On Thu, Sep 12, 2002 at 03:38:32PM -0600, Jason Gunthorpe wrote:
>
> On Thu, 12 Sep 2002, Branden Robinson wrote:
>
> > Culus said "MMap *Map = 0;" was the right fix.
> >
> > It isn't.
>
> Er, doesn't all of what you've shown here prove it is the right fix
> since it isn't segfaulting?
Well, no, the behavior is still wrong in that it doesn't actually show
you any data.
> The original segfault was a simply a delete of an uninitialized pointer,
> initing it to 0 makes it safe since delete 0 is a nop.
If it's desirable for apt-cache to never return any data, then yeah,
it's valid. Otherwise it's still broken. But I think people want an
apt-cache program that isn't just a rewrite of /bin/true.
Let's see what happens when we run the same command as an ordinary user:
branden@zuul:~$ LD_LIBRARY_PATH=/tmp/branden/apt-0.5.4/build/bin gdb /tmp/branden/apt-0.5.4/build/bin/apt-cache
GNU gdb 2002-08-18-cvs
Copyright 2002 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for details.
This GDB was configured as "i386-linux"...
(gdb) set args show autoconf
(gdb) break apt-cache.cc:1362
Breakpoint 1 at 0x8052ae7: file apt-cache.cc, line 1362.
(gdb) run
Starting program: /tmp/branden/apt-0.5.4/build/bin/apt-cache show autoconf
Breakpoint 1, main (argc=3, argv=0xbffffd24) at apt-cache.cc:1362
1362 if (CmdL.DispatchArg(CmdsA,false) == false && _error->PendingError() == false)
(gdb) next
1364 MMap *Map = 0;
(gdb)
1365 if (_config->FindB("APT::Cache::Generate",true) == false)
(gdb)
1373 SrcList = new pkgSourceList;
(gdb)
1374 SrcList->ReadMainList();
(gdb)
1377 OpProgress Prog;
(gdb)
1378 pkgMakeStatusCache(*SrcList,Prog,&Map,true);
(gdb)
68 virtual ~OpProgress() {};
(gdb)
147 Rep *rep () const { return reinterpret_cast<Rep *>(dat) - 1; }
(gdb)
109 void release () { if (--ref == 0) delete this; }
(gdb)
190 { rep ()->release (); }
(gdb)
109 void release () { if (--ref == 0) delete this; }
(gdb)
428 {
(gdb)
432 if (__n > (size_t) _MAX_BYTES) {
(gdb)
347 return (((__bytes) + _ALIGN-1)/_ALIGN - 1);
(gdb)
436 __my_free_list = _S_free_list + _S_freelist_index(__n);
(gdb)
393 _Lock() { __NODE_ALLOCATOR_LOCK; }
(gdb)
442 __q -> _M_free_list_link = *__my_free_list;
(gdb)
443 *__my_free_list = __q;
(gdb)
394 ~_Lock() { __NODE_ALLOCATOR_UNLOCK; }
(gdb)
190 { rep ()->release (); }
(gdb)
109 void release () { if (--ref == 0) delete this; }
(gdb)
190 { rep ()->release (); }
(gdb)
109 void release () { if (--ref == 0) delete this; }
(gdb)
1381 if (_error->PendingError() == false)
(gdb)
1383 pkgCache Cache(Map);
(gdb)
1384 GCache = &Cache;
(gdb)
1385 if (_error->PendingError() == false)
(gdb)
85 inline bool PendingError() {return PendingFlag;};
(gdb)
1385 if (_error->PendingError() == false)
(gdb)
1386 CmdL.DispatchArg(CmdsB);
(gdb)
Package: autoconf
Priority: optional
Section: devel
Installed-Size: 1652
Maintainer: Ben Pfaff <pfaffben@debian.org>
Architecture: all
Version: 2.53-5
Replaces: autoconf (<< 2.53)
Depends: perl (>> 5.005), m4, debianutils (>= 1.8)
Recommends: automake
Suggests: gnu-standards
Conflicts: autoconf2.13 (<< 2.13-41), gettext (<< 0.10.39)
Filename: pool/main/a/autoconf/autoconf_2.53-5_all.deb
Size: 699908
MD5sum: e41215d56c83ac45c13ca73a3316ebc2
Description: automatic configure script builder
The standard for FSF source packages. This is only useful if you
write your own programs or if you extensively modify other people's
programs.
.
This version of autoconf contains many changes from the previous
release, version 2.13. If you need support for Autoconf 2.13,
you must install the autoconf2.13 package as well.
Task: c-dev
Package: autoconf
Priority: optional
Section: devel
Installed-Size: 1652
Maintainer: Ben Pfaff <pfaffben@debian.org>
Architecture: all
Version: 2.53-2
Replaces: autoconf (<< 2.53)
Depends: perl (>> 5.005), m4, debianutils (>= 1.8), autoconf2.13 (>= 2.13-41)
Recommends: automake
Suggests: gnu-standards
Conflicts: autoconf2.13 (<< 2.13-41), gettext (<< 0.10.39)
Filename: pool/main/a/autoconf/autoconf_2.53-2_all.deb
Size: 699766
MD5sum: 3ab2e6de5369984c9151776f791c4c81
Description: automatic configure script builder
The standard for FSF source packages. This is only useful if you
write your own programs or if you extensively modify other people's
programs.
.
This version of autoconf contains many changes from the previous
release, version 2.13. For now, it depends on autoconf2.13 to
provide compatibility. This will eventually go away, so please
upgrade your autoconfiscations.
Task: c-dev
137 virtual ~pkgCache() {};
(gdb)
147 Rep *rep () const { return reinterpret_cast<Rep *>(dat) - 1; }
(gdb)
109 void release () { if (--ref == 0) delete this; }
(gdb)
1388 if (Map)
(gdb)
1389 delete Map;
(gdb)
1396 if (_error->empty() == false)
(gdb)
1403 return 0;
(gdb)
0x08053505 1404 }
(gdb)
0x401850bf in __libc_start_main () from /lib/libc.so.6
(gdb)
Single stepping until exit from function __libc_start_main,
which has no line number information.
Program exited normally.
(gdb)
--
G. Branden Robinson | Intellectual property is neither
Debian GNU/Linux | intellectual nor property.
branden@debian.org | Discuss.
http://people.debian.org/~branden/ | -- Linda Richman
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