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prevent stack overflows from user-defined constructor methods: strings #60876

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Merged
adienes merged 1 commit into from
Jan 30, 2026
Merged

prevent stack overflows from user-defined constructor methods: strings #60876

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6 changes: 3 additions & 3 deletions base/strings/basic.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -105,7 +105,7 @@ UInt8
See also [`ncodeunits`](@ref), [`checkbounds`](@ref).
"""
@propagate_inbounds codeunit(s::AbstractString, i::Integer) = i isa Int ?
throw(MethodError(codeunit, (s, i))) : codeunit(s, Int(i))
throw(MethodError(codeunit, (s, i))) : codeunit(s, Int(i)::Int)

"""
isvalid(s::AbstractString, i::Integer)::Bool
Expand Down Expand Up @@ -141,7 +141,7 @@ Stacktrace:
```
"""
@propagate_inbounds isvalid(s::AbstractString, i::Integer) = i isa Int ?
throw(MethodError(isvalid, (s, i))) : isvalid(s, Int(i))
throw(MethodError(isvalid, (s, i))) : isvalid(s, Int(i)::Int)

"""
iterate(s::AbstractString, i::Integer)::Union{Tuple{<:AbstractChar, Int}, Nothing}
Expand All @@ -154,7 +154,7 @@ of the iteration protocol may assume that `i` is the start of a character in `s`
See also [`getindex`](@ref), [`checkbounds`](@ref).
"""
@propagate_inbounds iterate(s::AbstractString, i::Integer) = i isa Int ?
throw(MethodError(iterate, (s, i))) : iterate(s, Int(i))
throw(MethodError(iterate, (s, i))) : iterate(s, Int(i)::Int)

## basic generic definitions ##

Expand Down
33 changes: 25 additions & 8 deletions test/faulty_constructor_method_should_not_cause_stack_overflows.jl
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
# new types with invalid constructors
for (typ, sup) in (
(:Char, :AbstractChar),
(:String, :AbstractString),
Expand All @@ -9,6 +10,18 @@ for (typ, sup) in (
@eval function Base.$typ(x::$fau) x end
end

# valid new subtype of `AbstractString`
struct MyString <: AbstractString
str::String
end
Base.lastindex(s::MyString) = lastindex(s.str)
Base.iterate(s::MyString) = iterate(s, 1)
Base.iterate(s::MyString, state) = iterate(s, Int(state)::Int)
Base.iterate(s::MyString, state::Integer) = iterate(s, Int(state)::Int)
Base.iterate(s::MyString, state::Int) = iterate(s.str, state)
Base.isequal(a::MyString, b::MyString) = isequal(a.str, b.str)
Base.:(==)(a::MyString, b::MyString) = (a.str == b.str)

using Test
using Unicode: Unicode

Expand Down Expand Up @@ -39,14 +52,18 @@ using Unicode: Unicode
end
@testset let x = FaultyInt()
@test_throws exc readbytes!(IOBuffer(), Vector{UInt8}(undef, 0), x)
@test_throws exc length("", x, x)
@test_throws exc thisind("", x)
@test_throws exc prevind("", x)
@test_throws exc prevind("", x, x)
@test_throws exc nextind("", x)
@test_throws exc nextind("", x, x)
@test_throws exc codeunit("", x)
@test_throws exc SubString("", x, x)
for s in ("", MyString(""))
@test_throws exc iterate(s, x)
@test_throws exc isvalid(s, x)
@test_throws exc length(s, x, x)
@test_throws exc thisind(s, x)
@test_throws exc prevind(s, x)
@test_throws exc prevind(s, x, x)
@test_throws exc nextind(s, x)
@test_throws exc nextind(s, x, x)
@test_throws exc codeunit(s, x)
@test_throws exc SubString(s, x, x)
end
end
@testset let x = FaultyUInt32()
@test_throws exc Char(x)
Expand Down