interop: keep interop traits next to the templates they specialize - #3921
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interop: keep interop traits next to the templates they specialize#3921aleksisch wants to merge 1 commit into
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A null daslang string must reach a const char * binding as "", not as nullptr. The wrap is a cast_arg<char *> / cast_arg<const char *> specialization, and it lived in ast/ast_typefactory_bind.h - a header only binding files include, 102 of them, mostly generated. That was enough while SimNode_ExtFuncCall took the function as a non type template parameter: the node was instantiated once per bound function, in the translation unit that did the binding, so the symbol had exactly one definition and every bind got the conversion its own TU compiled. Keyed on the signature alone, one node serves every bind of that signature. A game link has 27 objects defining SimNode_ExtFuncCallDirect<SimNode_ExtFuncCall<void (*)(char const*)>, void>::eval - 10 generated dasImgui TUs with the wrap, 17 engine TUs which never saw the header and instantiated the generic cast_arg instead. Same weak symbol, different bodies, so the surviving one depends on object order. ImGui::PushID then got a nullptr and crashed in ImHashStr; ld.gold --detect-odr-violations and gcc -Wodr both stay quiet about it. C++ AOT never had the hole: das_string_cast wraps every string argument of every extern, unconditionally. The interpreter is meant to match, so the specialization belongs beside the generic where no TU can miss it, not in a header that binding files opt into. Move the string casts and cast_arg<das::string> next to the generic cast_arg in simulate/interop.h, and typeFactory<ResT (*)(Args...)> next to the primary typeFactory in ast/ast_typedecl.h. That empties ast_typefactory_bind.h, so delete it, drop the include from every binding TU, and stop the C++ binder from emitting it. The remaining specializations in that family fail loudly rather than silently when unseen: cast has a declaration-only primary, typeFactory reaches ToBasicType's static_assert, and cast_arg<das::string> needs a cast<das::string> which does not exist. tests/handle_types/string_arg_never_null passes a null das string, and an empty literal, to a const char * bind in the UnitTest module. test_string_arg_length answers -1 for a nullptr, so both asserts fail with the specializations removed and pass with them in place.
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The null-string wrap (
cast_arg<char *>/cast_arg<const char *>, null ->"") lived inast/ast_typefactory_bind.h, a header only binding files include. That worked while the call node was per bound function. Now that it is per signature, one game link has 27 objects defining the same node symbol - 10 with the wrap, 17 without - so the surviving body depends on object order, andImGui::PushIDgot anullptrand crashed inImHashStr. C++ AOT never had the hole:das_string_castwraps unconditionally.Moves each trait next to the template it specializes: the
cast_argones intosimulate/interop.h,typeFactory<ResT (*)(Args...)>intoast/ast_typedecl.h. That emptiesast_typefactory_bind.h, so it is deleted, the include dropped from every binding TU, and the binder no longer emits it.tests-cpp/small/test_cast_arg_empty_stringbinds aconst char *extern the way an embedder does:-1(nullptr seen) before,0after.