xpcom/base/MacHelpers.mm appears to ask an NSString (UTF-16) to provide a UTF-8 conversion and then immediately converts the result back to UTF-16. We should instead ask the NSString for its (UTF-16) length, resize the nsAString to that length and ask the NSString to write its contents to aCountryCode.BeginWriting(). (Not that converting a couple of characters matters much perf-wise, but I'm changing the signature of AppendUTF8toUTF16 so *some* change to these lines is going to be needed anyway.)

Trying to write a patch without a Mac...

Looks like neither bug 346345 nor bug 334670 ever got fixed. :-(

Comment on attachment 8962265 [details] Bug 1448772 - Avoid back-and-forth UTF-16 to UTF-8 to UTF-16 conversions in xpcom/base/MacHelpers.mm. https://reviewboard.mozilla.org/r/231126/#review238420 Looks good, thank you! ::: toolkit/crashreporter/mac_utils.mm:22 (Diff revision 14) > - [name getCharacters:nameBuffer]; > - [reason getCharacters:reasonBuffer]; > + (void) mozilla::CopyCocoaStringToXPCOMString(name, nameStr); > + (void) mozilla::CopyCocoaStringToXPCOMString(reason, reasonStr); You could also use mozilla::unused << here.

Pushed by hsivonen@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/24f434072ecd Avoid back-and-forth UTF-16 to UTF-8 to UTF-16 conversions in xpcom/base/MacHelpers.mm. r=mstange