(address . bug-guix@gnu.org)
glibmm-2.64 has this:
------
(propagated-inputs
(modify-inputs (package-propagated-inputs glibmm)
(prepend libsigc++-2)))))
------
And, the glibmm package also propagates libsigc++.
So:
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$ guix show glibmm@2.64 | grep libsigc
dependencies: doxygen@1.9.1 glib@2.70.0 graphviz@2.49.0 libsigc++@2.9.3
+ libsigc++@3.0.6 libxslt@1.1.34 m4@1.4.18 mm-common@1.0.3 perl@5.34.0
------
It propagates both versions of libsigc++, and thus cannot be installed
into a profile. 1785 packages depend on glibmm-2.64.
This breaks synfig, which propagates glibmm, as requested in its 'synfig.pc'
pkg-config file.