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51 lines
1.9 KiB
OpenEdge ABL
51 lines
1.9 KiB
OpenEdge ABL
[NopInstruction::] The Nop Construct.
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Defining the nop construct.
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@h Definition.
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This instruction does nothing at all, has no textual representation and is
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nevertheless useful when constructing Inter in memory.
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It exists as a convenience used by Inform when it needs to write simultaneously to
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multiple positions within the same node's child list -- the idea being that
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a nop statement acts as a divider. For example, by placing the A write
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position just before a nop N, and the B write position just after, Inform
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will generate A1, A2, A3, ..., N, B1, B2, ..., rather than (say) A1, B1, A2,
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A3, B2, ... The extra N is simply ignored in code generation, so it causes
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no problems to have it.
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=
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void NopInstruction::define_construct(void) {
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inter_construct *IC = InterInstruction::create_construct(NOP_IST, I"nop");
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InterInstruction::data_extent_always(IC, 0);
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InterInstruction::allow_in_depth_range(IC, 0, INFINITELY_DEEP);
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InterInstruction::permit(IC, OUTSIDE_OF_PACKAGES_ICUP);
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InterInstruction::permit(IC, INSIDE_PLAIN_PACKAGE_ICUP);
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InterInstruction::permit(IC, INSIDE_CODE_PACKAGE_ICUP);
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METHOD_ADD(IC, CONSTRUCT_WRITE_MTID, NopInstruction::write);
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}
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@h Instructions.
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In bytecode, the frame of a |nop| instruction consists only of the two
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compulsory words -- see //Inter Nodes//.
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=
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inter_error_message *NopInstruction::new(inter_bookmark *IBM, inter_ti level,
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inter_error_location *eloc) {
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inter_tree_node *P = Inode::new_with_0_data_fields(IBM, NOP_IST,
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eloc, level);
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inter_error_message *E = VerifyingInter::instruction(InterBookmark::package(IBM), P);
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if (E) return E;
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NodePlacement::move_to_moving_bookmark(P, IBM);
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return NULL;
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}
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@h Writing to textual Inter syntax.
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The |nop| construct is not expressible in textual Inter, but can be printed out
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all the same, purely so that a stack backtrace will show it.
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=
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void NopInstruction::write(inter_construct *IC, OUTPUT_STREAM, inter_tree_node *P) {
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WRITE("nop");
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}
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