[Bug libstdc++/30464] [regression] -Wconversion triggers warnings for deque<>::push_back()

[manu at gcc dot gnu dot org]

------- Comment #16 from manu at gcc dot gnu dot org  2007-01-28 19:47 -------
(In reply to comment #15)
> FYI: I'm right now auditing the code for conversions larger -> smaller integer
> type and immediately adjusting it in the process. Only very few so far. To be
> clear, I'm punting on conversions between same size types which, apparently,
> people don't believe should be flagged as part of -Wconversion, maybe not at
> all.

I think that we agreed that people using -Wconversion do want warnings for
larger->smaller conversions. When you mention same size types, do you mean
conversions between signed and unsigned types? or am I missing something here?
(we also warn for conversions between integer and floating-point types, no
matter what size they are).

Nevertheless, I am interested in how many (large signed) -> (small unsigned)
you have found, since it is not clear to me whether those should be warned by
-Wconversion or should be considered a signedness conversion. For example:

void f (char *p1, char *p2)
{
  unsigned short us = p1 - p2;
}

Gabriel, what do you think about this case?

I am also interested in how many (negative constant)->unsigned conversions you
have found, because I would like to keep those in Wconversion as they have
always been. 

Thanks.

Manuel.

PS: Also, currently Wconversion in C++ is not complete: there are some (many?)
situations that we want to warn but we don't do it yet. In particular, any
conversion that uses convert_like_real (which I think that is used quite often)
and implicit conversions of the operands of binary operations. I am waiting for
this patch http://gcc.gnu.org/ml/gcc-patches/2006-12/msg00799.html
to be reviewed. So, I am afraid that you may get more warnings once that patch
gets committed.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30464