On Tue, Jul 01, 2008 at 11:37:05AM +0000, Joseph S. Myers wrote: > On Tue, 1 Jul 2008, Michael Meissner wrote: > > > On Tue, Jul 01, 2008 at 11:50:58AM +0200, Denys Vlasenko wrote: > > > On Tuesday 01 July 2008 09:24, Sajish V wrote: > > > > Thanks for the reply, Denys. > > > > My question was, why doesn't gcc catch it during compilation? It is > > > > clear > > > > that we are trying to free a variable from stack. Shouldn't gcc flag an > > > > error for this during compilation? > > > > It could. Nobody has written the code to do so, and as they say patches are > > welcome (assuming you have done the paperwork to legally contribute to GCC). > > Have you filed a feature request via bugzilla so that it can be tracked? > > An error is inappropriate; undefined behavior only occurs on execution of > the call to free, not on compilation of the program. A warning would be > fine (as would converting the call to free into an abort).
True enough from a standards point of view. Obviously having a warning would allow some invalid code to be detected at compilation time. -- Michael Meissner email: [EMAIL PROTECTED] http://www.the-meissners.org ><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>< Thanks for the reply, Denys. My question was, why doesn't gcc catch it during compilation? It is clear that we are trying to free a variable from stack. Shouldn't gcc flag an error for this during compilation? Regards, Sajish. ----- Original Message ---- From: Denys Vlasenko <[EMAIL PROTECTED]> To: [EMAIL PROTECTED] Cc: Sajish V <[EMAIL PROTECTED]> Sent: Tuesday, July 1, 2008 2:44:06 PM Subject: Re: free (static_array) On Tuesday 01 July 2008 08:38, Sajish V wrote: > Hi All, > Can you please let me know why GCC does not crib when we try to free a static > array? > main () > { > char array[100]; > free (array); > } > The above code compiles without any hitch. > Thanks, > Sajish. # ./a.out *** glibc detected *** ./a.out: free(): invalid pointer: 0xffa8b530 *** ======= Backtrace: ========= /lib/libc.so.6[0xf7ecb7a7] /lib/libc.so.6(__libc_free+0x79)[0xf7ecc0ad] ./a.out[0x804834e] /lib/libc.so.6(__libc_start_main+0x138)[0xf7e8da74] ./a.out[0x80482b5] ======= Memory map: ======== 08048000-08049000 r-xp 00000000 08:06 1315925 /.local/tmp/a.out 08049000-0804a000 rwxp 00000000 08:06 1315925 /.local/tmp/a.out 0804a000-0806b000 rwxp 0804a000 00:00 0 [heap] f7e6f000-f7e76000 r-xp 00000000 08:05 46193 /app/gcc-3.3.3/lib/libgcc_s.so.1 f7e76000-f7e77000 rwxp 00006000 08:05 46193 /app/gcc-3.3.3/lib/libgcc_s.so.1 f7e77000-f7e78000 rwxp f7e77000 00:00 0 f7e78000-f7f60000 r-xp 00000000 08:0 -- vda ><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>< Hi All, Can you please let me know why GCC does not crib when we try to free a static array? main () { char array[100]; free (array); } The above code compiles without any hitch. Thanks, Sajish. -- Summary: GCC should display a warning when trying to free a static array Product: gcc Version: unknown Status: UNCONFIRMED Severity: enhancement Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: nair dot sajish at gmail dot com http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36970
