2014-05-28 17:58 GMT-07:00 Reid Kleckner <[email protected]>: > On Wed, May 28, 2014 at 4:00 PM, Duncan P. N. Exon Smith < > [email protected]> wrote: > >> >> > On 2014-May-28, at 15:48, Reid Kleckner <[email protected]> wrote: >> > Emitting all inline functions seems like it will require semantic >> changes and it's overkill. The specific case I'm thinking of is: >> > #include <memory> >> > struct Bar; >> > struct Foo { >> > Foo(Bar *b) : p(b) {} >> > std::unique_ptr<Bar> p; >> > }; >> > >> > We need to require a complete type for Bar if we want to emit ~Foo, >> because ~unique_ptr<Bar> deletes Bar, but we don't require that currently. >> >> Hmm... nice catch. This would not be a good thing. >> > > A more accurate reduction: > > template <typename T> > struct my_unique_ptr { > my_unique_ptr(T *p) : p(p) {} > ~my_unique_ptr() { delete p; } > T *p; > }; > struct Bar; > struct Foo { > Foo(); > my_unique_ptr<Bar> p; > } >
This compiles without problems with my patch - the constructor and destructor of my_unique_ptr are never instrumented. > My original constructor would have instantiated ~unique_ptr<Bar> from the > inline ctor. > > >> > I don't know the details of coverage, but is there another way to >> represent "I saw this inline function, but nobody called it"? My straw man >> suggestion is to emit a single counter for the entry block that will either >> always be zero or be comdat merged with another TU that uses the inline >> function. >> >> That's an interesting idea, but when inline functions are used, the >> counters >> are declared `linkonce_odr` so that they'll coallesce between TUs. This >> sounds like it would violate the ODR. Something similar might work >> though. >> Hmm. > > > They should actually be weak_odr if you don't want them to be discarded. > IMO this is better than @llvm.used, which has pretty weird semantics. > > I don't know enough about what goes into the counters to figure out the > odr issue. >
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