Hi! I have rebuilt a few packages:
https://salsa.debian.org/debian/doxygen/-/wikis/ratt_doxygen_1.12.0+ds-1-partial
with the upcoming doxygen 1.12.0+ds-1 I am preparing here:
https://salsa.debian.org/debian/doxygen/-/wikis/home

Of 572 tested packages, only 3 seem to fail the build due to doxygen,
and one of those is this one.

The failure seem to happen here:


[132]
Underfull \hbox (badness 10000) detected at line 193
[][][]

Underfull \hbox (badness 10000) detected at line 198
[][][]

Underfull \hbox (badness 10000) detected at line 201
[][][]

Underfull \hbox (badness 10000) detected at line 204
[][][]
) (./classXCSP3Core_1_1XCSP3CoreParser.tex
<./classXCSP3Core_1_1XCSP3CoreParser
__coll__graph.pdf>) (./classXCSP3Core_1_1XMLParser.tex
[133]) (./classXCSP3Core_1_1XParameterVariable.tex)
[134] (./refman.ind

[135]

[136]

[137]

[138]

[139]
Underfull \hbox (badness 791) in paragraph at lines 671--673
[]\T1/phv/m/n/10 Weighted Con-straint Sat-is-fac-tion Prob-lem file for-mat


[140]) (./refman.aux) )
(see the transcript file for additional
information)</usr/share/texlive/texmf-d
ist/fonts/type1/public/amsfonts/cm/cmex10.pfb></usr/share/texlive/texmf-dist/fo
nts/type1/public/amsfonts/cm/cmmi10.pfb></usr/share/texlive/texmf-dist/fonts/ty
pe1/public/amsfonts/cm/cmmi7.pfb></usr/share/texlive/texmf-dist/fonts/type1/pub
lic/amsfonts/cm/cmmi8.pfb></usr/share/texlive/texmf-dist/fonts/type1/public/ams
fonts/cm/cmmi9.pfb></usr/share/texlive/texmf-dist/fonts/type1/public/amsfonts/c
m/cmr10.pfb></usr/share/texlive/texmf-dist/fonts/type1/public/amsfonts/cm/cmr7.
pfb></usr/share/texlive/texmf-dist/fonts/type1/public/amsfonts/cm/cmr9.pfb></us
r/share/texlive/texmf-dist/fonts/type1/public/amsfonts/cm/cmsy10.pfb></usr/shar
e/texlive/texmf-dist/fonts/type1/public/amsfonts/cm/cmsy7.pfb></usr/share/texli
ve/texmf-dist/fonts/type1/public/amsfonts/cm/cmsy8.pfb></usr/share/texlive/texm
f-dist/fonts/type1/public/amsfonts/cm/cmsy9.pfb></usr/share/texlive/texmf-dist/
fonts/type1/urw/courier/ucrb8a.pfb></usr/share/texlive/texmf-dist/fonts/type1/u
rw/courier/ucrr8a.pfb></usr/share/texlive/texmf-dist/fonts/type1/urw/courier/uc
rro8a.pfb></usr/share/texlive/texmf-dist/fonts/type1/urw/helvetic/uhvb8a.pfb></
usr/share/texlive/texmf-dist/fonts/type1/urw/helvetic/uhvb8ac.pfb></usr/share/t
exlive/texmf-dist/fonts/type1/urw/helvetic/uhvr8a.pfb></usr/share/texlive/texmf
-dist/fonts/type1/urw/helvetic/uhvro8a.pfb>
Output written on refman.pdf (145 pages, 990611 bytes).
Transcript written on refman.log.
make[4]: Leaving directory '/<<PKGBUILDDIR>>/obj-x86_64-linux-gnu/latex'
make[3]: Leaving directory '/<<PKGBUILDDIR>>/obj-x86_64-linux-gnu'
[ 95%] Built target doc
make[3]: Leaving directory '/<<PKGBUILDDIR>>/obj-x86_64-linux-gnu'
[ 95%] Built target tb2-objects
make[2]: Leaving directory '/<<PKGBUILDDIR>>/obj-x86_64-linux-gnu'
make[1]: *** [Makefile:169: all] Error 2
make[1]: Leaving directory '/<<PKGBUILDDIR>>/obj-x86_64-linux-gnu'
dh_auto_build: error: cd obj-x86_64-linux-gnu && make -j4
"INSTALL=install --strip-program=true" VERBOSE=1 returned exit code 2
make: *** [debian/rules:3: build] Error 255
dpkg-buildpackage: error: debian/rules build subprocess returned exit
status 2

In any case I attach the full build log.

P.S. since just a handful of packages break, I plan to upload the newer
doxygen to unstable in a couple of weeks, but we can negotiate!

I don't have a fix for this bug yet, but I do want to mention that the
underfull hbox messages may be a distraction in the logs; I think the error
that causes the build to fail may be this line:

  error: Could not create output directory /<<PKGBUILDDIR>>/obj-x86_64-linux-gnu/html

(ref: line 2034 of the uncompressed toulbar2_1.2.1+dfsg-0.1 build log)

Control: retitle -1 toulbar2: FTBFS with doxygen 1.12.0
Control: severity -1 minor

The version of doxygen currently in unstable is 1.9.8+ds-2, and toulbar2
builds fine with it.

Downgrading severity, please feel free to raise it again once doxygen
1.12.0 enters sid.

Thanks,
  Emanuele