diff mbox series

[v3] docs: Suggest options to improve ASAN stack traces

Message ID Y5JrqSFa/3Z2D4AR@redhat.com
State Committed
Commit 6a07798c6bc602c355a546057187169f79872696
Headers
Series [v3] docs: Suggest options to improve ASAN stack traces |

Commit Message

Marek Polacek Dec. 8, 2022, 10:56 p.m. UTC 
  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(+)


base-commit: 3a9f6d5a8ee490adf9a18f93feaf86542642be7d

Comments

Jakub Jelinek Dec. 8, 2022, 11:11 p.m. UTC | #1 
On Thu, Dec 08, 2022 at 05:56:41PM -0500, Marek Polacek wrote:
> 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.

Ok, thanks.

> 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.

	Jakub
diff mbox series

Patch

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.