If a key is defined with no value, dequote will allocate a buffer with a
length of 0. Since the buffer's length is 0, any manipulation of its
content is UB.
Example .pc file:
prefix=/usr
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include
xcflags=
xlibs= -lSM -lICE -lX11
Name: Obt
Description: Openbox Toolkit Library
Version: 3.6
Requires: glib-2.0 libxml-2.0
Libs: -L${libdir} -lobt ${xlibs}
Cflags: -I${includedir}/openbox/3.6 ${xcflags}
Output using pkgconf 1.5.2 on x86_64 Linux/musl:
% pkgconf --cflags obt-3.5
-I/usr/include/openbox/3.6 \�\\�I\�\ -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -I/usr/include/libxml2
9b7affe0b1