Issue 4369: silence warning in page-breaking.cc

[Dan Eble, 2015-05-04 23:49:14]

I noticed these recently and it seemed appropriate to fix them this way.

[dak, 2015-05-05 00:11:07]

https://codereview.appspot.com/231370043/diff/1/lily/beaming-pattern.cc
File lily/beaming-pattern.cc (right):

https://codereview.appspot.com/231370043/diff/1/lily/beaming-pattern.cc#newco...
lily/beaming-pattern.cc:170: int start_dur =
intlog2(static_cast<int>(infos_[i+1].start_moment_.main_part_.den()));
intlog2(0) aborts the program.  So if den is some large power of 2 that
converted into int is 0, one can trigger an abort here.

In other words: GCC might have a point here.  I don't know how likely the code
is to fall apart for other kinds of overflow though.

https://codereview.appspot.com/231370043/diff/1/lily/page-breaking.cc
File lily/page-breaking.cc (right):

https://codereview.appspot.com/231370043/diff/1/lily/page-breaking.cc#newcode...
lily/page-breaking.cc:1136: || (prev && scm_is_eq (prev->page_permission_,
ly_symbol2scm ("force"))))
Yes, this one annoyed me a few times as well but then it scrolled off and I
forgot looking after it.

Maybe we should enable compilation with warning-as-errors and switch it off for
parser.cc (since the warning in the generated code can't be avoided using
sensible means).

[Dan Eble, 2015-05-05 00:30:05]

https://codereview.appspot.com/231370043/diff/1/lily/beaming-pattern.cc
File lily/beaming-pattern.cc (right):

https://codereview.appspot.com/231370043/diff/1/lily/beaming-pattern.cc#newco...
lily/beaming-pattern.cc:170: int start_dur =
intlog2(static_cast<int>(infos_[i+1].start_moment_.main_part_.den()));
On 2015/05/05 00:11:06, dak wrote:
> intlog2(0) aborts the program.  So if den is some large power of 2 that
> converted into int is 0, one can trigger an abort here.
> 
> In other words: GCC might have a point here.  I don't know how likely the code
> is to fall apart for other kinds of overflow though.

OK, I'll revert this one and leave it for someone more familiar with the code.

[Dan Eble, 2015-05-05 01:33:16]

revert beaming-pattern.cc