On Mon, Jan 30, 2012 at 9:32 AM, Jean-Daniel Dupas <[email protected]> wrote: > > Le 30 janv. 2012 à 17:37, Nico Weber a écrit : > >> Cool! >> >> One thing that this warned on in the chromium source was: >> >> ../../webkit/plugins/npapi/plugin_web_event_converter_mac.mm:213:37: >> error: format specifies type 'wchar_t *' (aka 'wchar_t *') but the >> argument has type 'const WebUChar *' (aka 'const unsigned short *') >> [-Werror,-Wformat] >> [NSString stringWithFormat:@"%S", key_event.text]); >> ~^ ~~~~~~~~~~~~~~ >> >> It looks like the current %S warning checks if the parameter type is >> wchar_t. >> http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/Strings/Articles/formatSpecifiers.html#//apple_ref/doc/uid/TP40004265 >> says that %S is always utf16 (or ucs16, it doesn't say). `man 3 >> printf` says %S is for wchar_t, but I guess it refers to the wchar_t >> type that was effective when libc / AppKit was built. On my OS X 10.6 >> box, it looks like printf expects a four byte wchar_t, while AppKit >> expects a two byte wchar_t. Since that code snippet above is about >> AppKit, the code is right and the warning is wrong (chromium isn't >> compiled with -fshort-wchar, but AppKit was, and the warning really >> needs to check against the wchar_t type that was used to build the >> library it's talking to). >> >> Since %S can expect utf32 (lib) or utf16 (AppKit), the %S warning is >> currently fairly useless. %S seems to be an Apple extension, so should >> we just hardcode %S to look for a 32bit type in c strings and for a >> 16bit type in @"" strings? >> Should we disable the warning for %S >> altogether? > > > I think we should just extends the printf checker to handle %S differently > when the format spec is 'NSString' (it already has special handling for %@).
The current %S warning implementation is wrong for just printf() as well: It compares the argument to wchar_t, but if you build your program with -fshort-wchar, clang won't warn (since your program uses wchar_t) yet printf won't work (because libc was built without -fshort-wchar). If you store your characters in an uint32* and pass that to printf() and build your program with -fshort-wchar, clang will warn (because uint32* doesn't match wchar_t* with -fshort-whar) yet the program will work correctly. _______________________________________________ cfe-commits mailing list [email protected] http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
