[Bug c/109056] New: cppcheck: no warning for suspicious return type

[Bug c/109056] New: cppcheck: no warning for suspicious return type

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109056

            Bug ID: 109056
           Summary: cppcheck: no warning for suspicious return type
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dcb314 at hotmail dot com
  Target Milestone: ---

For the following C code:

unsigned long f( int n)
{
        return n * 1000;
}

where the programmer may have intended using an unsigned long constant
like 1000UL, then static analyser cppcheck can be made to say:

mar7b.cc:4:2: style: int result is returned as long value. If the return value
is long to avoid loss of information, then you have loss of information.
[truncLongCastReturn]
 return n * 1000;

gcc says nothing:

$ ~/gcc/results/bin/gcc -c -g  -O2 -Wall -Wextra mar7b.cc
$ 

The example code is derived from 10 examples in the source code of
linux-6.3-rc1, so the problem does really occur in practice.

[Bug c/109056] cppcheck: no warning for suspicious return type

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109056

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
-Wconversion is needed for this warning in GCC.

[Bug c/109056] cppcheck: no warning for suspicious return type

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109056

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> -Wconversion is needed for this warning in GCC.

Which turns on -Wsign-conversion .

[Bug c/109056] cppcheck: no warning for suspicious return type

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109056

--- Comment #3 from David Binderman <dcb314 at hotmail dot com> ---
(In reply to Andrew Pinski from comment #2)
> Which turns on -Wsign-conversion .

-Wsign-conversion seems close, but not quite right. The problem is
in potential overflow, not sign conversion.

-Woverflow doesn't seem to do anything. Nor does -Wconversion.