Fix 452

src/generator/codegen.jl

@@ -541,7 +541,7 @@ function emit!(dag::ExprDAG, node::ExprNode{StructMutualRef}, options::Dict; arg
             # if `leaf_ty.sym` can not be found in `tags` and `ids` then it's in `ids_extra`
             field_idx == typemax(Int) && @assert haskey(dag.ids_extra, leaf_ty.sym)
 
-            if node_idx < field_idx
+            if node_idx < field_idx && field_idx != typemax(Int)
                 # this assumes that circular references were removed at pointers
                 @assert is_jl_pointer(jlty) "Expected this field to be a pointer: $(struct_sym).$(field_sym)"
 

test/generators.jl

@@ -175,3 +175,8 @@ end
     ctx = create_context([joinpath(@__DIR__, "include/enum.h")], get_default_args(), options)
     @test_logs (:info, "Done!") match_mode = :any build!(ctx)
 end
+
+@testset "Issue 452 - StructMutualRef" begin
+    ctx = create_context([joinpath(@__DIR__, "include/struct-mutual-ref.h")], get_default_args())
+    @test_logs (:info, "Done!") match_mode = :any build!(ctx)
+end

test/include/struct-mutual-ref.h

@@ -0,0 +1,26 @@
+#include <stdlib.h>
+#include <stdbool.h>
+
+struct mutualref {
+  int type;
+
+  struct buffer *buffer;
+
+  int n_dims;
+  int64_t ne[10]; 
+  size_t nb[10]; 
+
+  int32_t op_params[10 / sizeof(int32_t)];
+
+  bool is_param;
+
+  struct mutualref *grad;
+  struct mutualref *src[10];
+
+  struct mutualref *view_src;
+  size_t view_offs;
+
+  void *data;
+
+  char padding[12];
+};