[Patch, Fortran] PR32987 - Allow TAB in FORMAT statements as extension and warn with -std=f*

[Jerry DeLisle]

Tobias Burnus wrote:
> :ADDPATCH fortran:
> 
> In FORMAT statements, standard Fortran only allow tabs ('\t') in string
> literals. However, all other compiler I checked allow it: ifort, g95,
> NAG f95, sunf95, openf95. Except of ifort (with the option "-stand f95")
> none of the compilers even print a compile-time warning.
> 
> gfortran currently accepts tabs quietly at compile time, but gives a
> run-time error.
> 
> Given that all other compilers allow it, I would suggest to allow it as
> well - and follow ifort by giving a warning with -std=f95/f2003.
> (Actually, I have chosen to give a gfc_warning instead of an gfc_error
> to save myself from several levels of error propagation :-)
> 
> Note, however, that Steve disagrees (see PR for full quote):
> 
> "A tab is not a legal substitution for a space character." [...]
> "Here's a patch that permits gfortran to accept your INVALID code."
> (His patch is the same as the libgfortran part of my patch; he continues
> then:)
> "[...] I will activity oppose application of this patch by others."
> 
> Reasoning by Steve:
> 
> "gfortran has been around for a long time now and this is the first
> report of the tab-in-format runtime error. gfortran should complain
> loudly that the code is invalid."
> 
> 
> While I still think accepting it with a compile-time warning is enough,
> I strongly believe that there should be in any case a COMPILE-TIME
> diagnostic whatever we decide about accepting or rejecting it at run time.
> 
I think everyone is in agreement that a compile time diagnostic should be given:

I think the default behavior, without -std=XXX, should give the warning at compile.

I think that for -std=f95 or -std=f2003, an error should be given at compile time.

At runtime, quiet acceptance for default, there is no runtime for -std=

Regards.

Jerry