test.m

#import <Cocoa/Cocoa.h>

void applicationMain()
{
	NSString *str = @"abcdefghijklmnopqrstuvwxyz";
	s
	str = [str stringByReplacingOccurrencesOfString:@"a" withString:@"b"];
	str = [str stringByReplacingOccurrencesOfString:@"b" withString:@"c"];
}

int main(int argc, char *argv[])
{
	id pool = [[NSAutoreleasePool alloc] init];
	applicationMain();
	[pool release];

	return 0;
}

test.sh

clang -cc1 -fsyntax-only -fno-caret-diagnostics -fdiagnostics-print-source-range-info -code-completion-at=test.m:6:2 test.m -x objective-c-header -fblocks -I/usr/include > out

test.vim

let out = 'out'
let file = 'test.m'

let command = 'more '.out

let time = reltime()
let clang_output = vimproc#system(command)
echo "time : " . reltimestr(reltime(time))