Trailing backslash in a label causes an error

[mgedmin]

Try this:

$ cat test.dot
graph {
  a[label="trailing backslash \\"];
}

$ dot -Tpng -o test.png test.dot

dot from graphiviz 2.36 on Windows complains:

Warning: c:\windows\temp\...\test.dot: syntax error in line 2 near ''

It also fails to create the PNG file.

(The actual test case I had complained about a syntax error near ',' despite there being no ',' on that line.)

dot from graphviz 2.26.3 on Ubuntu 13.10 is perfectly happy with this file and creates the expected PNG.

If the label is changed to contain anything after the escaped backslash (e.g. a single space), dot 2.36 on Windows stops complaining and starts generating PNGs.

[emdenrg]

This was due to a change in the scanner in 2.32 but I can't understand why the change was made, so I've reversed the change.

[graphviz]

On Jan 30, 2014, at 9:00 AM, Emden R. Gansner notifications@github.com wrote:

This was due to a change in the scanner in 2.32 but I can't understand why the change was made, so I've reversed the change.

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Was there any comment along with the commit?

[emdenrg]

Yes, but it more or less repeats what I said above. In the original commit, I said something about not mapping double backslashes to themselves because the latter might be escaping a quote, but that just means one needs to use an additional backslash. The muddle is partly due to the multiple layers of string quoting, once at parse time, and again when generating text output.
In any case, the current code reflects what was done in the original scanner.