Backports for 1.10.0-rc2

Make.inc

@@ -359,6 +359,10 @@ USE_MLIR := 0
 # Options to use RegionVectorizer
 USE_RV := 0
 
+# Use `ccache` for speeding up recompilation of the C/C++ part of Julia.
+# Requires the `ccache` executable to be in the `PATH` environment variable.
+USECCACHE := 0
+
 # Cross-compile
 #XC_HOST := i686-w64-mingw32
 #XC_HOST := x86_64-w64-mingw32

base/Base.jl

@@ -115,6 +115,12 @@ time_ns() = ccall(:jl_hrtime, UInt64, ())
 
 start_base_include = time_ns()
 
+# A warning to be interpolated in the docstring of every dangerous mutating function in Base, see PR #50824
+const _DOCS_ALIASING_WARNING = """
+!!! warning
+    Behavior can be unexpected when any mutated argument shares memory with any other argument.
+"""
+
 ## Load essential files and libraries
 include("essentials.jl")
 include("ctypes.jl")

base/abstractarray.jl

@@ -905,6 +905,8 @@ If `dst` and `src` are of the same type, `dst == src` should hold after
 the call. If `dst` and `src` are multidimensional arrays, they must have
 equal [`axes`](@ref).
 
+$(_DOCS_ALIASING_WARNING)
+
 See also [`copyto!`](@ref).
 
 !!! compat "Julia 1.1"
@@ -1369,6 +1371,8 @@ _unsafe_ind2sub(sz, i) = (@inline; _ind2sub(sz, i))
 Store values from array `X` within some subset of `A` as specified by `inds`.
 The syntax `A[inds...] = X` is equivalent to `(setindex!(A, X, inds...); X)`.
 
+$(_DOCS_ALIASING_WARNING)
+
 # Examples
 ```jldoctest
 julia> A = zeros(2,2);
@@ -1587,10 +1591,14 @@ eltypeof(x::AbstractArray) = eltype(x)
 promote_eltypeof() = error()
 promote_eltypeof(v1) = eltypeof(v1)
 promote_eltypeof(v1, vs...) = promote_type(eltypeof(v1), promote_eltypeof(vs...))
+promote_eltypeof(v1::T, vs::T...) where {T} = eltypeof(v1)
+promote_eltypeof(v1::AbstractArray{T}, vs::AbstractArray{T}...) where {T} = T
 
 promote_eltype() = error()
 promote_eltype(v1) = eltype(v1)
 promote_eltype(v1, vs...) = promote_type(eltype(v1), promote_eltype(vs...))
+promote_eltype(v1::T, vs::T...) where {T} = eltype(T)
+promote_eltype(v1::AbstractArray{T}, vs::AbstractArray{T}...) where {T} = T
 
 #TODO: ERROR CHECK
 _cat(catdim::Int) = Vector{Any}()
@@ -3339,6 +3347,8 @@ end
 Like [`map`](@ref), but stores the result in `destination` rather than a new
 collection. `destination` must be at least as large as the smallest collection.
 
+$(_DOCS_ALIASING_WARNING)
+
 See also: [`map`](@ref), [`foreach`](@ref), [`zip`](@ref), [`copyto!`](@ref).
 
 # Examples

base/abstractset.jl

@@ -65,6 +65,8 @@ const ∪ = union
 Construct the [`union`](@ref) of passed in sets and overwrite `s` with the result.
 Maintain order with arrays.
 
+$(_DOCS_ALIASING_WARNING)
+
 # Examples
 ```jldoctest
 julia> a = Set([3, 4, 5]);
@@ -182,6 +184,8 @@ const ∩ = intersect
 
 Intersect all passed in sets and overwrite `s` with the result.
 Maintain order with arrays.
+
+$(_DOCS_ALIASING_WARNING)
 """
 function intersect!(s::AbstractSet, itrs...)
     for x in itrs
@@ -218,6 +222,8 @@ setdiff(s) = union(s)
 Remove from set `s` (in-place) each element of each iterable from `itrs`.
 Maintain order with arrays.
 
+$(_DOCS_ALIASING_WARNING)
+
 # Examples
 ```jldoctest
 julia> a = Set([1, 3, 4, 5]);
@@ -272,6 +278,8 @@ symdiff(s) = symdiff!(copy(s))
 Construct the symmetric difference of the passed in sets, and overwrite `s` with the result.
 When `s` is an array, the order is maintained.
 Note that in this case the multiplicity of elements matters.
+
+$(_DOCS_ALIASING_WARNING)
 """
 function symdiff!(s::AbstractSet, itrs...)
     for x in itrs

base/accumulate.jl

@@ -42,6 +42,8 @@ end
     cumsum!(B, A; dims::Integer)
 
 Cumulative sum of `A` along the dimension `dims`, storing the result in `B`. See also [`cumsum`](@ref).
+
+$(_DOCS_ALIASING_WARNING)
 """
 cumsum!(B::AbstractArray{T}, A; dims::Integer) where {T} =
     accumulate!(add_sum, B, A, dims=dims)
@@ -150,6 +152,8 @@ cumsum(itr) = accumulate(add_sum, itr)
 
 Cumulative product of `A` along the dimension `dims`, storing the result in `B`.
 See also [`cumprod`](@ref).
+
+$(_DOCS_ALIASING_WARNING)
 """
 cumprod!(B::AbstractArray{T}, A; dims::Integer) where {T} =
     accumulate!(mul_prod, B, A, dims=dims)
@@ -159,6 +163,8 @@ cumprod!(B::AbstractArray{T}, A; dims::Integer) where {T} =
 
 Cumulative product of a vector `x`, storing the result in `y`.
 See also [`cumprod`](@ref).
+
+$(_DOCS_ALIASING_WARNING)
 """
 cumprod!(y::AbstractVector, x::AbstractVector) = cumprod!(y, x, dims=1)
 
@@ -301,6 +307,8 @@ Cumulative operation `op` on `A` along the dimension `dims`, storing the result
 Providing `dims` is optional for vectors.  If the keyword argument `init` is given, its
 value is used to instantiate the accumulation.
 
+$(_DOCS_ALIASING_WARNING)
+
 See also [`accumulate`](@ref), [`cumsum!`](@ref), [`cumprod!`](@ref).
 
 # Examples

base/array.jl

@@ -322,6 +322,8 @@ source and `do` in the destination (1-indexed).
 The `unsafe` prefix on this function indicates that no validation is performed to ensure
 that N is inbounds on either array. Incorrect usage may corrupt or segfault your program, in
 the same manner as C.
+
+$(_DOCS_ALIASING_WARNING)
 """
 function unsafe_copyto!(dest::Array{T}, doffs, src::Array{T}, soffs, n) where T
     t1 = @_gc_preserve_begin dest
@@ -1781,6 +1783,8 @@ place of the removed items; in this case, `indices` must be a `AbstractUnitRange
 To insert `replacement` before an index `n` without removing any items, use
 `splice!(collection, n:n-1, replacement)`.
 
+$(_DOCS_ALIASING_WARNING)
+
 !!! compat "Julia 1.5"
     Prior to Julia 1.5, `indices` must always be a `UnitRange`.
 
@@ -2760,6 +2764,8 @@ Remove the items at all the indices which are not given by `inds`,
 and return the modified `a`.
 Items which are kept are shifted to fill the resulting gaps.
 
+$(_DOCS_ALIASING_WARNING)
+
 `inds` must be an iterator of sorted and unique integer indices.
 See also [`deleteat!`](@ref).
 

base/asyncevent.jl

@@ -118,22 +118,26 @@ end
 unsafe_convert(::Type{Ptr{Cvoid}}, t::Timer) = t.handle
 unsafe_convert(::Type{Ptr{Cvoid}}, async::AsyncCondition) = async.handle
 
+# if this returns true, the object has been signaled
+# if this returns false, the object is closed
 function _trywait(t::Union{Timer, AsyncCondition})
     set = t.set
     if set
         # full barrier now for AsyncCondition
         t isa Timer || Core.Intrinsics.atomic_fence(:acquire_release)
     else
-        t.isopen || return false
-        t.handle == C_NULL && return false
+        if !isopen(t)
+            close(t) # wait for the close to complete
+            return false
+        end
         iolock_begin()
         set = t.set
         if !set
             preserve_handle(t)
             lock(t.cond)
             try
                 set = t.set
-                if !set && t.isopen && t.handle != C_NULL
+                if !set && t.handle != C_NULL # wait for set or handle, but not the isopen flag
                     iolock_end()
                     set = wait(t.cond)
                     unlock(t.cond)
@@ -160,10 +164,28 @@ end
 isopen(t::Union{Timer, AsyncCondition}) = t.isopen && t.handle != C_NULL
 
 function close(t::Union{Timer, AsyncCondition})
+    t.handle == C_NULL && return # short-circuit path
     iolock_begin()
-    if isopen(t)
-        @atomic :monotonic t.isopen = false
-        ccall(:jl_close_uv, Cvoid, (Ptr{Cvoid},), t)
+    if t.handle != C_NULL
+        if t.isopen
+            @atomic :monotonic t.isopen = false
+            ccall(:jl_close_uv, Cvoid, (Ptr{Cvoid},), t)
+        end
+        # implement _trywait here without the auto-reset function, just waiting for the final close signal
+        preserve_handle(t)
+        lock(t.cond)
+        try
+            while t.handle != C_NULL
+                iolock_end()
+                wait(t.cond)
+                unlock(t.cond)
+                iolock_begin()
+                lock(t.cond)
+            end
+        finally
+            unlock(t.cond)
+            unpreserve_handle(t)
+        end
     end
     iolock_end()
     nothing
@@ -220,7 +242,10 @@ function uv_timercb(handle::Ptr{Cvoid})
         @atomic :monotonic t.set = true
         if ccall(:uv_timer_get_repeat, UInt64, (Ptr{Cvoid},), t) == 0
             # timer is stopped now
-            close(t)
+            if t.isopen
+                @atomic :monotonic t.isopen = false
+                ccall(:jl_close_uv, Cvoid, (Ptr{Cvoid},), t)
+            end
         end
         notify(t.cond, true)
     finally

base/asyncmap.jl

@@ -394,6 +394,8 @@ length(itr::AsyncGenerator) = length(itr.collector.enumerator)
 
 Like [`asyncmap`](@ref), but stores output in `results` rather than
 returning a collection.
+
+$(_DOCS_ALIASING_WARNING)
 """
 function asyncmap!(f, r, c1, c...; ntasks=0, batch_size=nothing)
     foreach(identity, AsyncCollector(f, r, c1, c...; ntasks=ntasks, batch_size=batch_size))

base/boot.jl

@@ -370,6 +370,8 @@ struct InitError <: WrappedException
     error
 end
 
+struct PrecompilableError <: Exception end
+
 String(s::String) = s  # no constructor yet
 
 const Cvoid = Nothing

base/combinatorics.jl

@@ -169,6 +169,8 @@ it is even faster to write into a pre-allocated output array with `u .= @view v[
 (Even though `permute!` overwrites `v` in-place, it internally requires some allocation
 to keep track of which elements have been moved.)
 
+$(_DOCS_ALIASING_WARNING)
+
 See also [`invpermute!`](@ref).
 
 # Examples
@@ -222,6 +224,8 @@ Note that if you have a pre-allocated output array (e.g. `u = similar(v)`),
 it is quicker to instead employ `u[p] = v`.  (`invpermute!` internally
 allocates a copy of the data.)
 
+$(_DOCS_ALIASING_WARNING)
+
 # Examples
 ```jldoctest
 julia> A = [1, 1, 3, 4];

base/env.jl

@@ -3,12 +3,29 @@
 if Sys.iswindows()
     const ERROR_ENVVAR_NOT_FOUND = UInt32(203)
 
+    const env_dict = IdDict{String, Vector{Cwchar_t}}()
+    const env_lock = ReentrantLock()
+
+    function memoized_env_lookup(str::AbstractString)
+        # Windows environment variables have a different format from Linux / MacOS, and previously
+        # incurred allocations because we had to convert a String to a Vector{Cwchar_t} each time
+        # an environment variable was looked up. This function memoizes that lookup process, storing
+        # the String => Vector{Cwchar_t} pairs in env_dict
+        var = get(env_dict, str, nothing)
+        if isnothing(var)
+            var = @lock env_lock begin
+                env_dict[str] = cwstring(str)
+            end
+        end
+        var
+    end
+
     _getenvlen(var::Vector{UInt16}) = ccall(:GetEnvironmentVariableW,stdcall,UInt32,(Ptr{UInt16},Ptr{UInt16},UInt32),var,C_NULL,0)
     _hasenv(s::Vector{UInt16}) = _getenvlen(s) != 0 || Libc.GetLastError() != ERROR_ENVVAR_NOT_FOUND
-    _hasenv(s::AbstractString) = _hasenv(cwstring(s))
+    _hasenv(s::AbstractString) = _hasenv(memoized_env_lookup(s))
 
     function access_env(onError::Function, str::AbstractString)
-        var = cwstring(str)
+        var = memoized_env_lookup(str)
         len = _getenvlen(var)
         if len == 0
             return Libc.GetLastError() != ERROR_ENVVAR_NOT_FOUND ? "" : onError(str)
@@ -21,7 +38,7 @@ if Sys.iswindows()
     end
 
     function _setenv(svar::AbstractString, sval::AbstractString, overwrite::Bool=true)
-        var = cwstring(svar)
+        var = memoized_env_lookup(svar)
         val = cwstring(sval)
         if overwrite || !_hasenv(var)
             ret = ccall(:SetEnvironmentVariableW,stdcall,Int32,(Ptr{UInt16},Ptr{UInt16}),var,val)
@@ -30,7 +47,7 @@ if Sys.iswindows()
     end
 
     function _unsetenv(svar::AbstractString)
-        var = cwstring(svar)
+        var = memoized_env_lookup(svar)
         ret = ccall(:SetEnvironmentVariableW,stdcall,Int32,(Ptr{UInt16},Ptr{UInt16}),var,C_NULL)
         windowserror(:setenv, ret == 0 && Libc.GetLastError() != ERROR_ENVVAR_NOT_FOUND)
     end

base/loading.jl

@@ -1686,7 +1686,7 @@ function include_dependency(path::AbstractString)
 end
 
 # we throw PrecompilableError when a module doesn't want to be precompiled
-struct PrecompilableError <: Exception end
+import Core: PrecompilableError
 function show(io::IO, ex::PrecompilableError)
     print(io, "Declaring __precompile__(false) is not allowed in files that are being precompiled.")
 end

base/multidimensional.jl

@@ -1179,8 +1179,7 @@ circshift!(dest::AbstractArray, src, ::Tuple{}) = copyto!(dest, src)
 Circularly shift, i.e. rotate, the data in `src`, storing the result in
 `dest`. `shifts` specifies the amount to shift in each dimension.
 
-The `dest` array must be distinct from the `src` array (they cannot
-alias each other).
+$(_DOCS_ALIASING_WARNING)
 
 See also [`circshift`](@ref).
 """
@@ -1238,6 +1237,8 @@ their indices; any offset results in a (circular) wraparound. If the
 arrays have overlapping indices, then on the domain of the overlap
 `dest` agrees with `src`.
 
+$(_DOCS_ALIASING_WARNING)
+
 See also: [`circshift`](@ref).
 
 # Examples