2018-06-27 23:47 GMT+02:00 Steve Kargl <s...@troutmask.apl.washington.edu>: > On Wed, Jun 27, 2018 at 10:46:05PM +0200, Janus Weil wrote: >> 2018-06-27 21:34 GMT+02:00 Thomas Koenig <tkoe...@netcologne.de>: >> > >> > And we are not going to change Fortran semantics. And I also oppose >> > defining our own subset of Fortran in the hope that people will make >> > fewer mistakes. >> > >> > A function is something that produces a value. If the value is not >> > needed to produce the correct result, the function need not be called. >> >> That's a bit oversimplified, isn't it? > > Technically, the standard says an operand need not be evaluate, > but you've asked people not to cite the Standard. I've also > pointed you to F2018 Note 10.28 where it very clearly says that > a function need not be evaluated with example nearly identical > to the one in the PR. PURE vs IMPURE (or unmarked) function > is a red herring. The standard makes no distinction.
Look, Steve. This argument has been going in circles for weeks now. I think we can stop it here. So, again: I know that the Fortran standard allows the short-circuiting of impure functions. I'm not trying to change that behavior. (I don't like it but I certainly have to accept it.) But that still leaves us with a problem: The standard allows the short-circuiting but it doesn't require it. Meaning that any other compiler that does not do it (like ifort) is not in conflict with the standard either. Many people may want to avoid such compiler-dependent behavior. That's why we need a warning. All of the discussion here has shown that using impure functions in logical expressions is not a good idea in Fortran. It is not illegal, but it should be considered bad style. That's why we need a warning: https://gcc.gnu.org/ml/fortran/2018-06/msg00160.html Does anyone agree with me that this is a useful diagnostic? Whether this warning should be included in -Wall or -Wextra or -Whereever can be debated. Is this patch ok for trunk? Cheers, Janus 2018-06-27 23:47 GMT+02:00 Steve Kargl <s...@troutmask.apl.washington.edu>: > On Wed, Jun 27, 2018 at 10:46:05PM +0200, Janus Weil wrote: >> 2018-06-27 21:34 GMT+02:00 Thomas Koenig <tkoe...@netcologne.de>: >> > >> > And we are not going to change Fortran semantics. And I also oppose >> > defining our own subset of Fortran in the hope that people will make >> > fewer mistakes. >> > >> > A function is something that produces a value. If the value is not >> > needed to produce the correct result, the function need not be called. >> >> That's a bit oversimplified, isn't it? > > Technically, the standard says an operand need not be evaluate, > but you've asked people not to cite the Standard. I've also > pointed you to F2018 Note 10.28 where it very clearly says that > a function need not be evaluated with example nearly identical > to the one in the PR. PURE vs IMPURE (or unmarked) function > is a red herring. The standard makes no distinction. > > -- > Steve
