On Tue, Nov 20, 2007 at 02:03:12PM +0800, Li Zefan wrote: >WANG Cong wrote: >> On Mon, Nov 19, 2007 at 09:10:44PM -0800, H. Peter Anvin wrote: >>> WANG Cong wrote: >>>> On Tue, Nov 20, 2007 at 10:13:42AM +0800, zhengyi wrote: >>>>> Is there any relevance to the kernel ? >>>>> >>>>> I found the folowing code here: >>>>> http://linux.solidot.org/article.pl?sid=07/11/19/0512218&from=rss >>>>> >>>>> ------------------------------------------------------------------- >>>>> int main( void ) >>>>> { >>>>> int i=2; >>>>> if( -10*abs (i-1) == 10*abs(i-1) ) >>>>> printf ("OMG,-10==10 in linux!\n"); >>>>> else >>>>> printf ("nothing special here\n") ; >>>>> >>>>> return 0 ; >>>>> } >>>> I think no. It is considered a bug in abs(), kernel, of course, >>>> doesn't use glibc's abs(). >>>> >>> Wrong. >>> >>> abs() is internal to gcc, and the above is optimized out at compile >>> time, so any user of abs() as a function at all is vulnerable. >> >> This is an urgent bug, I think. >> >> And you mean abs() is not in glibc, then where is it? Built in gcc? >> And what's more, why not put it in glibc? >> > >Gcc optimises abs() to use gcc builtin-in abs(). So if we use -fno-builin, >we'll get the correct result. That is to say the bug has nothing to do with >glibc. > >And this bug has been fixed just several days ago. > >http://www.nabble.com/-PATCH--Fix-PR34130,-extract_muldiv-broken-t4826688.html >
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