Code optimization: warning for code that hangs

[Ian Lance Taylor]

"Peter A. Felvegi" <petschy@praire-chicken.com> writes:

> My question is: wouldn't it be possible to print a warning when a jmp
> to itself or trivial infinite recursion is generated? The code
> compiled fine w/ -Wall -Wextra -Werror w/ 4.6 and 4.7.

This question is not appropriate for the mailing list gcc@gcc.gnu.org,
which is for discussions about the development of GCC.  It would be
appropriate for gcc-help@gcc.gnu.org.  Please take any followups to
gcc-help.  Thanks.

I'm not yet convinced that a -Wall warning would be worth the effort in
this case.  You have basically come up with a complicated way to write

void f() { f(); }

I suppose I think it would be reasonable to issue a -Wall warning for
code like that.  The trick is detecting it.  Obviously there is nothing
wrong with a recursive call.  What is different here is that the
recursive call is unconditional.  I don't see a way to detect that
without writing a specific warning pass to look for that case.  And I
think this case is rare enough, and easy enough to discover in other
ways, that I don't think a warning would be worth the cost in
compilation time and compiler maintenance.

If the problem can be detected cheaply in the course of an existing
pass, I would support a warning.

Ian