[Bug c++/55254] New: Warn for implicit conversion from int to char

[Bug c++/55254] New: Warn for implicit conversion from int to char

[david at doublewise dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55254

             Bug #: 55254
           Summary: Warn for implicit conversion from int to char
    Classification: Unclassified
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: david@doublewise.net


I sometimes want to construct a string with n copies of a char c. However, I
frequently get the order of elements in the constructor mixed up. Rather than
saying std::string(80, '='), I accidentally call std::string('=', 80).

To me, it seems like the underlying issue here is that gcc does not warn for
implicit conversion from int to char. Whenever I assign a literal to a char, I
always assign something wrapped in single quotes, never an integer literal.

However, I would suggest that perhaps this warning should have two levels. The
first level would only warn for char. The second level would warn for char,
signed char, and unsigned char. The reason for this separation is that int8_t
is a typedef for signed char and uint8_t is a typedef for unsigned char (on
most platforms), and those are regularly used as "small integers" (I use them
extensively in space-sensitive code). My experience is that when people use a
signed / unsigned char explicitly, or one of the typedefs in cstdint /
stdint.h, they are not used as actual characters, but bytes / small numbers,
and in that case, assigning from an integer wouldn't be incorrect.

[Bug c++/55254] Warn for implicit conversion from int to char

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55254

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-11-14 17:12:23 UTC ---
An alternative would be to warn for conversion from the char literal '=' to an
integer type.  If you said '=' chances are you meant it to be a char, not
int('='). That wouldn't help if using a non-literal char though.

Or, when calling a function with two or more arguments, if all arguments
require an implicit conversion and re-ordering the arguments would require
fewer implicit conversions, suggest the arguments might be ordered incorrectly.
 That would be more work (to implement, at on every compilation)

[Bug c++/55254] Warn for implicit conversion from int to char

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55254

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement