: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.