phil-blain created this revision. phil-blain added reviewers: echristo, dblaikie. Herald added subscribers: dexonsmith, inglorion. Herald added a reviewer: JDevlieghere. Herald added a project: clang.
If `-Wl,object_path_lto,<lto-filename>.o` is not passed at link time when compiling and linking in separate steps with `-flto` and `-g`, the temporary file used for Link Time Optimization is deleted by the linker, so the executable is missing debug symbols and can't be easily debugged, and `dsymutil` can't be run. Document this behaviour. Repository: rG LLVM Github Monorepo https://reviews.llvm.org/D82733 Files: clang/docs/CommandGuide/clang.rst Index: clang/docs/CommandGuide/clang.rst =================================================================== --- clang/docs/CommandGuide/clang.rst +++ clang/docs/CommandGuide/clang.rst @@ -474,6 +474,14 @@ optimization. With "thin", :doc:`ThinLTO <../ThinLTO>` compilation is invoked instead. + Note: on Darwin, when using :option:`-flto` along with :option:`-g` and + compiling and linking in separate steps, you also need to pass + `-Wl,object_path_lto,<lto-filename>.o` at the linking step to instruct the + ld64 linker not to delete the temporary object file generated during Link + Time Optimization (this flag is automatically passed to the linker by Clang + if compilation and linking are done in a single step). This allows debugging + the executable as well as generating the `.dSYM` bundle using :manpage:`dsymutil(1)`. + Driver Options ~~~~~~~~~~~~~~
Index: clang/docs/CommandGuide/clang.rst =================================================================== --- clang/docs/CommandGuide/clang.rst +++ clang/docs/CommandGuide/clang.rst @@ -474,6 +474,14 @@ optimization. With "thin", :doc:`ThinLTO <../ThinLTO>` compilation is invoked instead. + Note: on Darwin, when using :option:`-flto` along with :option:`-g` and + compiling and linking in separate steps, you also need to pass + `-Wl,object_path_lto,<lto-filename>.o` at the linking step to instruct the + ld64 linker not to delete the temporary object file generated during Link + Time Optimization (this flag is automatically passed to the linker by Clang + if compilation and linking are done in a single step). This allows debugging + the executable as well as generating the `.dSYM` bundle using :manpage:`dsymutil(1)`. + Driver Options ~~~~~~~~~~~~~~
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