libcamera: v4l2_subdevice: Work around false positive warning
diff mbox series

Message ID 20250114143622.28803-1-laurent.pinchart@ideasonboard.com
State Accepted
Commit b01918978c8281d344d5408b3a13aab9e5af4b5d
Headers show
Series
  • libcamera: v4l2_subdevice: Work around false positive warning
Related show

Commit Message

Laurent Pinchart Jan. 14, 2025, 2:36 p.m. UTC 
gcc 13.3.0, as provided by buildroot 2024.11.1, chokes when compiling
v4l2_subdevice.cpp with ASan enabled, due to the usage of the C++
standard library regex header:

In file included from /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/functional:59,
                 from ../../include/libcamera/base/utils.h:12,
                 from ../../include/libcamera/base/log.h:15,
                 from ../../include/libcamera/internal/v4l2_subdevice.h:20,
                 from ../../src/libcamera/v4l2_subdevice.cpp:8:
In constructor ‘std::function<_Res(_ArgTypes ...)>::function(std::function<_Res(_ArgTypes ...)>&&) [with _Res = bool; _ArgTypes = {char}]’,
    inlined from ‘std::__detail::_State<_Char_type>::_State(std::__detail::_State<_Char_type>&&) [with _Char_type = char]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:149:4,
    inlined from ‘std::__detail::_StateIdT std::__detail::_NFA<_TraitsT>::_M_insert_subexpr_begin() [with _TraitsT = std::__cxx11::regex_traits<char>]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:281:24:
/host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/std_function.h:405:42: error: ‘*(std::function<bool(char)>*)((char*)&__tmp + offsetof(std::__detail::_StateT, std::__detail::_State<char>::<unnamed>.std::__detail::_State_base::<unnamed>)).std::function<bool(char)>::_M_invoker’ may be used uninitialized [-Werror=maybe-uninitialized]
  405 |       : _Function_base(), _M_invoker(__x._M_invoker)
      |                                      ~~~~^~~~~~~~~~
In file included from /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/regex:65,
                 from ../../src/libcamera/v4l2_subdevice.cpp:11:
/host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h: In member function ‘std::__detail::_StateIdT std::__detail::_NFA<_TraitsT>::_M_insert_subexpr_begin() [with _TraitsT = std::__cxx11::regex_traits<char>]’:
/host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:279:17: note: ‘__tmp’ declared here
  279 |         _StateT __tmp(_S_opcode_subexpr_begin);
      |                 ^~~~~
In member function ‘bool std::_Function_base::_M_empty() const’,
    inlined from ‘std::function<_Res(_ArgTypes ...)>::operator bool() const [with _Res = bool; _ArgTypes = {char}]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/std_function.h:574:25,
    inlined from ‘std::function<_Res(_ArgTypes ...)>::function(std::function<_Res(_ArgTypes ...)>&&) [with _Res = bool; _ArgTypes = {char}]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/std_function.h:407:6,
    inlined from ‘std::__detail::_State<_Char_type>::_State(std::__detail::_State<_Char_type>&&) [with _Char_type = char]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:149:4,
    inlined from ‘std::__detail::_StateIdT std::__detail::_NFA<_TraitsT>::_M_insert_subexpr_begin() [with _TraitsT = std::__cxx11::regex_traits<char>]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:281:24:
/host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/std_function.h:247:37: error: ‘*(const std::_Function_base*)((char*)&__tmp + offsetof(std::__detail::_StateT, std::__detail::_State<char>::<unnamed>.std::__detail::_State_base::<unnamed>)).std::_Function_base::_M_manager’ may be used uninitialized [-Werror=maybe-uninitialized]
  247 |     bool _M_empty() const { return !_M_manager; }
      |                                     ^~~~~~~~~~
/host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h: In member function ‘std::__detail::_StateIdT std::__detail::_NFA<_TraitsT>::_M_insert_subexpr_begin() [with _TraitsT = std::__cxx11:
/host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:279:17: note: ‘__tmp’ declared here
  279 |         _StateT __tmp(_S_opcode_subexpr_begin);
      |                 ^~~~~

This is a false positive that previously occurred with gcc 12.1.0 and
was fixed in 12.2 (see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105562),
and it seems to have now reappeared. The bug report indicates that the
probability of such false positives increase when using sanitizers. As
this isn't caught by CI, which compiles libcamera with gcc 13.3.0, the
chance that such compilation failures will appear in environments
without a clear pattern is relatively high. Work around the problem by
disabling the warning around the inclusiong of the regex header.

If the regex header needs to be included in other source files, creating
a wrapped in libcamera-base may be a cleaner alternative.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 src/libcamera/v4l2_subdevice.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)


base-commit: 2ae7b2ff7438a4deecff2a8b5de685cc14e5cd44

Comments

Stefan Klug Jan. 20, 2025, 8:10 a.m. UTC | #1 
Hi Laurent,

Thank you for the patch. 

On Tue, Jan 14, 2025 at 04:36:22PM +0200, Laurent Pinchart wrote:
> gcc 13.3.0, as provided by buildroot 2024.11.1, chokes when compiling
> v4l2_subdevice.cpp with ASan enabled, due to the usage of the C++
> standard library regex header:
> 
> In file included from /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/functional:59,
>                  from ../../include/libcamera/base/utils.h:12,
>                  from ../../include/libcamera/base/log.h:15,
>                  from ../../include/libcamera/internal/v4l2_subdevice.h:20,
>                  from ../../src/libcamera/v4l2_subdevice.cpp:8:
> In constructor ‘std::function<_Res(_ArgTypes ...)>::function(std::function<_Res(_ArgTypes ...)>&&) [with _Res = bool; _ArgTypes = {char}]’,
>     inlined from ‘std::__detail::_State<_Char_type>::_State(std::__detail::_State<_Char_type>&&) [with _Char_type = char]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:149:4,
>     inlined from ‘std::__detail::_StateIdT std::__detail::_NFA<_TraitsT>::_M_insert_subexpr_begin() [with _TraitsT = std::__cxx11::regex_traits<char>]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:281:24:
> /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/std_function.h:405:42: error: ‘*(std::function<bool(char)>*)((char*)&__tmp + offsetof(std::__detail::_StateT, std::__detail::_State<char>::<unnamed>.std::__detail::_State_base::<unnamed>)).std::function<bool(char)>::_M_invoker’ may be used uninitialized [-Werror=maybe-uninitialized]
>   405 |       : _Function_base(), _M_invoker(__x._M_invoker)
>       |                                      ~~~~^~~~~~~~~~
> In file included from /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/regex:65,
>                  from ../../src/libcamera/v4l2_subdevice.cpp:11:
> /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h: In member function ‘std::__detail::_StateIdT std::__detail::_NFA<_TraitsT>::_M_insert_subexpr_begin() [with _TraitsT = std::__cxx11::regex_traits<char>]’:
> /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:279:17: note: ‘__tmp’ declared here
>   279 |         _StateT __tmp(_S_opcode_subexpr_begin);
>       |                 ^~~~~
> In member function ‘bool std::_Function_base::_M_empty() const’,
>     inlined from ‘std::function<_Res(_ArgTypes ...)>::operator bool() const [with _Res = bool; _ArgTypes = {char}]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/std_function.h:574:25,
>     inlined from ‘std::function<_Res(_ArgTypes ...)>::function(std::function<_Res(_ArgTypes ...)>&&) [with _Res = bool; _ArgTypes = {char}]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/std_function.h:407:6,
>     inlined from ‘std::__detail::_State<_Char_type>::_State(std::__detail::_State<_Char_type>&&) [with _Char_type = char]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:149:4,
>     inlined from ‘std::__detail::_StateIdT std::__detail::_NFA<_TraitsT>::_M_insert_subexpr_begin() [with _TraitsT = std::__cxx11::regex_traits<char>]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:281:24:
> /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/std_function.h:247:37: error: ‘*(const std::_Function_base*)((char*)&__tmp + offsetof(std::__detail::_StateT, std::__detail::_State<char>::<unnamed>.std::__detail::_State_base::<unnamed>)).std::_Function_base::_M_manager’ may be used uninitialized [-Werror=maybe-uninitialized]
>   247 |     bool _M_empty() const { return !_M_manager; }
>       |                                     ^~~~~~~~~~
> /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h: In member function ‘std::__detail::_StateIdT std::__detail::_NFA<_TraitsT>::_M_insert_subexpr_begin() [with _TraitsT = std::__cxx11:
> /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:279:17: note: ‘__tmp’ declared here
>   279 |         _StateT __tmp(_S_opcode_subexpr_begin);
>       |                 ^~~~~
> 
> This is a false positive that previously occurred with gcc 12.1.0 and
> was fixed in 12.2 (see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105562),
> and it seems to have now reappeared. The bug report indicates that the
> probability of such false positives increase when using sanitizers. As
> this isn't caught by CI, which compiles libcamera with gcc 13.3.0, the
> chance that such compilation failures will appear in environments
> without a clear pattern is relatively high. Work around the problem by
> disabling the warning around the inclusiong of the regex header.
> 
> If the regex header needs to be included in other source files, creating
> a wrapped in libcamera-base may be a cleaner alternative.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Looking at the bug report (especially
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105562#c29 ) it might be
sensible to disable -Werror globally when using sanitizers. Let's see
how often it pops up.

Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com> 

Cheers,
Stefan

> ---
>  src/libcamera/v4l2_subdevice.cpp | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/src/libcamera/v4l2_subdevice.cpp b/src/libcamera/v4l2_subdevice.cpp
> index 7a064d87da41..33279654db8c 100644
> --- a/src/libcamera/v4l2_subdevice.cpp
> +++ b/src/libcamera/v4l2_subdevice.cpp
> @@ -8,12 +8,18 @@
>  #include "libcamera/internal/v4l2_subdevice.h"
>  
>  #include <fcntl.h>
> -#include <regex>
>  #include <sstream>
>  #include <string.h>
>  #include <sys/ioctl.h>
>  #include <unistd.h>
>  
> +#pragma GCC diagnostic push
> +#if defined __SANITIZE_ADDRESS__ && defined __OPTIMIZE__
> +#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
> +#endif
> +#include <regex>
> +#pragma GCC diagnostic pop
> +
>  #include <linux/media-bus-format.h>
>  #include <linux/v4l2-subdev.h>
>  
> 
> base-commit: 2ae7b2ff7438a4deecff2a8b5de685cc14e5cd44
> -- 
> Regards,
> 
> Laurent Pinchart
>
Laurent Pinchart Jan. 20, 2025, 8:30 a.m. UTC | #2 
On Mon, Jan 20, 2025 at 09:10:41AM +0100, Stefan Klug wrote:
> Hi Laurent,
> 
> Thank you for the patch. 
> 
> On Tue, Jan 14, 2025 at 04:36:22PM +0200, Laurent Pinchart wrote:
> > gcc 13.3.0, as provided by buildroot 2024.11.1, chokes when compiling
> > v4l2_subdevice.cpp with ASan enabled, due to the usage of the C++
> > standard library regex header:
> > 
> > In file included from /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/functional:59,
> >                  from ../../include/libcamera/base/utils.h:12,
> >                  from ../../include/libcamera/base/log.h:15,
> >                  from ../../include/libcamera/internal/v4l2_subdevice.h:20,
> >                  from ../../src/libcamera/v4l2_subdevice.cpp:8:
> > In constructor ‘std::function<_Res(_ArgTypes ...)>::function(std::function<_Res(_ArgTypes ...)>&&) [with _Res = bool; _ArgTypes = {char}]’,
> >     inlined from ‘std::__detail::_State<_Char_type>::_State(std::__detail::_State<_Char_type>&&) [with _Char_type = char]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:149:4,
> >     inlined from ‘std::__detail::_StateIdT std::__detail::_NFA<_TraitsT>::_M_insert_subexpr_begin() [with _TraitsT = std::__cxx11::regex_traits<char>]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:281:24:
> > /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/std_function.h:405:42: error: ‘*(std::function<bool(char)>*)((char*)&__tmp + offsetof(std::__detail::_StateT, std::__detail::_State<char>::<unnamed>.std::__detail::_State_base::<unnamed>)).std::function<bool(char)>::_M_invoker’ may be used uninitialized [-Werror=maybe-uninitialized]
> >   405 |       : _Function_base(), _M_invoker(__x._M_invoker)
> >       |                                      ~~~~^~~~~~~~~~
> > In file included from /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/regex:65,
> >                  from ../../src/libcamera/v4l2_subdevice.cpp:11:
> > /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h: In member function ‘std::__detail::_StateIdT std::__detail::_NFA<_TraitsT>::_M_insert_subexpr_begin() [with _TraitsT = std::__cxx11::regex_traits<char>]’:
> > /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:279:17: note: ‘__tmp’ declared here
> >   279 |         _StateT __tmp(_S_opcode_subexpr_begin);
> >       |                 ^~~~~
> > In member function ‘bool std::_Function_base::_M_empty() const’,
> >     inlined from ‘std::function<_Res(_ArgTypes ...)>::operator bool() const [with _Res = bool; _ArgTypes = {char}]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/std_function.h:574:25,
> >     inlined from ‘std::function<_Res(_ArgTypes ...)>::function(std::function<_Res(_ArgTypes ...)>&&) [with _Res = bool; _ArgTypes = {char}]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/std_function.h:407:6,
> >     inlined from ‘std::__detail::_State<_Char_type>::_State(std::__detail::_State<_Char_type>&&) [with _Char_type = char]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:149:4,
> >     inlined from ‘std::__detail::_StateIdT std::__detail::_NFA<_TraitsT>::_M_insert_subexpr_begin() [with _TraitsT = std::__cxx11::regex_traits<char>]’ at /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:281:24:
> > /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/std_function.h:247:37: error: ‘*(const std::_Function_base*)((char*)&__tmp + offsetof(std::__detail::_StateT, std::__detail::_State<char>::<unnamed>.std::__detail::_State_base::<unnamed>)).std::_Function_base::_M_manager’ may be used uninitialized [-Werror=maybe-uninitialized]
> >   247 |     bool _M_empty() const { return !_M_manager; }
> >       |                                     ^~~~~~~~~~
> > /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h: In member function ‘std::__detail::_StateIdT std::__detail::_NFA<_TraitsT>::_M_insert_subexpr_begin() [with _TraitsT = std::__cxx11:
> > /host/aarch64-buildroot-linux-gnu/include/c++/13.3.0/bits/regex_automaton.h:279:17: note: ‘__tmp’ declared here
> >   279 |         _StateT __tmp(_S_opcode_subexpr_begin);
> >       |                 ^~~~~
> > 
> > This is a false positive that previously occurred with gcc 12.1.0 and
> > was fixed in 12.2 (see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105562),
> > and it seems to have now reappeared. The bug report indicates that the
> > probability of such false positives increase when using sanitizers. As
> > this isn't caught by CI, which compiles libcamera with gcc 13.3.0, the
> > chance that such compilation failures will appear in environments
> > without a clear pattern is relatively high. Work around the problem by
> > disabling the warning around the inclusiong of the regex header.
> > 
> > If the regex header needs to be included in other source files, creating
> > a wrapped in libcamera-base may be a cleaner alternative.
> > 
> > Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> 
> Looking at the bug report (especially
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105562#c29 ) it might be
> sensible to disable -Werror globally when using sanitizers. Let's see
> how often it pops up.

I'd like to avoid that as much as possible. Enabling ASan increases
build test coverage in CI. If we disable -Werror, we can as well disable
ASan in build tests.

> Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com> 
> 
> > ---
> >  src/libcamera/v4l2_subdevice.cpp | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/src/libcamera/v4l2_subdevice.cpp b/src/libcamera/v4l2_subdevice.cpp
> > index 7a064d87da41..33279654db8c 100644
> > --- a/src/libcamera/v4l2_subdevice.cpp
> > +++ b/src/libcamera/v4l2_subdevice.cpp
> > @@ -8,12 +8,18 @@
> >  #include "libcamera/internal/v4l2_subdevice.h"
> >  
> >  #include <fcntl.h>
> > -#include <regex>
> >  #include <sstream>
> >  #include <string.h>
> >  #include <sys/ioctl.h>
> >  #include <unistd.h>
> >  
> > +#pragma GCC diagnostic push
> > +#if defined __SANITIZE_ADDRESS__ && defined __OPTIMIZE__
> > +#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
> > +#endif
> > +#include <regex>
> > +#pragma GCC diagnostic pop
> > +
> >  #include <linux/media-bus-format.h>
> >  #include <linux/v4l2-subdev.h>
> >  
> > 
> > base-commit: 2ae7b2ff7438a4deecff2a8b5de685cc14e5cd44

Patch
diff mbox series 

diff --git a/src/libcamera/v4l2_subdevice.cpp b/src/libcamera/v4l2_subdevice.cpp
index 7a064d87da41..33279654db8c 100644
--- a/src/libcamera/v4l2_subdevice.cpp
+++ b/src/libcamera/v4l2_subdevice.cpp
@@ -8,12 +8,18 @@ 
 #include "libcamera/internal/v4l2_subdevice.h"
 
 #include <fcntl.h>
-#include <regex>
 #include <sstream>
 #include <string.h>
 #include <sys/ioctl.h>
 #include <unistd.h>
 
+#pragma GCC diagnostic push
+#if defined __SANITIZE_ADDRESS__ && defined __OPTIMIZE__
+#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
+#endif
+#include <regex>
+#pragma GCC diagnostic pop
+
 #include <linux/media-bus-format.h>
 #include <linux/v4l2-subdev.h>