Jim Wilson wrote:- > Gary Funck wrote: > >While working with GCC's language hooks, we found that > >certain places in GCC test for a null value of > >lang_hooks.callgraph.expand_function, but > >cgraph_expand_function() calls the hook directly: > > When cgraph was first added, it was optional, and could be disabled if > -fno-unit-at-a-time was used, or if the language front-end did not > support cgraph. > > For a while, our intentions have been to make this mandatory, and > eliminate the -fno-unit-at-a-time option. It appears that we have > already reached the point where front end support for cgraph is > mandatory, as the code no longer works when callgraph.expand_function is > NULL. This means all of the checks for NULL are now obsolete and can be > removed. The -fno-unit-at-a-time options still exists meanwhile, but > will eventually be dropped. > > It looks like gcc-3.4 supports a NULL callgraph.expand_function hook, > and gcc-4.0 and later do not, so I'd guess this transition happened when > tree-ssa got merged in. Or maybe it was enabled by the tree-ssa work.
In general I think the idea with hooks, whether language or target, was that they were all non-NULL and so we avoided this issue and scattering conditionals everywhere. If you wanted to do nothing you used an empty hook, which was usually the default. Neil.
