https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116016
--- Comment #62 from Alejandro Colomar <alx at kernel dot org> --- (In reply to qinzhao from comment #61) > (In reply to qinzhao from comment #60) > > I came up with the following draft for the documentation of the new > > __builtin_get_counted_by, let me know your comments and suggestions: > > After discussing with Bill on the Clang side, I confirmed that Clang does > not have the same builtin __builtin_has_attributes as in GCC. So, in order > to keep the user interface consistent between these two compilers. the new > __builtin_get_counted_by is defined as following: > > Builtin-in Function: type __builtin_get_counted_by (ptr) > > The built-in function __builtin_get_counted_by checks whether the array > object pointed by the pointer PTR has another object associated with it that > represents the number of elements in the array object through counted_by > attribute (i.e, the counted-by object). If so, returns a pointer to the > corresponding counted-by object. If such counted-by object does not exist, > return a NULL pointer. What's the value of returning NULL instead of just failing the compilation with an error? I expect it will be easier to write safe code if it's impossible to misuse this API, by having a hard compiler error if it's misused. Just like ARRAY_SIZE() (and a future __lengthof__) breaks compilation if you use it on a non-array.
