Is a tab one or 7 chars when it comes to fitting on a punch card ?

[Tobias Burnus]

Hi,

Bud Davis wrote:
> fixed format source code.  
>  cat -T l.f
> !234567890123456789012345678901234567890123456789012345678901234567890123456789      
> !        1         2         3         4         5         6         7 
> ^I                                                              INTEGER A
>
> this is deceptive, because cat displayed the tab as a ^I, so the text is shown shifted right one
> position.
> g77 accepted this.  gfortran does not
> [...]
>
> is this a bug ?
>   
That is a question of view point. The Fortran 77 standard does not 
define tabs but only has spaces. With spaces there is no problem. I 
played around with some compilers and they all hand it differently 
(including whether the line is cut off after 72 characters or not). If 
you do not rely on the cut off, you can use -ffixed-line-length-none (or 
-ffixed-line-length-n with your choice of "n").

As the standard does not mandate a particular choice and the different 
compilers handle it differently, I would have the current solution; 
however, if you can give compelling reasons for another choice, we can 
change it.

> 3 baby bugs ( no XOR operator, no common block name in VOLATILE 
> statements, tab counts more than one position in fixed format).
The problem with .XOR. (see PR 33432 and 34933) is that it potentially 
conflicts with a user-defined .XOR. operator, which would reject valid 
Fortran 95 code; as written one could implement it using a flag, but as 
replacing it by .eqv. is presumably easier and makes the program more 
standard conform.

Regarding VOLATILE (PR34928): gfortran supports VOLATILE as defined by 
the Fortran 2003 standard, which does not allow "VOLATILE 
/named_common/"; as it does not conflict and is supported by many 
compilers including g77, it will probably implemented for GCC 4.4.0.

For tabs, see above.

> trust me.  this is nothing.  it has taken days after a compiler switch in the past to get the code
> to compile.  many days in some circumstances  :) 
> wonderful.  i encourage anyone who has been waiting to make the plunge to gfortran from g77 to
> give it a try.
:-)

Tobias