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Re: -Wconversion versus libstdc++


On 14/01/07, Gerald Pfeifer <gerald@pfeifer.com> wrote:
I noticed that -Wconversion now issues warnings in libstdc++.

The purpose of Wconversion has changed. You can know more about it here:


http://gcc.gnu.org/wiki/NewWconversion

For now I have opened two bug reports, and I plan to continue testing and
file further bug reports once these have been fixed but I wonder if anyone
plans to do a more systemastic set of checks?

  libstdc++/30463 [regression] -Wconversion triggers warnings for vector<>::push_back()
  libstdc++/30464 [regression] -Wconversion triggers warnings for deque<>::push_back()

Thanks, please do it, and add me (manu@gcc.gnu.org) to the CC list. Wconversion is new in GCC 4.3 and it hasn't been fully merge yet. Patches pending review are:

http://gcc.gnu.org/ml/gcc-patches/2006-12/msg00799.html
http://gcc.gnu.org/ml/gcc-patches/2006-11/msg01508.html

So testing and fine-tuning is needed (even more, since this is my
first GCC project ever).

Technically, libstdc++ did not regress.  However, from a user perspective
this really are regressions, not the least as we make break -Werror builds
due to these issues in our own libraries.

I was afraid something like that was going to happen. People have been using (the old) Wconversion without really bothering to read the manual. Even worse, they found quite interesting its undocumented warnings, so they recommended using it. Initially I proposed using a new name (Wcoercion) and keep the old Wconversion as it was. However, it was decided to rename the old Wconversion to Wconversion-traditional and put the new functionality in Wconversion.

(There is no info yet on GCC 4.3 changes because there are patches
pending review, I have a patch ready to document the changes that
depends on which changes are finally implemented).

There may be similar issues with some of the other warnings added or
improved recently.

Wextra is being modified at the moment, so watch also for that.


Cheers,

Manuel.


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