illumos gate

ld currently allows one to do

ld -G -o libfoo.so -Flibc.so foo.o bar.o baz.o

-F means that the symbol table of our libfoo.so is used, entirely, as a filter on libc. This means that any symbol only in libfoo.so will be unusable, and any symbol in the filtee (libc) will refer to the libc symbol.

On the one hand, this is a valid, if unusual, way to build a filter library

void
printf()
{
return;
}

as a source file will cause 'printf' to be in the symbol table, filtered to libc, etc.

On the other hand, I would presume that the chances of anyone ever doing this on purpose are just about 0. We should probably emit, at least, a warning.