Fix layout flags for types that have oddly sized primitive type fields

Author: gbaraldi

src/datatype.c

@@ -577,12 +577,17 @@ void jl_compute_field_offsets(jl_datatype_t *st)
                     // Should never happen
                     throw_ovf(should_malloc, desc, st, fsz);
                 desc[i].isptr = 0;
+
                 if (jl_is_uniontype(fld)) {
                     haspadding = 1;
                     fsz += 1; // selector byte
                     zeroinit = 1;
                 }
                 else {
+                    if (fsz > jl_datatype_size(fld)) {
+                        // We have to pad the size to integer size class, but it means this has some padding
+                        haspadding = 1;
+                    }
                     uint32_t fld_npointers = ((jl_datatype_t*)fld)->layout->npointers;
                     if (((jl_datatype_t*)fld)->layout->haspadding)
                         haspadding = 1;

test/core.jl

@@ -8085,3 +8085,9 @@ let widen_diagonal(x::UnionAll) = Base.rewrap_unionall(Base.widen_diagonal(Base.
     @test Tuple === widen_diagonal(Union{Tuple{Vararg{S}}, Tuple{Vararg{T}}} where {S, T})
     @test Tuple{Vararg{Val{<:Set}}} == widen_diagonal(Tuple{Vararg{T}} where T<:Val{<:Set})
 end
+
+#58434 bitsegal comparison of oddly sized fields
+primitive type ByteString58434 (18 * 8) end
+
+@test Base.datatype_isbitsegal(Tuple{ByteString58434}) == false
+@test Base.datatype_haspadding(Tuple{ByteString58434}) == true