Gawk-Error: String variable interpreted as List?

[Stephan Kuhagen]

Hello

I have a problem with an old gawk-script. I did not write that script and I
do not completely understand it, lacking good source-docs and being the
longest awk-script I've ever seen.

When running with gawk 3.1.4 (on Fedora Core 4), the script worked as
expected, but it broke after an update to gawk 3.1.5 (FC6), and I don't
know, what changed in gawk, what made the program fail now. I found a
workaround, but I prefer to understand, what the problem is. So if someone
can enlighten me, please...

Here's some code:
-----
function AddFiles (path, files, input, vars,          findRoot, matchPos,
findCmd, pos, inPath, out)
{
 matchPos = length(input)+2;
...
-----

The function gets lines with path/files (output from a former find-command).
matchPos is then used for some string manipulation, and did correctly
calculated to be the length of the contents of 'input'+2. But in the newer
version this failed.

I could not see the error for some time, until I tested the following:

-----
  print "  input=" input;
  print "  substr(input, 1)=" substr(input, 1);
  matchPos = length(input)+2;
  print "StringLength1(" input ")=" length(input) " -> +2=" \
    length(tolower(input))+2;
  print "StringLength2(" input ")=" length(tolower(input)) " -> +2=" \
    length(tolower(input))+2;
-----

and the output is:

-----
  input=/home/ilab/ThirdParty
  substr(input, 1)=$INPUT /home/ilab/Thi
StringLength1(/home/ilab/ThirdParty)=28 -> +2=30
StringLength2(/home/ilab/ThirdParty)=21 -> +2=23
-----

This shows, if $input is printed with print(), it seems to have other
contents as what is seen by substr() and obviously by length(). But using
tolower() to input first, it "casts" the value of input, to what is
expected.

I'm not sure, what happens here. It seems, that input has two different
types of contents (list and string, or list and list[1]), depending on how
it is looked at.

Does anyone know what is the reason for that? Or how I can find it out?

Thanks and regards
Stephan