On Thu, Dec 2, 2010 at 10:37 AM, Ian Lance Taylor <i...@google.com> wrote: > "H.J. Lu" <hjl.to...@gmail.com> writes: > >> On Thu, Dec 2, 2010 at 9:41 AM, Ian Lance Taylor <i...@google.com> wrote: >>> "H.J. Lu" <hjl.to...@gmail.com> writes: >>> >>>> How do you deal with -lm: >>> >>> I believe we have agreed that LTO can only introduce new symbol >>> references that are satisfied by -lc and -lgcc. Under those conditions, >> >> Have you looked my testcase? The assumption of "LTO can only >> introduce new symbol references that are satisfied by -lc and -lgcc." >> is wrong. My testcase shows LTO may introduce new symbol references >> to libm. > > You're right, I didn't fully grasp that the reference to sin in the > source code was somehow being removed and then re-added. > > However, I really don't see why this is a serious flaw in my proposal. > You have shown a case in which LTO can introduce a new symbol reference > to -lm. So we just treat -lm as we do -lc and -lgcc. This is similar > to how the g++ driver already treats -lm. It's a detail, not a major > problem.
g++ adds -lm since libstdc++ uses libm. If we do it in gcc, we may add run-time dependency on libm.so to all C programs even if they don't use libm at all. > A major problem would be if LTO could introduce a new symbol reference > which required changing the way we search user defined archives. > Your proposal means we have to add lots of library references to GCC driver. I am not sure if it is a good idea. -- H.J.
