aaron.ballman added a comment. In D139010#4159307 <https://reviews.llvm.org/D139010#4159307>, @tlively wrote:
> In D139010#4158540 <https://reviews.llvm.org/D139010#4158540>, @aaron.ballman > wrote: > >> Roping in @jfb because I know he's been heavily involve in WebAssembly in >> the past and he may have ideas/opinions. >> >> High-level question: are externref, funcref, and table types all part of the >> WebAssembly standard, or are these extensions? (I wasn't aware that >> WebAssembly was a W3C standard or I'd have been asking this question much >> earlier -- sorry for that! I'm asking in regards to #4 in >> https://clang.llvm.org/get_involved.html#criteria) > > Yes, these features are all present in the WebAssembly standard: > https://www.w3.org/TR/2022/WD-wasm-core-2-20220419/syntax/types.html#table-types Thank you, that resolves any concerns I had about whether this met our usual extension criteria. I'm still uncomfortable with the type though because... it doesn't behave like anything else in the type system. I asked some questions on the test cases, and maybe knowing those answers will help me wrap my head around the design of the type. ================ Comment at: clang/test/SemaCXX/wasm-refs-and-tables.cpp:16-17 +__externref_t **t2; // expected-error {{pointer to WebAssembly reference type is not allowed}} +__externref_t ******t3; // expected-error {{pointer to WebAssembly reference type is not allowed}} +static __externref_t t4[3]; // expected-error {{only zero-length WebAssembly tables are currently supported}} +static __externref_t t5[]; // expected-error {{only zero-length WebAssembly tables are currently supported}} ---------------- This seems really... confused. We can't form a pointer to the type, but we can form an array of the type (which decays into a pointer when you sneeze near it, and it's not clear whether that should be allowed or not) so long as it's a zero-length array (which is an extension in C and C++, so do we need to silence pedantic warnings in WASM for this?). ================ Comment at: clang/test/SemaCXX/wasm-refs-and-tables.cpp:88 + varargs(1, table); // expected-error {{cannot use WebAssembly table as a function parameter}} + table == 1; // expected-error {{invalid operands to binary expression ('__attribute__((address_space(1))) __externref_t[0]' and 'int')}} + 1 >= table; // expected-error {{invalid operands to binary expression ('int' and '__attribute__((address_space(1))) __externref_t[0]')}} ---------------- ================ Comment at: clang/test/SemaCXX/wasm-refs-and-tables.cpp:95 + table ? : other_table; // expected-error {{cannot use a WebAssembly table within a branch of a conditional expression}} + (void *)table; // expected-error {{cannot cast from a WebAssembly table}} + void *u; ---------------- ================ Comment at: clang/test/SemaCXX/wasm-refs-and-tables.cpp:102 + + table[0]; + table[0] = ref; ---------------- This involves array to pointer decay, so we're forming a pointer to the table here. Why is this pointer fine but others are not? Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D139010/new/ https://reviews.llvm.org/D139010 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
