зеркало из https://github.com/mozilla/gecko-dev.git
3a56bcbaeb
In the Itanium C++ ABI VTables contain extra fields before the virtual function pointer list for RTTI information, and these fields are not eliminated even when RTTI is disabled using -fno-rtti. The two relevant fields for rust-xpcom's vtables are the "offset to top" field, which contains the displacement to the top of the object from the corresponding vtable pointer as a `ptrdiff_t` (`isize`), and the "typeinfo pointer" field which points to the typeinfo object and is null when building with -fno-rtti. The VTable pointer points after these fields to the beginning of the virtual function pointer list. While these extra fields would generally not be accessed in -fno-rtti situations, gcc and clang still support `dynamic_cast<void*>` even when -fno-rtti is passed, meaning that the "offset to top" field should be present. Although I was unable to find documentation for the C++ ABI used on Darwin, it appears to behave the same as the Itanium C++ ABI when it comes to VTable layout. In order to include these fields in the manual vtables built by the rust-xpcom macros, a `&'static VTableExtra<VTableType>` is used instead of directly using the vtable type, and the vtable reference stored in the struct is offset into the allocation. As the only platform I know of to not include these extra fields is Windows, they are generated on all non-Windows platforms. Differential Revision: https://phabricator.services.mozilla.com/D115085 |
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| base | ||
| build | ||
| components | ||
| docs | ||
| ds | ||
| glue | ||
| idl-parser | ||
| io | ||
| libxpt/xptcall | ||
| reflect | ||
| rust | ||
| string | ||
| system | ||
| tests | ||
| threads | ||
| windbgdlg | ||
| xpidl | ||
| moz.build | ||
| xpcom-config.h.in | ||