Am Montag, 17. Dezember 2012, 11:47:24 schrieb Tomáš Chvátal: > 2012/12/17 Sven Eden <sven.e...@gmx.de>: > > Hello Tomáš, > > > > on my system I have set up everything with splitdebug enabled. My CFLAGS > > use - march=native, -O2 and -ggdb. > > And this is the result: (Yes, I have a dedictated partition for that.) > > > > ~ $ LC_ALL=C df -h /usr/lib/debug/. > > > > Filesystem Size Used Avail Use% Mounted on > > /dev/sda10 25G 22G 1.7G 93% /usr/lib64/debug > > > > This is a full KDE-4.9.4 system with a total > > of 1,807 packages installed. > > > > I guess the regular user would end up somewhere between your 2G and my > > 22G. > > But I bet it will be slightly more likely my end, wouldn't it? > > Well your "problem" is using -ggdb, that adds ton of stuff that makes > things large exponencialy in most cases, i bet you would be around 5-6 > on -g usage.
First, I do not want to argue. I just want to state, and prove for at least _my_ machine, that this is not true. Second, my whole system is compiled using gcc-4.7.2. This means, that the results below might differ greatly from a setting where stable gcc-4.5.4 is used for the whole. But this doesn't matter, because gcc-4.7.* will, eventually, become the stable and current gcc. (Unless it is skipped, of course.) Third, "_My_ Machine" means: My setting, hardware, USE-Flags and CFLAGS. For this the assumption -ggdb would add about 300% in size is "a bit" exsessive. Background: The option "-g" produces debugging information in the operating systems native format, already fit for GDB. -ggdb simply uses the most expressive format. Both, as I believe, result in "DWARF-2" format on my system. At least I get no difference whether I specify "-g -gdwarf-2" or "-ggdb". GDB extensions are added if possible. It seems to me, judging the results of the tests below, that those "gdb- extensions" are already enabled by default (gcc-4.7.2). I have not found any information on that regarding DWARF-2, but at least http://gcc.gnu.org/onlinedocs/gccint/DBX-Options.html states that DEFAULT_GDB_EXTENSIONS (for DBX output) is always turned on by default. Maybe that's true for DWARF-2 as well? Below are the resulting sizes of all .debug files having been generated first using "-ggdb", then using "-g" in make.conf CFLAGS. The tested packages are: 1) kde-base/kate (C++ Code, heavy library usage) and 2) dev-libs/lzo (ANSI C) I believe both are, regarding their code base, far enough apart for building up a test case. It is _not_ representative, of course. 1) --- kde-base/kate ----------------------------- Compiled with -ggdb in CFLAGS: # sum=0; for file in $(equery f kde-base/kate | grep "\.debug") ; do xSize=$(stat -c "%s" $file) ; sum=$((sum+xSize)) ; done ; echo "$sum" 32652140 Compiled with -g in CFLAGS: # sum=0; for file in $(equery f kde-base/kate | grep "\.debug") ; do xSize=$(stat -c "%s" $file) ; sum=$((sum+xSize)) ; done ; echo "$sum" 32652140 Result: No size change at all. 2) --- dev-libs/lzo ----------------------------- Compiled with -ggdb in CFLAGS: # sum=0; for file in $(equery f dev-libs/lzo | grep "\.debug") ; do xSize=$(stat -c "%s" $file) ; sum=$((sum+xSize)) ; done ; echo "$sum" 558664 Compiled with -g in CFLAGS: # sum=0; for file in $(equery f dev-libs/lzo | grep "\.debug") ; do xSize=$(stat -c "%s" $file) ; sum=$((sum+xSize)) ; done ; echo "$sum" 558304 Result: A difference of 260 bytes or 0.06%. Far away from the assumed 300%. Conclusion: I do not doubt that -ggdb adds size. It does. And maybe, if I did an emerge -e @world would reduce the size used on my system between 30% and 40%. But not about 66% like assumed. However, even if it where "around 5-6" G, it would be thrice the initial assumption of 2G. And that's the whole point. Sincerly Sven
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