[PATCH] C undefined behavior fix

[Alexandre Oliva]

On Jan  5, 2002, Linus Torvalds <torvalds@transmeta.com> wrote:

> I think what people object to is optimizations that cannot be reasonably
> explained in any logical manner.

Err..  What's illogical in the following definition:

An expression such as:

  strcpy (to, "string literal" + offset)

where `"string literal" + offset' stands for an expression that can be
determined, at compile time, to be a pointer to the beginning of a
string literal not containing NULs, plus a (possibly negative) offset
that cannot be computed at compile time, is replaced with:

  memcpy (to, "string literal" + offset, sizeof "string literal" - offset)

Note: it is not necessary to verify that `offset' is in the interval
0..strlen("string literal"), because if it is not, undefined behavior
is invoked, since strcpy would dereference a pointer to memory outside
the object that was originally pointed to.

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                  aoliva@{cygnus.com, redhat.com}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist    *Please* write to mailing lists, not to me