Created attachment 22438 [details]
archive containing the PDF files obtained with the chartest9 script

When an input PDF file has a character like U+2308 LEFT CEILING and has a ToUnicode CMap, the new PDF interpreter may yield an incorrect ToUnicode CMap in the generated PDF.

Here's a shell script used for some testing:

────────────────────────────────────────────────────────────────────────
#!/bin/sh

set -e

out()
{
  echo -n "$i$j ($1):"
  printf " %s" $(pdftotext chartest9$i$j$2.pdf - | tr -d '\f')
  echo
}

for i in a b
do
  for j in 0 1
  do
    cat <<'EOF' | sed "s/:$i/\\\\lceil/" | \
                  sed "s/:a//" | \
                  sed "s/J/$j/" > chartest9.tex
\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\pdfgentounicode=J
\begin{document}
\thispagestyle{empty}
$\in:a$
\end{document}
EOF

    pdflatex chartest9.tex > /dev/null
    mv chartest9.pdf chartest9$i$j.pdf
    out "pdfTeX" ""

    ps2pdf14 chartest9$i$j.pdf chartest9$i$j-new.pdf
    out "gs new" "-new"

    ps2pdf14 -dNEWPDF=false chartest9$i$j.pdf chartest9$i$j-old.pdf
    out "gs old" "-old"
  done
done
────────────────────────────────────────────────────────────────────────

I've attached an archive containing the obtained PDF files.

4 kinds of PDF inputs are tested (a0, a1, b0, b1), where
  * a: the content corresponds to "∈⌈" (ELEMENT OF + LEFT CEILING)
  * b: the content corresponds to "∈" (ELEMENT OF)
  * 0: \pdfgentounicode=0 (pdfTeX does not generate a ToUnicode CMap)
  * 1: \pdfgentounicode=1 (pdfTeX generates a ToUnicode CMap)

I've compared (see above script for details):
  * pdfTeX: PDF file generated by pdfTeX from TeX Live 2022
  * gs new: PDF file obtained with the new PDF interpreter (default)
  * gs old: PDF file obtained with the old PDF interpreter (dNEWPDF=false)

I've done the tests with the ghostscript 9.56.1~dfsg-1 Debian package.

If LEFT CEILING is not present, Ghostscript does not generate a ToUnicode CMap in all of these cases, which is fine. But if this character is present:

1. With the old PDF interpreter, Ghostscript generates a correct ToUnicode CMap.

2. With the new PDF interpreter and no input ToUnicode CMap, Ghostscript does not generate a ToUnicode CMap (the only practical issue is that one cannot get unual characters like LEFT CEILING, but this is not worse than what TeX Live 2022 can yield in any case).

3. With the new PDF interpreter and an input ToUnicode CMap like the one from TeX Live 2022, Ghostscript generates an incorrect ToUnicode CMap, which prevents one from getting usual math characters such as ELEMENT OF.

The results, where I've added ToUnicode CMap information (which I have obtained with "qpdf --stream-data=uncompress" on these PDF files):

a0 (pdfTeX): ∈d (no CMap)
a0 (gs new): ∈d (no CMap)
a0 (gs old): ∈⌈ (CMap old)
a1 (pdfTeX): ∈d (CMap 1)
a1 (gs new):    (CMap 1-new)
a1 (gs old): ∈⌈ (CMap old)
b0 (pdfTeX): ∈  (no CMap)
b0 (gs new): ∈  (no CMap)
b0 (gs old): ∈  (no CMap)
b1 (pdfTeX): ∈  (CMap 1)
b1 (gs new): ∈  (no CMap)
b1 (gs old): ∈  (no CMap)

with the following ToUnicode CMaps:

CMap old:
────────────────────────────────────────
begincmap
/CMapType 2 def
/CMapName/R11 def
1 begincodespacerange
<00><ff>
endcodespacerange
2 beginbfrange
<32><32><2208>
<64><64><2308>
endbfrange
endcmap
────────────────────────────────────────

CMap 1:
────────────────────────────────────────
begincmap
/CIDSystemInfo
<< /Registry (TeX)
/Ordering (lmsy10-lm-mathsy)
/Supplement 0
>> def
/CMapName /TeX-lmsy10-lm-mathsy-0 def
/CMapType 2 def
1 begincodespacerange
<00> <FF>
endcodespacerange
0 beginbfrange
endbfrange
0 beginbfchar
endbfchar
endcmap
────────────────────────────────────────

CMap 1-new:
────────────────────────────────────────
begincmap
/CMapType 2 def
/CMapName/R11 def
1 begincodespacerange
<00><ff>
endcodespacerange
2 beginbfrange
<32><32><00>
<64><64><00>
endbfrange
endcmap
────────────────────────────────────────