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. 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
