`-undefined dynamic_lookup` was added in #13991. `-undefined error` is the
opposite, and can be used to revert an `-undefined dynamic_lookup` flag
specified previously on the command line.
When using llvm opaque pointers, typed pointers and pointer bitcasts are
no longer needed. This also avoids needing packed struct layouts that
are nested inside pointers, letting us avoid computing struct layouts
in Sema that could cause unnecessary dependency loops.
In #1622, when targeting WebAsembly, the --allow-undefined flag
became unconditionally added to the linker.
This is not always desirable.
First, this is error prone. Code with references to unkown symbols
will link just fine, but then fail at run-time.
This behavior is inconsistent with all other targets.
For freestanding wasm applications, and applications that only use
WASI, undefined references are better reported at compile-time.
This behavior is also inconsistent with clang itself. Autoconf and
cmake scripts checking for function presence think that all tested
functions exist, but then resulting application cannot run.
For example, this is one of the reasons compilation of Ruby 3.2.0
to WASI fails with zig cc, while it works out of the box with clang.
But all applications checking for symbol existence before compilation
are affected.
This reverts the behavior to the one Zig had before #1622, and
introduces an `import_symbols` flag to ignore undefined symbols,
assuming that the webassembly runtime will define them.
* allow file level `union {}` to parse as tuple field
this was found while fuzzing zls.
* before this patch the input `union {}` crashed the parser. after
this, it parses correctly just like `struct {}`.
* adds behavior tests for both inputs `struct {}` and `union {}`,
checking that each becomes a file level tuple field.
Otherwise, we were prematurely committing `__LINKEDIT` segment LC
with outdated size (i.e., without code signature being taken into account).
This would scaffold into strict validation failures by Apple tooling.
