On Wed, Feb 18, 2009 at 09:59:26AM -0800, Jonathan Adams wrote: > On Wed, Feb 18, 2009 at 11:39:02AM -0600, Nicolas Williams wrote: > > malloc()/free() from libc (or interposed via pre-loading). > > > > Rationales: > > > > [...] > > - you need to make sure no more than one allocator uses brk()/sbrk(); > > Again, this is not a problem, as long as: > > 1. neither sbrk() user assumes that consecutive calls return > consecutive addresses, > 2. no-one calls brk() to back up the break.
My statement of the brk()/sbrk() problem is certainly simplified, I agree, but it's still roughly correct because we cannot guarantee that an interposed allocator will meet (1) and (2). Without such a guarantee we must guarantee that only one allocator uses brk()/sbrk() (and that never the twain shall meet). We're not about to stop using brk()/sbrk() in our allocators, so I think this advice is correct: there can be only one allocator, either libc's or an interposed one -- anything else is a disaster waiting to happen.
