On Tue, Dec 1, 2020 at 5:27 AM 'Fāng-ruì Sòng' via Clang Built Linux <clang-built-linux@xxxxxxxxxxxxxxxx> wrote: > > On Mon, Nov 30, 2020 at 10:05 AM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote: > > > > On Wed, Nov 4, 2020 at 9:53 AM 'Nick Desaulniers' via Clang Built > > Linux <clang-built-linux@xxxxxxxxxxxxxxxx> wrote: > > > > > > Modifies CONFIG_DEBUG_INFO_DWARF4 to be a member of a choice. Adds an > > > explicit CONFIG_DEBUG_INFO_DWARF2, which is the default. Does so in a > > > way that's forward compatible with existing configs, and makes adding > > > future versions more straightforward. > > > > > > Suggested-by: Fangrui Song <maskray@xxxxxxxxxx> > > > Suggested-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> > > > Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > > > --- > > > Makefile | 14 ++++++++------ > > > lib/Kconfig.debug | 19 +++++++++++++++---- > > > 2 files changed, 23 insertions(+), 10 deletions(-) > > > > > > diff --git a/Makefile b/Makefile > > > index 75b1a3dcbf30..e23786a4c1c7 100644 > > > --- a/Makefile > > > +++ b/Makefile > > > @@ -826,12 +826,14 @@ else > > > DEBUG_CFLAGS += -g > > > endif > > > > > > -ifndef LLVM_IAS > > > -KBUILD_AFLAGS += -Wa,-gdwarf-2 > > > -endif > > > - > > > -ifdef CONFIG_DEBUG_INFO_DWARF4 > > > -DEBUG_CFLAGS += -gdwarf-4 > > > +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF2) := 2 > > > +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4 > > > +DEBUG_CFLAGS += -gdwarf-$(dwarf-version-y) > > > +ifneq ($(dwarf-version-y)$(LLVM_IAS),21) > > > +# Binutils 2.35+ required for -gdwarf-4+ support. > > > +dwarf-aflag := $(call as-option,-Wa$(comma)-gdwarf-$(dwarf-version-y)) > > > +DEBUG_CFLAGS += $(dwarf-aflag) > > > > This changes the behavior. > > > > For the Dwarf-2 case, > > > > Previously, -gdwarf-2 was passed to $(CC), > > so the debug info was generated by gcc. > > > > Now, -Wa,-gdwarf-2 is passed to $(CC). > > -gdwarf-2 is handled by GNU as. > > So, the source info points to /tmp/<hash>.s > > instead of the original .c file. > > > > > > > > Handling the Dwarf capability is very complicated. > > > > Are you still working for v3? > > > > > > > > > +KBUILD_AFLAGS += $(dwarf-aflag) > > > endif > > > > > > ifdef CONFIG_DEBUG_INFO_REDUCED > > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > > > index 83a860126897..03c494eefabd 100644 > > > --- a/lib/Kconfig.debug > > > +++ b/lib/Kconfig.debug > > > @@ -256,14 +256,25 @@ config DEBUG_INFO_SPLIT > > > to know about the .dwo files and include them. > > > Incompatible with older versions of ccache. > > > > > > +choice > > > + prompt "DWARF version" > > > + help > > > + Which version of DWARF debug info to emit. > > > + > > > +config DEBUG_INFO_DWARF2 > > > + bool "Generate DWARF v2 debuginfo" > > > + help > > > + Generate DWARF v2 debug info. > > > + > > > config DEBUG_INFO_DWARF4 > > > bool "Generate dwarf4 debuginfo" > > > depends on $(cc-option,-gdwarf-4) > > > help > > > - Generate dwarf4 debug info. This requires recent versions > > > - of gcc and gdb. It makes the debug information larger. > > > - But it significantly improves the success of resolving > > > - variables in gdb on optimized code. > > > + Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+. > > > + It makes the debug information larger, but it significantly > > > + improves the success of resolving variables in gdb on optimized code. > > > + > > > +endchoice # "DWARF version" > > > > > > config DEBUG_INFO_BTF > > > bool "Generate BTF typeinfo" > > > -- > > > 2.29.1.341.ge80a0c044ae-goog > > > We can bump -Wa,-gdwarf-2 to -Wa,-gdwarf-3 since GNU actually emits > DWARF v3 DW_AT_ranges (see > https://sourceware.org/bugzilla/show_bug.cgi?id=26850 ) > This can avoid the `warning: DWARF2 only supports one section per > compilation unit` warning for Clang. I am not a DWARF spec expert. Please teach me. In my understanding, "DWARF2 only supports one section ..." is warned only when building .S files with LLVM_IAS=1 If this is due to the limitation of DWARF v2, why is it OK to build .c files with LLVM_IAS? > > Deleting -Wa,-gdwarf-2 also sounds good to me if people can verify > their debugging experience is not regressed (I believe it is useless). > > > -- > 宋方睿 > > -- > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/CAFP8O3Ki9HoqcV450fn29fBOWAbmuGAdB6USLz8pGsW4Vzf7sg%40mail.gmail.com. -- Best Regards Masahiro Yamada
