On Thu, Dec 08, 2022 at 03:28:13PM +0100, Jakub Jelinek wrote: > On Thu, Dec 08, 2022 at 09:11:54AM -0500, Marek Polacek via Gcc-patches wrote: > > On Thu, Dec 08, 2022 at 08:25:26AM +0100, Florian Weimer wrote: > > > * Marek Polacek via Gcc-patches: > > > > > > > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi > > > > index 726392409b6..2de14466dd3 100644 > > > > --- a/gcc/doc/invoke.texi > > > > +++ b/gcc/doc/invoke.texi > > > > @@ -16510,6 +16510,14 @@ The option cannot be combined with > > > > @option{-fsanitize=thread} or > > > > @option{-fsanitize=hwaddress}. Note that the only target > > > > @option{-fsanitize=hwaddress} is currently supported on is AArch64. > > > > > > > > +To get more accurate stack traces, it is possible to use options such > > > > as > > > > +@option{-O} (which, for instance, prevents most function inlining), > > > > +@option{-fno-optimize-sibling-calls} (which prevents optimizing sibling > > > > +and tail recursive calls), or @option{-fno-ipa-icf} (which disables > > > > Identical > > > > +Code Folding for functions and read-only variables). Since multiple > > > > runs > > > > +of the program may yield backtraces with different addresses due to > > > > ASLR, > > > > +it may be desirable to turn off ASLR: @samp{setarch `uname -m` -R > > > > ./prog}. > > > > > > What about -fasynchronous-unwind-tables? It should help if ASAN ever > > > reports stray segmentation faults. Whether it also helps in general > > > depends on whether ASAN maintains ABI around its instrumentation. > > > > I'm not sure. Someone else will have to decide if we want to mention > > that option as well. > > -fasynchronous-unwind-tables is on by default on many targets, so I wouldn't > mention it: > grep asynchronous_unwind_tables common/*/*/* config/*/* > common/config/aarch64/aarch64-common.cc: { OPT_LEVELS_ALL, > OPT_fasynchronous_unwind_tables, NULL, 1 }, > common/config/i386/i386-common.cc: opts->x_flag_asynchronous_unwind_tables = > 2; > common/config/loongarch/loongarch-common.cc: { OPT_LEVELS_ALL, > OPT_fasynchronous_unwind_tables, NULL, 1 }, > common/config/rs6000/rs6000-common.cc: > opts->x_flag_asynchronous_unwind_tables = 1; > common/config/s390/s390-common.cc: opts->x_flag_asynchronous_unwind_tables = > 1; > config/i386/i386-options.cc: if (opts->x_flag_asynchronous_unwind_tables > == 2) > config/i386/i386-options.cc: opts->x_flag_asynchronous_unwind_tables = > !USE_IX86_FRAME_POINTER; > config/mips/mips.cc: && > !global_options_set.x_flag_asynchronous_unwind_tables) > config/mips/mips.cc: flag_asynchronous_unwind_tables = 1; > config/rs6000/rs6000.cc: && !OPTION_SET_P > (flag_asynchronous_unwind_tables)) > config/rs6000/rs6000.cc: flag_asynchronous_unwind_tables = 1; > > On the other side, the @samp{setarch `uname -m` -R ./prog} suggestion is > very Linux specific, so if we mention it at all, it should mention that > "e.g. on Linux through ..." or something similar. > I also wouldn't mention the "and read-only variables" part, that is > irrelevant for stack traces.
Thanks, updated patch here. I've also expanded the ASLR acronym. Ok? -- >8 -- I got a complaint that while Clang docs suggest options that improve the quality of the backtraces ASAN prints (cf. <https://clang.llvm.org/docs/AddressSanitizer.html#usage>), our docs don't say anything to that effect. This patch amends that with a new paragraph. (It deliberately doesn't mention -fno-omit-frame-pointer.) gcc/ChangeLog: * doc/invoke.texi (-fsanitize=address): Suggest options to improve stack traces. --- gcc/doc/invoke.texi | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 726392409b6..1641efecf18 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -16510,6 +16510,15 @@ The option cannot be combined with @option{-fsanitize=thread} or @option{-fsanitize=hwaddress}. Note that the only target @option{-fsanitize=hwaddress} is currently supported on is AArch64. +To get more accurate stack traces, it is possible to use options such as +@option{-O} (which, for instance, prevents most function inlining), +@option{-fno-optimize-sibling-calls} (which prevents optimizing sibling +and tail recursive calls), or @option{-fno-ipa-icf} (which disables Identical +Code Folding for functions). Since multiple runs of the program may yield +backtraces with different addresses due to ASLR (Address Space Layout +Randomization), it may be desirable to turn ASLR off. On Linux, this can be +achieved with @samp{setarch `uname -m` -R ./prog}. + @item -fsanitize=kernel-address @opindex fsanitize=kernel-address Enable AddressSanitizer for Linux kernel. base-commit: d9f9d5d30feb33c359955d7030cc6be50ef6dc0a -- 2.38.1