[m-dev.] for review: more empty array initializers

[Zoltan Somogyi]

The diff will be OK after you address Fergus's comments, but it could be
improved.

> -	list__foldl(output_number_in_vector, VarNames),
> +	( { VarNames = [] } ->
> +		io__write_string("\t0\n")
> +	;
> +		list__foldl(output_number_in_vector, VarNames)
> +	),
>  	io__write_string("};\n"),
>  	{ decl_set_insert(DeclSet0, data_addr(
>  		layout_addr(proc_layout_var_names(ProcLabel))), DeclSet) }.

If a procedure has no variable names, then it would be better not to output
a var name array at all.

> -	list__foldl(
> -		output_layout_name_in_vector("(const MR_Proc_Layout *)\n\t&"),
> -		ProcLayoutNames),
> +	( { ProcLayoutNames = [] } ->
> +		io__write_string("\tNULL\n")
> +	;
> +		list__foldl(output_layout_name_in_vector(
> +					"(const MR_Proc_Layout *)\n\t&"),
> +				ProcLayoutNames)
> +	),

At the moment, ProcLayoutNames can be the empty list only if the module does
not export any procedures or types (since types have automatically generated
unify and compare procedures). I don't think that is allowed, although I am not
sure whether the front end checks this.

> @@ -832,7 +840,11 @@
>  	io__write_string("\n"),
>  	output_layout_name_storage_type_name(VectorName, yes),
>  	io__write_string(" = {\n"),
> -	list__foldl(output_layout_name_in_vector("&"), FileLayoutNames),
> +	( { FileLayoutNames = [] } ->
> +		io__write_string("\tNULL\n")
> +	;
> +		list__foldl(output_layout_name_in_vector("&"), FileLayoutNames)
> +	),
>  	io__write_string("};\n"),
>  	{ decl_set_insert(DeclSet1, data_addr(layout_addr(VectorName)),
>  		DeclSet) }.

FileLayoutNames can be empty only if the module has *no* events with non-dummy
contexts. Even if the module has #line directives, every procedure (even
compiler-generated ones) should have a non-dummy context, so this can happen
if the module has no procedures.

> @@ -907,9 +923,13 @@
>  	io__write_string("\n"),
>  	output_layout_name_storage_type_name(LayoutName, yes),
>  	io__write_string(" = {\n"),
> -	list__foldl(
> -		output_data_addr_in_vector("(const MR_Label_Layout *)\n\t&"),
> -		LabelAddrs),
> +	( { LabelAddrs = [] } ->
> +		io__write_string("\tNULL\n")
> +	;
> +		list__foldl(output_data_addr_in_vector(
> +				"(const MR_Label_Layout *)\n\t&"),
> +			LabelAddrs)
> +	),
>  	io__write_string("};\n"),
>  	{ decl_set_insert(DeclSet0, data_addr(layout_addr(LayoutName)),
>  		DeclSet) }.

Same deal here.

Zoltan.
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