[Libreoffice] [PATCH] Use -gdwarf-4 by default if possible (was Re: Even more debugging info)

On Thursday 01 of December 2011, Lubos Lunak wrote:
> On Wednesday 30 of November 2011, Tom Tromey wrote:
> > These options cause debuginfo for
> > most big types to be shared across compilation units, a huge size win.
> > This also makes gdb use less memory.
>
>  I've tried it and it seems to save about 1/3 of .so size, so it indeed is
> very noticeable. Would it make sense to have this even enabled by default
> if gcc supports the option?
>
> > The downside of this feature is that not all tools have been upgraded to
> > understand it.  gdb works fine, but the 7 dwarves, and systemtap, and I
> > think valgrind, will barf.  They will all come around eventually, though
> > I am not sure when.
>
>  I have gcc-4.5.1, gdb-7.2 and valgrind 3.6.1 (openSUSE 11.4) and after
> some quick tests I didn't notice any problems with -gdwarf-4.

 As a followup, I've already noticed that gdb-7.2 has some trouble with 
completing C++ function names if the libs have been built with -gdwarf-4, but 
upgrading to gdb-7.3 fixed that, and I remember gdb used to have these kind 
of problems already somewhen without -gdwarf-4, so I don't that's such a 
serious problem. As for the rest of the tools listed above that I haven't 
tried, I think they're not used widely enough to be a blocker for this.

>  So -gdwarf-4 looks like a sensible default to me. Even if not, I'm going
> to use it (quick hack: modify your LO make script to add it to $CXXFLAGS).

 So, how about the attached patch? If it's ok, I will still wait until 3.5 has 
been branched off, just in case. I also have no idea if this should be 
enabled for the WNT_INTEL_GCC target too, but it and unxgcc were the only two 
to use -ggdbX flags.

-- 
 Lubos Lunak
 l.lunak@suse.cz

diff --git a/configure.in b/configure.in
index cafaf1f..78156c6 100644
--- a/configure.in
+++ b/configure.in
@@ -3827,6 +3827,24 @@ AC_SUBST(HAVE_GCC_VISIBILITY_FEATURE)
 AC_SUBST(HAVE_GCC_VISIBILITY_BROKEN)
 
 dnl ===================================================================
+dnl gcc DWARF-4 support (smaller debug info)
+dnl ===================================================================
+if test "$GCC" = "yes"; then
+    AC_MSG_CHECKING([whether $CC supports -gdwarf-4])
+    save_CFLAGS=$CFLAGS
+    CFLAGS="$CFLAGS -Werror -gdwarf-4"
+    AC_LINK_IFELSE([AC_LANG_PROGRAM([[]], [[ return 0; ]])],[ HAVE_GCC_DWARF_4=TRUE ],[])
+    CFLAGS=$save_CFLAGS
+    if test "$HAVE_GCC_DWARF_4" = "TRUE"; then
+        AC_MSG_RESULT([yes])
+    else
+        AC_MSG_RESULT([no])
+    fi
+fi
+
+AC_SUBST(HAVE_GCC_DWARF_4)
+
+dnl ===================================================================
 dnl allocator
 dnl ===================================================================
 AC_MSG_CHECKING([which memory allocator to use])
diff --git a/set_soenv.in b/set_soenv.in
index 4070684..6271025 100755
--- a/set_soenv.in
+++ b/set_soenv.in
@@ -1792,6 +1792,7 @@ ToFile( "HAVE_GCC_VISIBILITY_FEATURE",
                "@HAVE_GCC_VISIBILITY_FEATURE@", "e" );
 ToFile( "HAVE_GCC_VISIBILITY_BROKEN",
         "@HAVE_GCC_VISIBILITY_BROKEN@", "e" );
+ToFile( "HAVE_GCC_DWARF_4","@HAVE_GCC_DWARF_4@","e" );
 ToFile( "HAVE_LD_HASH_STYLE","@HAVE_LD_HASH_STYLE@","e" );
 ToFile( "WITH_LINKER_HASH_STYLE","@WITH_LINKER_HASH_STYLE@","e" );
 ToFile( "HAVE_LD_BSYMBOLIC_FUNCTIONS",
diff --git a/solenv/gbuild/platform/WNT_INTEL_GCC.mk b/solenv/gbuild/platform/WNT_INTEL_GCC.mk
index ae99f11..6bafd23 100644
--- a/solenv/gbuild/platform/WNT_INTEL_GCC.mk
+++ b/solenv/gbuild/platform/WNT_INTEL_GCC.mk
@@ -99,6 +99,9 @@ gb_LinkTarget_LDFLAGS += -shared-libgcc
 endif
 
 gb_DEBUG_CFLAGS := -ggdb3 -finline-limit=0 -fno-inline -fno-default-inline
+ifeq ($(HAVE_GCC_DWARF_4),TRUE)
+gb_DEBUG_CFLAGS += -gdwarf-4
+endif
 
 gb_STDLIBS := \
        mingwthrd \
@@ -162,6 +165,10 @@ gb_LinkTarget_CXXFLAGS := $(gb_CXXFLAGS) $(gb_CXXFLAGS_WERROR)
 ifeq ($(gb_SYMBOL),$(true))
 gb_LinkTarget_CXXFLAGS += -ggdb2
 gb_LinkTarget_CFLAGS += -ggdb2
+ifeq ($(HAVE_GCC_DWARF_4),TRUE)
+gb_LinkTarget_CXXFLAGS += -gdwarf-4
+gb_LinkTarget_CFLAGS += -gdwarf-4
+endif
 endif
 
 gb_LinkTarget_INCLUDE +=\
diff --git a/solenv/gbuild/platform/unxgcc.mk b/solenv/gbuild/platform/unxgcc.mk
index fe2aa7e..8bd405e7 100644
--- a/solenv/gbuild/platform/unxgcc.mk
+++ b/solenv/gbuild/platform/unxgcc.mk
@@ -164,6 +164,9 @@ gb_LINKEROPTFLAGS := -Wl,-O1
 endif
 
 gb_DEBUG_CFLAGS := -ggdb3 -finline-limit=0 -fno-inline -fno-default-inline
+ifeq ($(HAVE_GCC_DWARF_4),TRUE)
+gb_DEBUG_CFLAGS += -gdwarf-4
+endif
 
 gb_COMPILERNOOPTFLAGS := -O0
 
@@ -219,6 +222,10 @@ gb_LinkTarget_CXXFLAGS := $(gb_CXXFLAGS) $(gb_CXXFLAGS_WERROR)
 ifeq ($(gb_SYMBOL),$(true))
 gb_LinkTarget_CXXFLAGS += -ggdb2
 gb_LinkTarget_CFLAGS += -ggdb2
+ifeq ($(HAVE_GCC_DWARF_4),TRUE)
+gb_LinkTarget_CXXFLAGS += -gdwarf-4
+gb_LinkTarget_CFLAGS += -gdwarf-4
+endif
 endif
 
 # note that `cat $(extraobjectlist)` is needed to build with older gcc versions, e.g. 4.1.2 on 
SLED10