error.jl
# This file is a part of Julia. License is MIT: https://julialang.org/license
# pseudo-definitions to show how everything behaves
#
# throw(label, val) = # throw a value to a dynamically enclosing block
#
# function rethrow(val)
# global current_exception = val
# throw(current_handler(), current_exception)
# end
#
# rethrow() = rethrow(current_exception)
#
# function throw(val)
# global catch_backtrace = backtrace()
# rethrow(val)
# end
"""
throw(e)
Throw an object as an exception.
"""
throw
## native julia error handling ##
"""
error(message::AbstractString)
Raise an `ErrorException` with the given message.
"""
error(s::AbstractString) = throw(ErrorException(s))
"""
error(msg...)
Raise an `ErrorException` with the given message.
"""
function error(s::Vararg{Any,N}) where {N}
@_noinline_meta
throw(ErrorException(Main.Base.string(s...)))
end
"""
rethrow()
Rethrow the current exception from within a `catch` block. The rethrown
exception will continue propagation as if it had not been caught.
!!! note
The alternative form `rethrow(e)` allows you to associate an alternative
exception object `e` with the current backtrace. However this misrepresents
the program state at the time of the error so you're encouraged to instead
throw a new exception using `throw(e)`. In Julia 1.1 and above, using
`throw(e)` will preserve the root cause exception on the stack, as
described in [`catch_stack`](@ref).
"""
rethrow() = ccall(:jl_rethrow, Bottom, ())
rethrow(@nospecialize(e)) = ccall(:jl_rethrow_other, Bottom, (Any,), e)
struct InterpreterIP
code::Union{CodeInfo,Core.MethodInstance,Nothing}
stmt::Csize_t
mod::Union{Module,Nothing}
end
# convert dual arrays (raw bt buffer, array of GC managed values) to a single
# array of locations
function _reformat_bt(bt::Array{Ptr{Cvoid},1}, bt2::Array{Any,1})
ret = Vector{Union{InterpreterIP,Ptr{Cvoid}}}()
i, j = 1, 1
while i <= length(bt)
ip = bt[i]::Ptr{Cvoid}
if UInt(ip) != (-1 % UInt) # See also jl_bt_is_native
# native frame
push!(ret, ip)
i += 1
continue
end
# Extended backtrace entry
entry_metadata = reinterpret(UInt, bt[i+1])::UInt
njlvalues = entry_metadata & 0x7
nuintvals = (entry_metadata >> 3) & 0x7
tag = (entry_metadata >> 6) & 0xf
header = entry_metadata >> 10
if tag == 1 # JL_BT_INTERP_FRAME_TAG
code = bt2[j]::Union{CodeInfo,Core.MethodInstance,Nothing}
mod = njlvalues == 2 ? bt2[j+1]::Union{Module,Nothing} : nothing
push!(ret, InterpreterIP(code, header, mod))
else
# Tags we don't know about are an error
throw(ArgumentError("Unexpected extended backtrace entry tag $tag at bt[$i]"))
end
# See jl_bt_entry_size
j += Int(njlvalues)
i += 2 + Int(njlvalues + nuintvals)
end
ret
end
"""
backtrace()
Get a backtrace object for the current program point.
"""
function backtrace()
@_noinline_meta
# skip frame for backtrace(). Note that for this to work properly,
# backtrace() itself must not be interpreted nor inlined.
skip = 1
bt1, bt2 = ccall(:jl_backtrace_from_here, Ref{SimpleVector}, (Cint, Cint), false, skip)
return _reformat_bt(bt1::Vector{Ptr{Cvoid}}, bt2::Vector{Any})
end
"""
catch_backtrace()
Get the backtrace of the current exception, for use within `catch` blocks.
"""
function catch_backtrace()
bt, bt2 = ccall(:jl_get_backtrace, Ref{SimpleVector}, ())
return _reformat_bt(bt::Vector{Ptr{Cvoid}}, bt2::Vector{Any})
end
"""
catch_stack(task=current_task(); [inclue_bt=true])
Get the stack of exceptions currently being handled. For nested catch blocks
there may be more than one current exception in which case the most recently
thrown exception is last in the stack. The stack is returned as a Vector of
`(exception,backtrace)` pairs, or a Vector of exceptions if `include_bt` is
false.
Explicitly passing `task` will return the current exception stack on an
arbitrary task. This is useful for inspecting tasks which have failed due to
uncaught exceptions.
!!! compat "Julia 1.1"
This function is experimental in Julia 1.1 and will likely be renamed in a
future release (see https://github.com/JuliaLang/julia/pull/29901).
"""
function catch_stack(task=current_task(); include_bt=true)
raw = ccall(:jl_get_excstack, Any, (Any,Cint,Cint), task, include_bt, typemax(Cint))::Vector{Any}
formatted = Any[]
stride = include_bt ? 3 : 1
for i = reverse(1:stride:length(raw))
e = raw[i]
push!(formatted, include_bt ? (e,Base._reformat_bt(raw[i+1],raw[i+2])) : e)
end
formatted
end
## keyword arg lowering generates calls to this ##
function kwerr(kw, args::Vararg{Any,N}) where {N}
@_noinline_meta
throw(MethodError(typeof(args[1]).name.mt.kwsorter, (kw,args...)))
end
## system error handling ##
"""
systemerror(sysfunc[, errno::Cint=Libc.errno()])
systemerror(sysfunc, iftrue::Bool)
Raises a `SystemError` for `errno` with the descriptive string `sysfunc` if `iftrue` is `true`
"""
systemerror(p, b::Bool; extrainfo=nothing) = b ? systemerror(p, extrainfo=extrainfo) : nothing
systemerror(p, errno::Cint=Libc.errno(); extrainfo=nothing) = throw(Main.Base.SystemError(string(p), errno, extrainfo))
## system errors from Windows API functions
struct WindowsErrorInfo
errnum::UInt32
extrainfo
end
"""
windowserror(sysfunc[, code::UInt32=Libc.GetLastError()])
windowserror(sysfunc, iftrue::Bool)
Like [`systemerror`](@ref), but for Windows API functions that use [`GetLastError`](@ref Base.Libc.GetLastError) to
return an error code instead of setting [`errno`](@ref Base.Libc.errno).
"""
windowserror(p, b::Bool; extrainfo=nothing) = b ? windowserror(p, extrainfo=extrainfo) : nothing
windowserror(p, code::UInt32=Libc.GetLastError(); extrainfo=nothing) = throw(Main.Base.SystemError(string(p), 0, WindowsErrorInfo(code, extrainfo)))
## assertion macro ##
"""
@assert cond [text]
Throw an [`AssertionError`](@ref) if `cond` is `false`. Preferred syntax for writing assertions.
Message `text` is optionally displayed upon assertion failure.
!!! warning
An assert might be disabled at various optimization levels.
Assert should therefore only be used as a debugging tool
and not used for authentication verification (e.g., verifying passwords),
nor should side effects needed for the function to work correctly
be used inside of asserts.
# Examples
```jldoctest
julia> @assert iseven(3) "3 is an odd number!"
ERROR: AssertionError: 3 is an odd number!
julia> @assert isodd(3) "What even are numbers?"
```
"""
macro assert(ex, msgs...)
msg = isempty(msgs) ? ex : msgs[1]
if isa(msg, AbstractString)
msg = msg # pass-through
elseif !isempty(msgs) && (isa(msg, Expr) || isa(msg, Symbol))
# message is an expression needing evaluating
msg = :(Main.Base.string($(esc(msg))))
elseif isdefined(Main, :Base) && isdefined(Main.Base, :string) && applicable(Main.Base.string, msg)
msg = Main.Base.string(msg)
else
# string() might not be defined during bootstrap
msg = quote
msg = $(Expr(:quote,msg))
isdefined(Main, :Base) ? Main.Base.string(msg) :
(Core.println(msg); "Error during bootstrap. See stdout.")
end
end
return :($(esc(ex)) ? $(nothing) : throw(AssertionError($msg)))
end
struct ExponentialBackOff
n::Int
first_delay::Float64
max_delay::Float64
factor::Float64
jitter::Float64
function ExponentialBackOff(n, first_delay, max_delay, factor, jitter)
all(x->x>=0, (n, first_delay, max_delay, factor, jitter)) || error("all inputs must be non-negative")
new(n, first_delay, max_delay, factor, jitter)
end
end
"""
ExponentialBackOff(; n=1, first_delay=0.05, max_delay=10.0, factor=5.0, jitter=0.1)
A [`Float64`](@ref) iterator of length `n` whose elements exponentially increase at a
rate in the interval `factor` * (1 ± `jitter`). The first element is
`first_delay` and all elements are clamped to `max_delay`.
"""
ExponentialBackOff(; n=1, first_delay=0.05, max_delay=10.0, factor=5.0, jitter=0.1) =
ExponentialBackOff(n, first_delay, max_delay, factor, jitter)
function iterate(ebo::ExponentialBackOff, state= (ebo.n, min(ebo.first_delay, ebo.max_delay)))
state[1] < 1 && return nothing
next_n = state[1]-1
curr_delay = state[2]
next_delay = min(ebo.max_delay, state[2] * ebo.factor * (1.0 - ebo.jitter + (rand(Float64) * 2.0 * ebo.jitter)))
(curr_delay, (next_n, next_delay))
end
length(ebo::ExponentialBackOff) = ebo.n
eltype(::Type{ExponentialBackOff}) = Float64
"""
retry(f; delays=ExponentialBackOff(), check=nothing) -> Function
Return an anonymous function that calls function `f`. If an exception arises,
`f` is repeatedly called again, each time `check` returns `true`, after waiting the
number of seconds specified in `delays`. `check` should input `delays`'s
current state and the `Exception`.
!!! compat "Julia 1.2"
Before Julia 1.2 this signature was restricted to `f::Function`.
# Examples
```julia
retry(f, delays=fill(5.0, 3))
retry(f, delays=rand(5:10, 2))
retry(f, delays=Base.ExponentialBackOff(n=3, first_delay=5, max_delay=1000))
retry(http_get, check=(s,e)->e.status == "503")(url)
retry(read, check=(s,e)->isa(e, IOError))(io, 128; all=false)
```
"""
function retry(f; delays=ExponentialBackOff(), check=nothing)
(args...; kwargs...) -> begin
y = iterate(delays)
while y !== nothing
(delay, state) = y
try
return f(args...; kwargs...)
catch e
y === nothing && rethrow()
if check !== nothing
result = check(state, e)
state, retry_or_not = length(result) == 2 ? result : (state, result)
retry_or_not || rethrow()
end
end
sleep(delay)
y = iterate(delays, state)
end
# When delays is out, just run the function without try/catch
return f(args...; kwargs...)
end
end
