[PATCH] D33899: Allow VersionPrinter to print to arbitrary raw_ostreams

[Mehdi AMINI via Phabricator via llvm-commits]

mehdi_amini added inline comments.


================
Comment at: include/llvm/Support/CommandLine.h:69
+typedef void (*VersionPrinterTy)(raw_ostream &);
+
 ///===---------------------------------------------------------------------===//
----------------
dim wrote:
> mehdi_amini wrote:
> > Using a `std::function` (or maybe `llvm::function_ref`) would be allowing for more rich object to be passed in (i.e. a client that may want state to be passed around).
> Maybe, but how would `VersionPrinter::print` or `VersionPrinter::operator=` know how to call that function object, and which parameters to pass?
> 
> In any case it looks like `llvm::function_ref` also doesn't support variable function types, you'd still need to settle on `function_ref<void(raw_ostream &)>` as 'the' type for version printing functions.  With `std::function` it seems to be the same.
> 
> The only advantage would maybe be the ownership of the function object, but I'm not sure if that is a big deal breaker in this case.  It's just for printing a version field. :)
It is not about the function signature, it is about being able to have a callback with *state*. 

i.e. what people do in C is adding a `void *` parameter to the callback signature and have the caller passing it in alongside the callback, C++ has std::function for this.



https://reviews.llvm.org/D33899