-fsanitize=undefined behavior

-fsanitize=undefined behavior

[Tom N]

The man page for -fsanitize=undefined lists a bunch of sub-options (eg. -fsanitize=shift, -fsanitize=shift-exponent, etc).  If I include -fsanitize=undefined does it enable all of the sub-options, or none, or something in between?  If it doesn't enable all sub-options, is there an easy way to do that short of specifying all of them?


TIA!

Re: -fsanitize=undefined behavior

[Jonathan Wakely]

On Thu, 30 Apr 2020 at 22:27, Tom N <nospam@codesniffer.com> wrote:
>
> The man page for -fsanitize=undefined lists a bunch of sub-options (eg. -fsanitize=shift, -fsanitize=shift-exponent, etc).  If I include -fsanitize=undefined does it enable all of the sub-options, or none, or something in between?  If it doesn't enable all sub-options, is there an easy way to do that short of specifying all of them?

The man page says:

"Unlike other similar options, -fsanitize=float-divide-by-zero is not
enabled by -fsanitize=undefined" and "Unlike other similar options,
-fsanitize=float-cast-overflow is not enabled by -fsanitize=undefined"

So it seems reasonable to assume that all the other suboptions are
enabled by -fsanitize=undefined, and if you want *all* of them then
use -fsanitize=undefined -fsanitize=float-divide-by-zero
-fsanitize=float-cast-overflow

Re: -fsanitize=undefined behavior

[Tom N]

> On April 30, 2020 at 5:57 PM Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> The man page says:
> "Unlike other similar options, -fsanitize=float-divide-by-zero is not enabled by -fsanitize=undefined" and "Unlike other similar options,-fsanitize=float-cast-overflow is not enabled by -fsanitize=undefined"
> So it seems reasonable to assume that all the other suboptions are enabled by -fsanitize=undefined, and if you want *all* of them then use -fsanitize=undefined -fsanitize=float-divide-by-zero-fsanitize=float-cast-overflow

Thanks for the tip.  Any reason the description of -fsanitize=undefined doesn't include something like, "If the -fsanitize=undefined option is enabled all sub-options will be enabled unless otherwise specified." so it's clear?

Re: -fsanitize=undefined behavior

[Jonathan Wakely]

On Thu, 30 Apr 2020 at 23:58, Tom N <nospam@codesniffer.com> wrote:
>
> > On April 30, 2020 at 5:57 PM Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> > The man page says:
> > "Unlike other similar options, -fsanitize=float-divide-by-zero is not enabled by -fsanitize=undefined" and "Unlike other similar options,-fsanitize=float-cast-overflow is not enabled by -fsanitize=undefined"
> > So it seems reasonable to assume that all the other suboptions are enabled by -fsanitize=undefined, and if you want *all* of them then use -fsanitize=undefined -fsanitize=float-divide-by-zero-fsanitize=float-cast-overflow
>
> Thanks for the tip.  Any reason the description of -fsanitize=undefined doesn't include something like, "If the -fsanitize=undefined option is enabled all sub-options will be enabled unless otherwise specified." so it's clear?

Probably because nobody has suggested doing that yet. Would you like
to propose a patch for the docs?

The relevant place is here:
https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/doc/invoke.texi;h=527d362533ab503cee9568b27808177977a52ac8;hb=HEAD#l13541

Re: -fsanitize=undefined behavior

[Segher Boessenkool]

Hi!

On Thu, Apr 30, 2020 at 10:57:49PM +0100, Jonathan Wakely via Gcc-help wrote:
> On Thu, 30 Apr 2020 at 22:27, Tom N <nospam@codesniffer.com> wrote:
> >
> > The man page for -fsanitize=undefined lists a bunch of sub-options (eg. -fsanitize=shift, -fsanitize=shift-exponent, etc).  If I include -fsanitize=undefined does it enable all of the sub-options, or none, or something in between?  If it doesn't enable all sub-options, is there an easy way to do that short of specifying all of them?
> 
> The man page says:
> 
> "Unlike other similar options, -fsanitize=float-divide-by-zero is not
> enabled by -fsanitize=undefined" and "Unlike other similar options,
> -fsanitize=float-cast-overflow is not enabled by -fsanitize=undefined"
> 
> So it seems reasonable to assume that all the other suboptions are
> enabled by -fsanitize=undefined, and if you want *all* of them then
> use -fsanitize=undefined -fsanitize=float-divide-by-zero
> -fsanitize=float-cast-overflow

The code (flag-types.h) says
  SANITIZE_UNDEFINED_NONDEFAULT = SANITIZE_FLOAT_DIVIDE | SANITIZE_FLOAT_CAST
                                  | SANITIZE_BOUNDS_STRICT
(and there are no surprises with how it is used).  The
-fsanitize-bounds-strict option is unusual: it *weakens* what
-fsanitize-bounds does!

So yes, only -fsanitize=float-divide-by-zero and
-fsanitize=float-cast-overflow are not enabled by default.


Segher

Re: -fsanitize=undefined behavior

[Tom N]

[-- Attachment #1: Type: text/plain, Size: 1843 bytes --]

> On May 1, 2020 at 7:39 AM Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> 
> On Thu, 30 Apr 2020 at 23:58, Tom N <nospam@codesniffer.com> wrote:>> > On April 30, 2020 at 5:57 PM Jonathan Wakely <jwakely.gcc@gmail.com> wrote:The man page says:"Unlike other similar options, -fsanitize=float-divide-by-zero is not enabled by -fsanitize=undefined" and "Unlike other similar options,-fsanitize=float-cast-overflow is not enabled by -fsanitize=undefined"So it seems reasonable to assume that all the other suboptions are enabled by -fsanitize=undefined, and if you want *all* of them then use -fsanitize=undefined -fsanitize=float-divide-by-zero-fsanitize=float-cast-overflow> Thanks for the tip. Any reason the description of -fsanitize=undefined doesn't include something like, "If the -fsanitize=undefined option is enabled all sub-options will be enabled unless otherwise specified." so it's clear?Probably because nobody has suggested doing that yet. Would you liketo propose a patch for the docs?
> The relevant place is here:https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/doc/invoke.texi;h=527d362533ab503cee9568b27808177977a52ac8;hb=HEAD#l13541

I'd be happy to but unfortunately I'm not familiar with git. (I know...).  But here's an old-style patch off 8.4 if it helps (attached too):

-----
--- gcc-8.4.0/gcc/doc/invoke.texi	2020-03-04 03:30:00.000000000 -0500
+++ gcc-8.4.0_new/gcc/doc/invoke.texi	2020-05-01 13:10:36.517390533 -0400
@@ -11404,7 +11404,8 @@
 @opindex fsanitize=undefined
 Enable UndefinedBehaviorSanitizer, a fast undefined behavior detector.
 Various computations are instrumented to detect undefined behavior
-at runtime.  Current suboptions are:
+at runtime.  If this option is enabled all sub-options listed below will be
+enabled unless otherwise specified. Current suboptions are:
 
 @table @gcctabopt
 
-----

[-- Attachment #2: sanitize_undefined_elaboration_gcc8.4.patch --]
[-- Type: text/x-patch, Size: 537 bytes --]

--- gcc-8.4.0/gcc/doc/invoke.texi	2020-03-04 03:30:00.000000000 -0500
+++ gcc-8.4.0_new/gcc/doc/invoke.texi	2020-05-01 13:10:36.517390533 -0400
@@ -11404,7 +11404,8 @@
 @opindex fsanitize=undefined
 Enable UndefinedBehaviorSanitizer, a fast undefined behavior detector.
 Various computations are instrumented to detect undefined behavior
-at runtime.  Current suboptions are:
+at runtime.  If this option is enabled all sub-options listed below will be
+enabled unless otherwise specified. Current suboptions are:
 
 @table @gcctabopt
 

Re: -fsanitize=undefined behavior

[Jonathan Wakely]

On Fri, 1 May 2020 at 18:13, Tom N <nospam@codesniffer.com> wrote:
>
> > On May 1, 2020 at 7:39 AM Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> >
> > On Thu, 30 Apr 2020 at 23:58, Tom N <nospam@codesniffer.com> wrote:>> > On April 30, 2020 at 5:57 PM Jonathan Wakely <jwakely.gcc@gmail.com> wrote:The man page says:"Unlike other similar options, -fsanitize=float-divide-by-zero is not enabled by -fsanitize=undefined" and "Unlike other similar options,-fsanitize=float-cast-overflow is not enabled by -fsanitize=undefined"So it seems reasonable to assume that all the other suboptions are enabled by -fsanitize=undefined, and if you want *all* of them then use -fsanitize=undefined -fsanitize=float-divide-by-zero-fsanitize=float-cast-overflow> Thanks for the tip. Any reason the description of -fsanitize=undefined doesn't include something like, "If the -fsanitize=undefined option is enabled all sub-options will be enabled unless otherwise specified." so it's clear?Probably because nobody has suggested doing that yet. Would you liketo propose a patch for the docs?
> > The relevant place is here:https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/doc/invoke.texi;h=527d362533ab503cee9568b27808177977a52ac8;hb=HEAD#l13541
>
> I'd be happy to but unfortunately I'm not familiar with git. (I know...).  But here's an old-style patch off 8.4 if it helps (attached too):

That'll do, thanks. I'll do the rest early next week.

Re: -fsanitize=undefined behavior

[Tom N]

> On May 1, 2020 at 2:17 PM Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> 
> That'll do, thanks. I'll do the rest early next week.

Thanks!