Re: [bug-gawk] gawk 5.0.1 patch to allow *valid* awk variable names to be assigned to SYMTAB

[pjfarley3]

Hi Arnold,

In further testing of my patch to interpret.h, I have found that there is at
least one issue no doubt due to my ignorance of the correct structure and
linking of Node * structures.

In short, assigning a number of dynamic field names (e.g., field values
input from a file using $1, $2, etc.) into SYMTAB seems to leave all of
those newly-created variables pointing to the value of the last one entered
into SYMTAB.

I have not yet nailed down why that happens, but as I said I suspect it is
my ignorance of the proper chaining and adjustment of the Node * structures
that is at fault.

Is there any internal developer design documentation on the actual structure
of the SYMTAB Node * structures other than the source code itself?  A visual
chart of any kind (ASCII art, Visio or any open source equivalent like
LibreOffice Draw or Pencil, etc.) would be a great help.

In particular, for the interpret.h operations Op_subscript_lhs and
Op_stor_sub, what value is the "lhs" Node * value pointing at after the
assignment "lhs = assoc_lookup(t1, t2);"?

I apologize for my ignorance about these internal structural issues.  I am
only trying to get to the place where I can safely assign dynamically
created variable names and then later use their dynamically assigned values,
as in for example:

FNR == 1 { for (I = 1; I <= NF; i++) { SYMTAB[$i] = computed_value } } #
Where $i has been previously verified as a valid gawk variable name value,
or suitably adjusted to be one

Where for instance $4 == "MyVar", and then later in the program I can use
code like:

If ((MyVar > x) && (MyVar < y)) { do-something }

-- or --

MyVar ~ /Some-valid-RE/ { do-something }

I admit that this is a limited use case, but it would be a significant help
in my personal projects (not intended for general distribution anywhere).

Peter

P.S. -- If I can gain an acceptable level of understanding of the Node *
structures and linking and no current visual representation is available, I
would be willing to create such a visual representation for the project to
use.

> -----Original Message-----
> From: address@hidden <address@hidden>
> Sent: Tuesday, October 8, 2019 9:10 PM
> To: 'address@hidden' <address@hidden>
> Cc: 'address@hidden' <address@hidden>
> Subject: RE: [bug-gawk] gawk 5.0.1 patch to allow *valid* awk variable
names
> to be assigned to SYMTAB
> 
> Hi Arnold,
> 
> You are welcome.  I do understand about paperwork issues, if needed I will
> supply anything required.
> 
> Let me know when you find the round tuits to look over the patch.  I know
all
> too well how scarce those can be.
> 
> Regards,
> 
> Peter
> 
> > -----Original Message-----
> > From: address@hidden <address@hidden>
> > Sent: Tuesday, October 8, 2019 3:25 AM
> > To: address@hidden
> > Cc: address@hidden
> > Subject: Re: [bug-gawk] gawk 5.0.1 patch to allow *valid* awk variable
> > names to be assigned to SYMTAB
> >
> > Hi.
> >
> > Thanks for this. I'll review the patch.
> >
> > > I assign any rights I may have in the patch code to GNU.
> >
> > Unfortunately, a simple statement such as this in an email just
> > doesn't work.  If I decide to use the patch, and that the patch needs
> > paperwork (it might be small enough to not require it) then you'll
> > have to do a formal assignment of copyright to the FSF.  (It's their
> > code, I have to play by their rules.)
> >
> > This process is relatively painless, although often a bit tedious.
> >
> > I am busy for the next while, but I'll eventually give this some
> > attention and get back to you.
> >
> > In all cases, *thank you* for wanting to contribute.
> >
> > Arnold