directories explicitly given as command-line options
each colon-delimited path in $GI_GIR_PATH (semicolon-delimited on Windows)
g_get_user_data_dir() + /gir-1.0 as per the XDG basedir spec
d + /gir-1.0 for each colon-delimited d in g_get_system_data_dirs() as per the XDG basedir spec
a path specified when GObject-Introspection was compiled, which defaults to $datadir/gir-1.0 but is something architecture-dependent like $libdir/gir-1.0 in some OS distributions
$datadir/gir-1.0
on Unix only, a hard-coded fallback to /usr/share/gir-1.0
All the tools in the GObject-Introspection ecosystem should agree on which directories to search, so I think gir-to-d should match GObject-Introspection's behaviour (although it would be fine to continue to implement the XDG basedir spec locally).
For (5), the way I would do it in C/C++ code would be to have a compile-time option that defaults to either ${datadir}/gir-1.0 or $($PKG_CONFIG --variable=girdir gobject-introspection-1.0), and then pass that into the build of the C/C++ code via -D - but I don't know the D language, so I don't know what is its equivalent, if any. Some distributions will want to override this path at build-time, so it's important for that to be possible.
If it's difficult to implement some of these search paths, then the next best thing would be for gir-to-d to implement some of them, and leave the others (for example (5)) for distributions to patch in if they find that they need to.
It looks as though cppgir searches for GIR XML (
.girfiles) in these locations (on Unix), highest-priority first:/gir-1.0for each colon-delimited d in$XDG_DATA_DIRS, with fallback as per the XDG basedir specwith some alternatives to (2) on Windows and macOS.
GObject-Introspection since 1.78.x (https://gitlab.gnome.org/GNOME/gobject-introspection/-/merge_requests/258) searches more directories than that:
$GI_GIR_PATH(semicolon-delimited on Windows)g_get_user_data_dir()+/gir-1.0as per the XDG basedir spec/gir-1.0for each colon-delimited d ing_get_system_data_dirs()as per the XDG basedir spec$datadir/gir-1.0but is something architecture-dependent like$libdir/gir-1.0in some OS distributions$datadir/gir-1.0/usr/share/gir-1.0All the tools in the GObject-Introspection ecosystem should agree on which directories to search, so I think gir-to-d should match GObject-Introspection's behaviour (although it would be fine to continue to implement the XDG basedir spec locally).
For (5), the way I would do it in C/C++ code would be to have a compile-time option that defaults to either
${datadir}/gir-1.0or$($PKG_CONFIG --variable=girdir gobject-introspection-1.0), and then pass that into the build of the C/C++ code via-D- but I don't know the D language, so I don't know what is its equivalent, if any. Some distributions will want to override this path at build-time, so it's important for that to be possible.If it's difficult to implement some of these search paths, then the next best thing would be for gir-to-d to implement some of them, and leave the others (for example (5)) for distributions to patch in if they find that they need to.
References: