On Thu, Dec 2, 2010 at 4:04 PM, Cary Coutant <ccout...@google.com> wrote: >> This isn't quite what should happen, though. If the user does not >> specify -lm on the link line, then we should not add -lm, even if LTO >> somehow introduces a function that is defined in libm. Automatically >> adding -lm would introduce a surprising dynamic dependency in some >> cases. The user should be explicit about that. > > I wouldn't expect the compiler to introduce a call to anything in libm > when -lm isn't already specified on the command line (that would break > even without LTO). > > With what I'm suggesting, we'll only resolve libcalls to libraries > that were originally specified on the command line. > >> That is, it really doesn't matter which library libcalls come from. All >> we need to know is which libraries might satisfy new libcalls. >> >> This is what leads me in the direction of copying certain libraries >> mentioned on the command line to follow the LTO objects, much as >> -pass-through does. I think we just need to make that a little bit more >> automatic. > > Another way to do this would be to put a marker in the command line > that identifies where those libraries begin, and the linker could just > go back and rescan those libraries if needed, before the final layout > of the endcaps. >
We also need to handle .a vs .so. We shouldn't add libm,so when user specifies libm.a at command line. -- H.J.
