I had a quick look at this. Some errors stem from using int instead of
size_t when defining the variable receiving the return value.
eg line 200 of inifile,cc should be defined as :
size_t newLinePos; /* position of
newline to strip */
But where the string is truncated it seems the strlen has already been
calculated and we are only copying the required characters into a fixed
length buffer so we clearly do know what we are doing. Disabling the
warning can be done with:
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wstringop-truncation"
//
// some code that generates warnings
//
#pragma GCC diagnostic pop
eg. by placing the first 2 lines at the top of inivar.c and the last line
at the end of the file to restore the default error handling, warnings are
no longer displayed.
To my mind, that is the preferred solution as adding obfuscated code to
avoid a warning is worse than the error.
The main thing is we ensure all warnings are reviewed and where the code
can't be corrected without obfuscation, the warning is suppressed for that
section of code.
Rod Webster
*1300 896 832*
+61 435 765 611
Vehicle Modifications Network
www.vehiclemods.net.au
On Sat, 12 Feb 2022 at 07:39, Andy Howell <a...@gamubaru.com> wrote:
>
> On 2/11/22 09:10, Jared McLaughlin wrote:
> > Andy,
> >
> > I'm a reasonable C/C++ programmer as well. I'd be willing to be a hunting
> > partner if you want to go bug hunting together. Did you build on a fresh
> OS
> > install?
> >
> > Jared
>
> Jared,
>
> No, I'm just building this on my Ubuntu 21.10 laptop. I'm using gcc
> 11.2.0 to compile it. That may spit out more warnings that what Buster
> uses. I don't know.
>
> I'd welcome help on it. I'm open to better ways to handle errors like this:
>
> Compiling hal/user_comps/mb2hal/mb2hal_init.c
> In file included from /usr/include/string.h:519,
> from hal/user_comps/mb2hal/mb2hal.h:4,
> from hal/user_comps/mb2hal/mb2hal_init.c:1:
> In function ‘strncpy’,
> inlined from ‘init_mb_links’ at
> hal/user_comps/mb2hal/mb2hal_init.c:717:17:
> /usr/include/x86_64-linux-gnu/bits/string_fortified.h:95:10: warning:
> ‘__builtin_strncpy’ output may be truncated copying 16 bytes from a
> string of length 16 [-Wstringop-truncation]
> 95 | return __builtin___strncpy_chk (__dest, __src, __len,
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 96 | __glibc_objsize (__dest));
> | ~~~~~~~~~~~~~~~~~~~~~~~~
>
> The code in question, with my 'fix' is:
>
> else { //tcp
> strncpy(this_mb_link->lp_tcp_ip,
> this_mb_tx->cfg_tcp_ip, sizeof(this_mb_tx->cfg_tcp_ip)-1);
> + this_mb_link->lp_tcp_ip[sizeof(this_mb_tx->cfg_tcp_ip)-1] ='\0';
> this_mb_link->lp_tcp_port=this_mb_tx->cfg_tcp_port;
>
> Terminating the string makes the compiler happy, even though is only
> required when the source string is exactly n bytes long.
>
> That solution works. It does not cope with possible truncation of the
> source string. I don't know the code enough to know which areas are time
> sensitive, so I wasn't thinking of more CPU intensive fixes like
> computing all the lengths and error checking.
>
> My main aim is to reduce the warnings, so that when new warnings pop up,
> they get attention and dwelt with quickly. Even if its only tell the
> compiler "don't worry, we know what we're doing."
>
> Andy
>
>
> >
> > On Thu, Feb 10, 2022, 4:50 PM Andy Howell <a...@gamubaru.com> wrote:
> >
> >> On 2/10/22 06:10, Steffen Möller wrote:
> >>> On 10.02.22 07:28, Phill Carter wrote:
> >>>>> On 10 Feb 2022, at 4:14 pm, Andy Howell <a...@gamubaru.com> wrote:
> >>>>>
> >>>>>
> >>>>> On 2/9/22 14:46, andy pugh wrote:
> >>>>>> On Wed, 9 Feb 2022 at 20:21, Andy Howell <a...@gamubaru.com> wrote:
> >>>>>>
> >>>>>>> My background is in c/c++ development under UNIX/Linux. I know bit
> of
> >>>>>>> python. I don't have the experience to work on the low level
> >>>>>>> internals.
> >>>>>> How about this one?
> >>>>>> https://github.com/LinuxCNC/linuxcnc/issues/1438
> >>>>>>
> >>>>>> A text search on the pin name would find the right part of the code,
> >>>>>> and would let you find where the associated internal variable is
> >>>>>> updated.
> >>>>>>
> >>>>>> (This is internals, but with code to copy from)
> >>>>> Thanks. That sounds like a good problem to start with. I will have a
> >>>>> look at the code and comment under the issue.
> >>>> I do have a PR ready to submit but I am happy to hold off.
> >>> That sounds so nice and so wrong at the same time. I suggest to submit
> >>> the PR and you have already found a reviewer.
> >>>
> >>> @Andy, I am currently on a mission to render the C/C++ sources
> >>> cppcheck-clean. You see a few PRs on this already - and one issue that
> I
> >>> could not solve with a quick patch that I think is a bug. I personally
> >>> use this to get acquainted with the code base a bit more - have started
> >>> with src/hal/* and src/emc/* and have just about completed that, I
> >>> think. But there is more.
> >>>
> >>> Many thanks and greetings
> >>> Steffen
> >>>
> >> Steffen,
> >>
> >> I could certainly work on that. I just compiled LinuxCNC for the first
> >> time in a very long time. There were lots of compiler warnings,
> >> particularly around strncpy and snprintf. I think those would be worth
> >> looking into. It would be nice to fix the code to remove the warnings,
> >> or turn warnings off where needed when they are clearly a false
> >> positive. For example,
> >>
> >> hal/user_comps/mb2hal/mb2hal_init.c:187:55: warning: ‘%02d’ directive
> >> output may be truncated writing between 2 and 10 bytes into a region of
> >> size 7 [-Wformat-truncation=]
> >> 187 | snprintf(section, sizeof(section)-1, "TRANSACTION_%02d",
> >> mb_tx_num);
> >> | ^~~~
> >> hal/user_comps/mb2hal/mb2hal_init.c:187:42: note: directive argument in
> >> the range [0, 2147483647]
> >> 187 | snprintf(section, sizeof(section)-1, "TRANSACTION_%02d",
> >> mb_tx_num);
> >> | ^~~~~~~~~~~~~~~~~~
> >>
> >> The local 'section' buffer there is 20 bytes. Although it might never be
> >> an issue in practice, increasing the buffer size will make sure it never
> >> is and remove the warning. Maybe we can get to a point where we can
> >> treat warnings as errors.
> >>
> >> Does that sound worth pursuing?
> >>
> >>> _______________________________________________
> >>> Emc-developers mailing list
> >>> Emc-developers@lists.sourceforge.net
> >>> https://lists.sourceforge.net/lists/listinfo/emc-developers
> >>
> >> _______________________________________________
> >> Emc-developers mailing list
> >> Emc-developers@lists.sourceforge.net
> >> https://lists.sourceforge.net/lists/listinfo/emc-developers
> >>
> > _______________________________________________
> > Emc-developers mailing list
> > Emc-developers@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-developers
>
>
> _______________________________________________
> Emc-developers mailing list
> Emc-developers@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-developers
>
_______________________________________________
Emc-developers mailing list
Emc-developers@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-developers
