Fix strings on aarch64

Should fix JuliaGraphics/QML.jl#202

Author: barche

src/CxxWrap.jl

@@ -615,8 +615,8 @@ Base.unsafe_convert(to_type::Type{<:CxxBaseRef{T}}, v::CxxBaseRef) where {T} = t
 Base.unsafe_convert(to_type::Type{<:CxxBaseRef}, v::Base.RefValue) = to_type(pointer_from_objref(v))
 
 Base.cconvert(::Type{CxxPtr{CxxPtr{CxxChar}}}, v::Vector{String}) = Base.cconvert(Ptr{Ptr{Cchar}}, v)
-Base.unsafe_convert(to_type::Type{CxxPtr{CxxPtr{CxxChar}}}, a::Base.RefArray{Ptr{Int8}, Vector{Ptr{Int8}}, Any}) = to_type(Base.unsafe_convert(Ptr{Ptr{Cchar}}, a))
-Base.unsafe_convert(to_type::Type{CxxPtr{CxxPtr{CxxChar}}}, a::Base.RefArray{Ptr{Int8}, Vector{Ptr{Int8}}, Vector{Any}}) = to_type(Base.unsafe_convert(Ptr{Ptr{Cchar}}, a))
+Base.unsafe_convert(to_type::Type{CxxPtr{CxxPtr{CxxChar}}}, a::Base.RefArray{Ptr{Cchar}, Vector{Ptr{Cchar}}, Any}) = to_type(Base.unsafe_convert(Ptr{Ptr{Cchar}}, a))
+Base.unsafe_convert(to_type::Type{CxxPtr{CxxPtr{CxxChar}}}, a::Base.RefArray{Ptr{Cchar}, Vector{Ptr{Cchar}}, Vector{Any}}) = to_type(Base.unsafe_convert(Ptr{Ptr{Cchar}}, a))
 
 cxxconvert(to_type::Type{<:CxxBaseRef{T}}, x, ::Type{IsNormalType}) where {T} = Ref{T}(convert(T,x))
 cxxconvert(to_type::Type{<:CxxBaseRef{T}}, x::Base.RefValue, ::Type{IsNormalType}) where {T} = x

src/StdLib/StdString.jl

@@ -81,9 +81,11 @@ julia> StdString(b"visible\\0hidden")
 """
 StdString(::Union{Cstring,Base.CodeUnits,Vector{UInt8},Ref{Int8},Array{Int8}})
 
-StdString(x::Cstring) = StdString(convert(Ptr{Int8}, x))
-StdString(x::Base.CodeUnits) = StdString(collect(x))
-StdString(x::Vector{UInt8}) = StdString(collect(reinterpret(Int8, x)))
+StdString(x::Cstring) = StdString(convert(Ptr{Cchar}, x))
+StdString(x::Base.CodeUnits) = StdString(collect(reinterpret(Cchar,x)))
+@static if Cchar != UInt8
+    StdString(x::Vector{UInt8}) = StdString(collect(reinterpret(Cchar, x)))
+end
 
 """
     StdString(str, n::Integer)