outside of the initially allocated
# block. Perhaps something can be done about this - some way of re-allocating
# the state and transferring the old...
when defined(nimPreviewSlimSystem):
import std/assertions
when not defined(js) and (defined(hotcodereloading) or
defined(createNimHcr) or
defined(testNimHcr)):
const
dllExt = when defined(windows): "dll"
elif defined(macosx): "dylib"
else: "so"
type
HcrProcGetter* = proc (libHandle: pointer, procName: cstring): pointer {.nimcall.}
HcrGcMarkerProc = proc () {.nimcall, raises: [].}
HcrModuleInitializer* = proc () {.nimcall.}
when defined(createNimHcr):
when system.appType != "lib":
{.error: "This file has to be compiled as a library!".}
import os, tables, sets, times, strutils, reservedmem, dynlib
template trace(args: varargs[untyped]) =
when defined(testNimHcr) or defined(traceHcr):
echo args
proc sanitize(arg: Time): string =
when defined(testNimHcr): return "<time>"
else: return $arg
proc sanitize(arg: string|cstring): string =
when defined(testNimHcr): return ($arg).splitFile.name.splitFile.name
else: return $arg
{.pragma: nimhcr, compilerproc, exportc, dynlib.}
# XXX these types are CPU specific and need ARM etc support
type
ShortJumpInstruction {.packed.} = object
opcode: byte
offset: int32
LongJumpInstruction {.packed.} = object
opcode1: byte
opcode2: byte
offset: int32
absoluteAddr: pointer
proc writeJump(jumpTableEntry: ptr LongJumpInstruction, targetFn: pointer) =
let
jumpFrom = jumpTableEntry.shift(sizeof(ShortJumpInstruction))
jumpDistance = distance(jumpFrom, targetFn)
if abs(jumpDistance) < 0x7fff0000:
let shortJump = cast[ptr ShortJumpInstruction](jumpTableEntry)
shortJump.opcode = 0xE9 # relative jump
shortJump.offset = int32(jumpDistance)
else:
jumpTableEntry.opcode1 = 0xff # indirect absolute jump
jumpTableEntry.opcode2 = 0x25
when hostCPU == "i386":
# on x86 we write the absolute address of the following pointer
jumpTableEntry.offset = cast[int32](addr jumpTableEntry.absoluteAddr)
else:
# on x64, we use a relative address for the same location
jumpTableEntry.offset = 0
jumpTableEntry.absoluteAddr = targetFn
if hostCPU == "arm":
const jumpSize = 8
elif hostCPU == "arm64":
const jumpSize = 16
const defaultJumpTableSize = case hostCPU
of "i386": 50
of "amd64": 500
else: 50
let jumpTableSizeStr = getEnv("HOT_CODE_RELOADING_JUMP_TABLE_SIZE")
let jumpTableSize = if jumpTableSizeStr.len > 0: parseInt(jumpTableSizeStr)
else: defaultJumpTableSize
# TODO: perhaps keep track of free slots due to removed procs using a free list
var jumpTable = ReservedMemSeq[LongJumpInstruction].init(
memStart = cast[pointer](0x10000000),
maxLen = jumpTableSize * 1024 * 1024 div sizeof(LongJumpInstruction),
accessFlags = memExecReadWrite)
type
ProcSym = object
jump: ptr LongJumpInstruction
gen: int
GlobalVarSym = object
p: pointer
markerProc: HcrGcMarkerProc
gen: int
ModuleDesc = object
procs: Table[string, ProcSym]
globals: Table[string, GlobalVarSym]
imports: seq[string]
handle: LibHandle
hash: string
gen: int
lastModification: Time
handlers: seq[tuple[isBefore: bool, cb: proc ()]]
proc newModuleDesc(): ModuleDesc =
result.procs = initTable[string, ProcSym]()
result.globals = initTable[string, GlobalVarSym]()
result.handle = nil
result.gen = -1
result.lastModification = low(Time)
# the global state necessary for traversing and reloading the module import tree
var modules = initTable[string, ModuleDesc]()
var root: string
var system: string
var mainDatInit: HcrModuleInitializer
var generation = 0
# necessary for queries such as "has module X changed" - contains all but the main module
var hashToModuleMap = initTable[string, string]()
# necessary for registering handlers and keeping them up-to-date
var currentModule: string
# supplied from the main module - used by others to initialize pointers to this runtime
var hcrDynlibHandle: pointer
var getProcAddr: HcrProcGetter
proc hcrRegisterProc*(module: cstring, name: cstring, fn: pointer): pointer {.nimhcr.} =
trace " register proc: ", module.sanitize, " ", name
# Please note: We must allocate a local copy of the strings, because the supplied
# `cstring` will reside in the data segment of a DLL that will be later unloaded.
let name = $name
let module = $module
var jumpTableEntryAddr: ptr LongJumpInstruction
modules[module].procs.withValue(name, p):
trace " update proc: ", name
jumpTableEntryAddr = p.jump
p.gen = generation
do:
let len = jumpTable.len
jumpTable.setLen(len + 1)
jumpTableEntryAddr = addr jumpTable[len]
modules[module].procs[name] = ProcSym(jump: jumpTableEntryAddr, gen: generation)
writeJump jumpTableEntryAddr, fn
return jumpTableEntryAddr
proc hcrGetProc*(module: cstring, name: cstring): pointer {.nimhcr.} =
trace " get proc: ", module.sanitize, " ", name
return modules[$module].procs.getOrDefault($name, ProcSym()).jump
proc hcrRegisterGlobal*(module: cstring,
name: cstring,
size: Natural,
gcMarker: HcrGcMarkerProc,
outPtr: ptr pointer): bool {.nimhcr.} =
trace " register global: ", module.sanitize, " ", name
# Please note: We must allocate local copies of the strings, because the supplied
# `cstring` will reside in the data segment of a DLL that will be later unloaded.
# Also using a ptr pointer instead of a var pointer (an output parameter)
# because for the C++ backend var parameters use references and in this use case
# it is not possible to cast an int* (for example) to a void* and then pass it
# to void*& since the casting yields an rvalue and references bind only to lvalues.
let name = $name
let module = $module
modules[module].globals.withValue(name, global):
trace " update global: ", name
outPtr[] = global.p
global.gen = generation
global.markerProc = gcMarker
return false
do:
outPtr[] = alloc0(size)
modules[module].globals[name] = GlobalVarSym(p: outPtr[],
gen: generation,
markerProc: gcMarker)
return true
proc hcrGetGlobal*(module: cstring, name: cstring): pointer {.nimhcr.} =
trace " get global: ", module.sanitize, " ", name
return modules[$module].globals[$name].p
proc getListOfModules(cstringArray: ptr pointer): seq[string] =
var curr = cast[ptr cstring](cstringArray)
while len(curr[]) > 0:
result.add($curr[])
curr = cast[ptr cstring](cast[int64](curr) + sizeof(ptr cstring))
template cleanup(collection, body) =
var toDelete: seq[string]
for name, data in collection.pairs:
if data.gen < generation:
toDelete.add(name)
trace "HCR Cleaning ", astToStr(collection), " :: ", name, " ", data.gen
for name {.inject.} in toDelete:
body
proc cleanupGlobal(module: string, name: string) =
var g: GlobalVarSym
if modules[module].globals.take(name, g):
dealloc g.p
proc cleanupSymbols(module: string) =
cleanup modules[module].globals:
cleanupGlobal(module, name)
cleanup modules[module].procs:
modules[module].procs.del(name)
proc unloadDll(name: string) =
if modules[name].handle != nil:
unloadLib(modules[name].handle)
proc loadDll(name: cstring) {.nimhcr.} =
let name = $name
trace "HCR LOADING: ", name.sanitize
if modules.contains(name):
unloadDll(name)
else:
modules[name] = newModuleDesc()
let copiedName = name & ".copy." & dllExt
copyFileWithPermissions(name, copiedName)
let lib = loadLib(copiedName)
assert lib != nil
modules[name].handle = lib
modules[name].gen = generation
modules[name].lastModification = getLastModificationTime(name)
# update the list of imports by the module
let getImportsProc = cast[proc (): ptr pointer {.nimcall.}](
checkedSymAddr(lib, "HcrGetImportedModules"))
modules[name].imports = getListOfModules(getImportsProc())
# get the hash of the module
let getHashProc = cast[proc (): cstring {.nimcall.}](
checkedSymAddr(lib, "HcrGetSigHash"))
modules[name].hash = $getHashProc()
hashToModuleMap[modules[name].hash] = name
# Remove handlers for this module if reloading - they will be re-registered.
# In order for them to be re-registered we need to de-register all globals
# that trigger the registering of handlers through calls to hcrAddEventHandler
modules[name].handlers.setLen(0)
proc initHcrData(name: cstring) {.nimhcr.} =
trace "HCR Hcr init: ", name.sanitize
cast[proc (h: pointer, gpa: HcrProcGetter) {.nimcall.}](
checkedSymAddr(modules[$name].handle, "HcrInit000"))(hcrDynlibHandle, getProcAddr)
proc initTypeInfoGlobals(name: cstring) {.nimhcr.} =
trace "HCR TypeInfo globals init: ", name.sanitize
cast[HcrModuleInitializer](checkedSymAddr(modules[$name].handle, "HcrCreateTypeInfos"))()
proc initPointerData(name: cstring) {.nimhcr.} =
trace "HCR Dat init: ", name.sanitize
cast[HcrModuleInitializer](checkedSymAddr(modules[$name].handle, "DatInit000"))()
proc initGlobalScope(name: cstring) {.nimhcr.} =
trace "HCR Init000: ", name.sanitize
# set the currently inited module - necessary for registering the before/after HCR handlers
currentModule = $name
cast[HcrModuleInitializer](checkedSymAddr(modules[$name].handle, "Init000"))()
var modulesToInit: seq[string] = @[]
var allModulesOrderedByDFS: seq[string] = @[]
proc recursiveDiscovery(dlls: seq[string]) =
for curr in dlls:
if modules.contains(curr):
# skip updating modules that have already been updated to the latest generation
if modules[curr].gen >= generation:
trace "HCR SKIP: ", curr.sanitize, " gen is already: ", modules[curr].gen
continue
# skip updating an unmodified module but continue traversing its dependencies
if modules[curr].lastModification >= getLastModificationTime(curr):
trace "HCR SKIP (not modified): ", curr.sanitize, " ", modules[curr].lastModification.sanitize
# update generation so module doesn't get collected
modules[curr].gen = generation
# recurse to imported modules - they might be changed
recursiveDiscovery(modules[curr].imports)
allModulesOrderedByDFS.add(curr)
continue
loadDll(curr.cstring)
# first load all dependencies of the current module and init it after that
recursiveDiscovery(modules[curr].imports)
allModulesOrderedByDFS.add(curr)
modulesToInit.add(curr)
proc initModules() =
# first init the pointers to hcr functions and also do the registering of typeinfo globals
for curr in modulesToInit:
initHcrData(curr.cstring)
initTypeInfoGlobals(curr.cstring)
# for now system always gets fully inited before any other module (including when reloading)
initPointerData(system.cstring)
initGlobalScope(system.cstring)
# proceed with the DatInit calls - for all modules - including the main one!
for curr in allModulesOrderedByDFS:
if curr != system:
initPointerData(curr.cstring)
mainDatInit()
# execute top-level code (in global scope)
for curr in modulesToInit:
if curr != system:
initGlobalScope(curr.cstring)
# cleanup old symbols which are gone now
for curr in modulesToInit:
cleanupSymbols(curr)
proc hcrInit*(moduleList: ptr pointer, main, sys: cstring,
datInit: HcrModuleInitializer, handle: pointer, gpa: HcrProcGetter) {.nimhcr.} =
trace "HCR INITING: ", main.sanitize, " gen: ", generation
# initialize globals
root = $main
system = $sys
mainDatInit = datInit
hcrDynlibHandle = handle
getProcAddr = gpa
# the root is already added and we need it because symbols from it will also be registered in the HCR system
modules[root].imports = getListOfModules(moduleList)
modules[root].gen = high(int) # something huge so it doesn't get collected
# recursively initialize all modules
recursiveDiscovery(modules[root].imports)
initModules()
# the next module to be inited will be the root
currentModule = root
proc hcrHasModuleChanged*(moduleHash: string): bool {.nimhcr.} =
let module = hashToModuleMap[moduleHash]
return modules[module].lastModification < getLastModificationTime(module)
proc hcrReloadNeeded*(): bool {.nimhcr.} =
for hash, _ in hashToModuleMap:
if hcrHasModuleChanged(hash):
return true
return false
proc hcrPerformCodeReload*() {.nimhcr.} =
if not hcrReloadNeeded():
trace "HCR - no changes"
return
# We disable the GC during the reload, because the reloading procedures
# will replace type info objects and GC marker procs. This seems to create
# problems when the GC is executed while the reload is underway.
# Future versions of NIMHCR won't use the GC, because all globals and the
# metadata needed to access them will be placed in shared memory, so they
# can be manipulated from external programs without reloading.
GC_disable()
defer: GC_enable()
inc(generation)
trace "HCR RELOADING: ", generation
var traversedHandlerModules = initHashSet[string]()
proc recursiveExecuteHandlers(isBefore: bool, module: string) =
# do not process an already traversed module
if traversedHandlerModules.containsOrIncl(module): return
traversedHandlerModules.incl module
# first recurse to do a DFS traversal
for curr in modules[module].imports:
recursiveExecuteHandlers(isBefore, curr)
# and then execute the handlers - from leaf modules all the way up to the root module
for curr in modules[module].handlers:
if curr.isBefore == isBefore:
curr.cb()
# first execute the before reload handlers
traversedHandlerModules.clear()
recursiveExecuteHandlers(true, root)
# do the reloading
modulesToInit = @[]
allModulesOrderedByDFS = @[]
recursiveDiscovery(modules[root].imports)
initModules()
# execute the after reload handlers
traversedHandlerModules.clear()
recursiveExecuteHandlers(false, root)
# collecting no longer referenced modules - based on their generation
cleanup modules:
cleanupSymbols(name)
unloadDll(name)
hashToModuleMap.del(modules[name].hash)
modules.del(name)
proc hcrAddEventHandler*(isBefore: bool, cb: proc ()) {.nimhcr.} =
modules[currentModule].handlers.add(
(isBefore: isBefore, cb: cb))
proc hcrAddModule*(module: cstring) {.nimhcr.} =
if not modules.contains($module):
modules[$module] = newModuleDesc()
proc hcrGeneration*(): int {.nimhcr.} =
generation
proc hcrMarkGlobals*() {.compilerproc, exportc, dynlib, nimcall, gcsafe.} =
# This is gcsafe, because it will be registered
# only in the GC of the main thread.
{.gcsafe.}:
for _, module in modules:
for _, global in module.globals:
if global.markerProc != nil:
global.markerProc()
elif defined(hotcodereloading) or defined(testNimHcr):
when not defined(js):
const
nimhcrLibname = when defined(windows): "nimhcr." & dllExt
elif defined(macosx): "libnimhcr." & dllExt
else: "libnimhcr." & dllExt
{.pragma: nimhcr, compilerproc, importc, dynlib: nimhcrLibname.}
proc hcrRegisterProc*(module: cstring, name: cstring, fn: pointer): pointer {.nimhcr.}
proc hcrGetProc*(module: cstring, name: cstring): pointer {.nimhcr.}
proc hcrRegisterGlobal*(module: cstring, name: cstring, size: Natural,
gcMarker: HcrGcMarkerProc, outPtr: ptr pointer): bool {.nimhcr.}
proc hcrGetGlobal*(module: cstring, name: cstring): pointer {.nimhcr.}
proc hcrInit*(moduleList: ptr pointer,
main, sys: cstring,
datInit: HcrModuleInitializer,
handle: pointer,
gpa: HcrProcGetter) {.nimhcr.}
proc hcrAddModule*(module: cstring) {.nimhcr.}
proc hcrHasModuleChanged*(moduleHash: string): bool {.nimhcr.}
proc hcrReloadNeeded*(): bool {.nimhcr.}
proc hcrPerformCodeReload*() {.nimhcr.}
proc hcrAddEventHandler*(isBefore: bool, cb: proc ()) {.nimhcr.}
proc hcrMarkGlobals*() {.raises: [], nimhcr, nimcall, gcsafe.}
when declared(nimRegisterGlobalMarker):
nimRegisterGlobalMarker(cast[GlobalMarkerProc](hcrMarkGlobals))
else:
proc hcrHasModuleChanged*(moduleHash: string): bool =
# TODO
false
proc hcrAddEventHandler*(isBefore: bool, cb: proc ()) =
# TODO
discard