Fix getfield of potentially undef inline immutable field (#37511)

The undef ref error may be thrown at the wrong time or not at all and may cause crashes.

Author: yuyichao

src/cgutils.cpp

@@ -1687,16 +1687,18 @@ static bool emit_getfield_unknownidx(jl_codectx_t &ctx,
         else if (is_tupletype_homogeneous(stt->types)) {
             assert(nfields > 0); // nf == 0 trapped by all_pointers case
             jl_value_t *jft = jl_svecref(stt->types, 0);
+            assert(jl_is_concrete_type(jft));
             idx = idx0();
             Value *ptr = maybe_decay_tracked(ctx, data_pointer(ctx, strct));
-            if (!stt->mutabl && !(maybe_null && jft == (jl_value_t*)jl_bool_type)) {
+            if (!stt->mutabl && !(maybe_null && (jft == (jl_value_t*)jl_bool_type ||
+                                                 ((jl_datatype_t*)jft)->layout->npointers))) {
                 // just compute the pointer and let user load it when necessary
                 Type *fty = julia_type_to_llvm(ctx, jft);
                 Value *addr = ctx.builder.CreateInBoundsGEP(fty, emit_bitcast(ctx, ptr, PointerType::get(fty, 0)), idx);
                 *ret = mark_julia_slot(addr, jft, NULL, strct.tbaa);
                 return true;
             }
-            *ret = typed_load(ctx, ptr, idx, jft, strct.tbaa, nullptr, false);
+            *ret = typed_load(ctx, ptr, idx, jft, strct.tbaa, nullptr, maybe_null);
             return true;
         }
         else if (strct.isboxed) {
@@ -1787,12 +1789,14 @@ static jl_cgval_t emit_getfield_knownidx(jl_codectx_t &ctx, const jl_cgval_t &st
             }
             return mark_julia_slot(addr, jfty, tindex, tbaa);
         }
-        else if (!jt->mutabl && !(maybe_null && jfty == (jl_value_t*)jl_bool_type)) {
+        assert(jl_is_concrete_type(jfty));
+        if (!jt->mutabl && !(maybe_null && (jfty == (jl_value_t*)jl_bool_type ||
+                                            ((jl_datatype_t*)jfty)->layout->npointers))) {
             // just compute the pointer and let user load it when necessary
             return mark_julia_slot(addr, jfty, NULL, tbaa);
         }
         unsigned align = jl_field_align(jt, idx);
-        return typed_load(ctx, addr, NULL, jfty, tbaa, nullptr, true, align);
+        return typed_load(ctx, addr, NULL, jfty, tbaa, nullptr, maybe_null, align);
     }
     else if (isa<UndefValue>(strct.V)) {
         return jl_cgval_t();

test/core.jl

@@ -7330,3 +7330,69 @@ function c37265_2(d)
     e
 end
 @test_throws TypeError c37265_2(0)
+
+struct PointerImmutable
+    a::Any
+    b::Int
+end
+struct NullableHomogeneousPointerImmutable
+    x1::PointerImmutable
+    x2::PointerImmutable
+    x3::PointerImmutable
+    NullableHomogeneousPointerImmutable() = new()
+    NullableHomogeneousPointerImmutable(x1) = new(x1)
+    NullableHomogeneousPointerImmutable(x1, x2) = new(x1, x2)
+    NullableHomogeneousPointerImmutable(x1, x2, x3) = new(x1, x2, x3)
+end
+
+function getfield_knownindex_unused(v)
+    v.x1
+    return
+end
+
+function getfield_unknownindex_unused(v, n)
+    getfield(v, n)
+    return
+end
+
+function getfield_knownindex_used1(r, v)
+    fld = v.x1
+    r[] += 1
+    return fld
+end
+
+function getfield_knownindex_used2(r, v)
+    fld = v.x1
+    r[] += 1
+    return fld.a
+end
+
+function getfield_knownindex_used3(r, v)
+    fld = v.x1
+    r[] += 1
+    return fld.b
+end
+
+let v = NullableHomogeneousPointerImmutable(),
+    v2 = NullableHomogeneousPointerImmutable(PointerImmutable(1, 2)),
+    r = Ref(0)
+    @test_throws UndefRefError getfield_knownindex_unused(v)
+    @test_throws UndefRefError getfield_unknownindex_unused(v, 1)
+    @test_throws UndefRefError getfield_unknownindex_unused(v, :x1)
+    @test_throws UndefRefError getfield_knownindex_used1(r, v)
+    @test r[] == 0
+    @test_throws UndefRefError getfield_knownindex_used2(r, v)
+    @test r[] == 0
+    @test_throws UndefRefError getfield_knownindex_used3(r, v)
+    @test r[] == 0
+
+    @test getfield_knownindex_unused(v2) === nothing
+    @test getfield_unknownindex_unused(v2, 1) === nothing
+    @test getfield_unknownindex_unused(v2, :x1) === nothing
+    @test getfield_knownindex_used1(r, v2) === PointerImmutable(1, 2)
+    @test r[] == 1
+    @test getfield_knownindex_used2(r, v2) === 1
+    @test r[] == 2
+    @test getfield_knownindex_used3(r, v2) === 2
+    @test r[] == 3
+end