stack overflow bug in ofstream::operator<<
Tue Jun 28 15:56:00 GMT 2005
On Jun 28 16:42, Dave Korn wrote:
> ... perhaps only if the size is above a reasonable limit (for stack-based
> objects, probably somewhere in the range 16kB and 256kB would be a suitable
> dividing line), otherwise keep the alloca; that way, most cases will retain
> the current efficiency, and software that wants to write 2Mb strings
> probably isn't in the middle of a time-critical loop anyway!
> #define STACK_MAX_OBJECT_SIZE 65536
> char *const buf = (char *) (tot > STACK_MAX_OBJECT_SIZE) ? malloc (tot) :
> alloca (tot);
> .... snip ....
> int rv = write (buf, tot);
> if (tot > STACK_MAX_OBJECT_SIZE)
> free (buf);
> return rv;
I had something like that as a local patch but that's a bit dangerous.
Imagine a process using lots of stack space before calling writev and
there's only, say, 32K left. It would potentially get a SEGV since
alloca is used while it would still work when using malloc. Of course
malloc could fail for a process using lots of malloc'ed space. However,
malloc should at least not SEGV but just return with a NULL pointer...
So, I guess I'll just check it in using malloc.
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Project Co-Leader mailto:firstname.lastname@example.org
Red Hat, Inc.
More information about the Cygwin-developers