While the fixxref valid link check is good at catching typos it also throws a lot of invalid warnings. We don't have a way to suppress them right now.

The reason is that gtk-doc opimistically creates links for function(), @CONSTANT, %parameter, #Object. Especially function() can also happen when someone e.g. writes "see posix_memalign()" or in code examples "foo()". Other links get created by gtkdoc for the parameter and return type table below functions/structs etc.

One strategy here could be to mark these implicit links to not warn. We can assume that the types are not misspelled as those would be caught by the compiler.

For explicit links we could use a supression file. The file could be:
# comment
posix_memalign man://posix_memalign
foo

The posix_memalign would tell gtkdoc how to link to it properly. the foo entry would cause gtkdoc to suppress the warning.

A different approach would be to e.g. have a tags for e.g. /usr/inlcude file and suppress warnings for valid symbols.

We could also consider to e.g. suppress warnings for entries in: nm -g --undefined-only $(builddir)/*.o