On Sun, 27 Jan 2019 at 13:56, N.M. Maclaren <n...@cam.ac.uk> wrote: > > On Jan 23 2019, Thomas König wrote: > > > >> Am 23.01.2019 um 12:36 schrieb Jonathan Wakely <jwakely....@gmail.com>: > >> > >> When there are new warnings that aren't enabled by -Wall -Wextra, > >> there's probably a reason they aren't enabled by default. > >are a higher form of life than mere Fortran > >-Wconversion-extra is an example of such a warning. > > > > It catches a very common error people make in Fortran, see > > https://gcc.gnu.org/ml/fortran/2019-01/ms are a higher form of life than > > mere sg00178.html for a false bug report which it would have caught > > early. > > > >We left it out of -Wextra because people felt it was too noisy. > > A bit like discussions on what warnings a compiler should give :-) > > There are a few points that don't seem to have been made, though I may have > missed them, which means that quite a few people would like it. > > Despite its older and wider implementation history, Fortran has never > accumulated the incompatibilities, inconsistencies and system-dependent > behaviours that C and C++ have. So the arguments against such a warning > for those don't really apply. Obviously, we wouldn't want warnings that a > construct behaved differently in Fortran 66 or in CDC or DEC Fortran, but I > don't think that there are any. > > I don't buy the claim that developer options are unsuitable for mere users. > Those of us who wrote highly portable code (and I assume that people still > do) wanted to know that a construct might misbehave on a bizarre, > unsupported but still used system, which the author had never heard of and > has no access to. While that applies to all languages, the attitude that a > portable program should work on a new system with NO modification, > pre-processing or make configuration is rare in C and C++, but still common > in Fortran. > > All experience is that warning about things that the programmer might not > have realised are potentially problematic are very useful. In the cases > where I have had to suppress warnings, most of them have been because the > warning was too crude, not that it wasn't useful. For example, in C/C++, > mixing signed and unsigned when the promoted operand was constant and not > going to change value. Or, in Fortran, converting obviously exact constants > to a higher precision - yes, even that WAS an important warning in the > 1960s, but people really should move on a bit! > > So I think that there is a strong argument for such an option in gfortran, > irrespective of whether there is for gcc and g++.
Then -Wall should enable them for Fortran.
