Add the ability to dump type information to a JSON file#16027
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straight-shoota merged 1 commit intocrystal-lang:masterfrom Jul 28, 2025
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If the environment variable
CRYSTAL_DUMP_TYPE_INFOis set, at build time the compiler will emit a bunch of type information to a JSON file at that path. The JSON looks something like:{ "types": [ { "name": "Regex", "id": 46, "min_subtype_id": 46, "supertype_id": 188, "has_inner_pointers": true, "size": 8, "align": 8, "instance_size": 56, "instance_align": 8, "instance_vars": [ { "name": "@re", "type_name": "Pointer(LibPCRE2::Code)", "offset": 8, "size": 8 }, { "name": "@jit", "type_name": "Bool", "offset": 16, "size": 1 }, { "name": "@source", "type_name": "String", "offset": 24, "size": 8 }, { "name": "@match_data", "type_name": "Crystal::ThreadLocalValue(Pointer(LibPCRE2::MatchData))", "offset": 32, "size": 16 }, { "name": "@options", "type_name": "Regex::Options", "offset": 48, "size": 8 } ] } ] }At the moment this is intended to be an internal tool that supplements the similarly named
CRYSTAL_DUMP_TYPE_IDenvironment variable. I originally made this to generate human-readable reports from GC heap dumps, but there are probably other good uses like enhancing the debugger support scripts.