> On Mar 17, 2015, at 9:46 AM, David Blaikie <[email protected]> wrote: > > > > On Tue, Mar 17, 2015 at 9:42 AM, Greg Clayton <[email protected]> wrote: > > > On Mar 16, 2015, at 6:47 PM, David Blaikie <[email protected]> wrote: > > > > > > > > On Mon, Mar 16, 2015 at 5:14 PM, Adrian Prantl <[email protected]> wrote: > > > > Thanks for the explanation David, I missed that it is entirely the linker's > > (or some dwarf post-processor's) responsibility to find the module files > > and link in the debug info from the .pcm files, so debugger doesn’t notice > > a difference. > > > > I think there's still some confusion here. Sorry if I'm rehashing > > something, but I'll try to explain how this all works. > > > > Normal split DWARF: > > > > Compiler generates two files: .o and .dwo. > > .dwo has static, non-relocatable debug info. > > .o has a skeleton compile_unit that has the name of the .dwo file and a > > hash to verify that the .dwo file isn't stale when the debugger reads it. > > The .o files are all linked together, the .dwo files stay where they are. > > The debugger reads the linked executable, finds the skeleton compile_units > > contained therein, and find/loads the .dwo files > > > > The scenario I have in mind for module debug info is this: > > Module is compiled as an object file with debug info (this file is actually > > a .dwo file, even if it has some other extension - it has the > > non-relocatable debug info in it) > > .o file has a comdat'd skeleton compile_unit describing the .dwo/module file > > <from here on no extra work is required, the linker and debugger just act > > as normal> > > The .o files are linked together, the skeleton compile_units get > > deduplicated by the linker (comdat sections) > > One issue I can think of is we will need to figure out a way to make COMDAT > work with mach-o. COMDAT requires large number of sections and mach-o can > only have 255. > > Ah, fair enough - how does MachO handle inline functions (the most common use > of comdat) currently, then?
Currently mach-o relies on symbols in the symbol table being marked as weak and I believe the data for these symbols are in special sections that are marked as containing items that can be coalesced. _______________________________________________ cfe-commits mailing list [email protected] http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
