On Thu, Dec 08, 2022 at 04:00:15PM +0100, Jakub Jelinek wrote: > On Thu, Dec 08, 2022 at 09:34:34AM -0500, Marek Polacek wrote: > > 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), > > Still not sure about this part. For one, I wonder if we shouldn't > recommend -O0, -O1 or -Og instead of just one of them, and I'm also not sure > how much function inlining is prevented with -O1.
Right, that's why I put "most" in there. But I think we should mention -O0 and -Og as well. > always_inline functions are certainly inlined even at -O0 or -Og (at least > when called directly), -O1 adds > { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_finline_functions_called_once, NULL, 1 > }, > to that, -O2 adds > { OPT_LEVELS_2_PLUS, OPT_findirect_inlining, NULL, 1 }, > { OPT_LEVELS_2_PLUS, OPT_finline_small_functions, NULL, 1 }, > { OPT_LEVELS_2_PLUS, OPT_fpartial_inlining, NULL, 1 }, > { OPT_LEVELS_2_PLUS, OPT_finline_functions, NULL, 1 }, > and -O3 further bumps some parameters: > { OPT_LEVELS_3_PLUS, OPT__param_max_inline_insns_auto_, NULL, 30 }, > { OPT_LEVELS_3_PLUS, OPT__param_early_inlining_insns_, NULL, 14 }, > { OPT_LEVELS_3_PLUS, OPT__param_inline_heuristics_hint_percent_, NULL, > 600 }, > { OPT_LEVELS_3_PLUS, OPT__param_inline_min_speedup_, NULL, 15 }, > { OPT_LEVELS_3_PLUS, OPT__param_max_inline_insns_single_, NULL, 200 }, > > > +@option{-fno-optimize-sibling-calls} (which prevents optimizing sibling > > -fno-optimize-sibling-calls is the default for -O0/-O1/-Og; dunno if we > want to reiterate it. Can't hurt. Here's an updated patch. -- >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 | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 726392409b6..3f2512ce16a 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -16510,6 +16510,16 @@ 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{-O0}, @option{-O1}, or @option{-Og} (which, for instance, prevent +most function inlining), @option{-fno-optimize-sibling-calls} (which prevents +optimizing sibling and tail recursive calls; this option is implicit for +@option{-O0}, @option{-O1}, or @option{-Og}), 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: 3a9f6d5a8ee490adf9a18f93feaf86542642be7d -- 2.38.1