Messages in this thread |  | | Date | Thu, 27 Feb 2014 17:48:50 -0600 | From | Josh Cartwright <> | Subject | Re: [PATCH 1/3] typecheck: introduce assign_if() and assign_if_enabled() |
| |
On Thu, Feb 27, 2014 at 11:00:32AM -0800, Greg Kroah-Hartman wrote: > On Mon, Feb 24, 2014 at 11:08:25AM -0600, Josh Cartwright wrote: > > +/* > > + * Intended for use in static object initializers, > > + * assign_if(const_expr, function) evaluates to 'function' if 'const_expr', > > + * otherwise NULL. > > + * > > + * The type of the assign_if() expression is typeof(function), and therefore > > + * can provide typechecking regardless of 'const_expr'. > > + * > > + * gcc considers 'function' to be used and will not generate a 'defined but not > > + * used' warning when not 'const_expr', however, gcc is smart enough to > > + * eliminate 'function' if assign_if() is the only reference. > > + */ > > What version of gcc started doing this? Does llvm also do this?
I'll need to dig up some old gcc's to give this a more thorough testing; testing with clang 3.4, and it appears to have the same behavior, at least when I throw a trivial usecase at it.
$ clang --version clang version 3.4 (tags/RELEASE_34/final) Target: x86_64-unknown-linux-gnu Thread model: posix
$ cat test.c static void foo(void) { extern void BROKEN(void); BROKEN(); } void (*callback)(void) = 0 ? foo : 0;
$ clang -Wall -Werror -c test.c
$ size test.o text data bss dec hex filename 0 0 8 8 8 /tmp/test.o
$ nm test.o 0000000000000000 B callback
Although, given the feedback on the other patches, assign_if() may become just be a solution in search of a problem :).
Thanks, Josh
-- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
|  |