Re: c++/168: Spurious warning in 2.95.2

[Wolfgang Bangerth <bangerth@ticam.utexas.edu>]

The following reply was made to PR c++/168; it has been noted by GNATS.

From: Wolfgang Bangerth <bangerth@ticam.utexas.edu>
To: gcc-bugs@gcc.gnu.org, <gcc-gnats@gcc.gnu.org>,
   <martin@loewis.home.cs.tu-berlin.de>, <tmwg-gcc@inxservices.com>
Cc:  
Subject: Re: c++/168: Spurious warning in 2.95.2
Date: Tue, 22 Oct 2002 16:48:33 -0500 (CDT)

 This is equally well a C report as a C++ report, since the problem appears 
 with both languages. The questionably code is
 ----------------------------------
 int main () {
   unsigned char      uc;
   unsigned short int usi;
   unsigned int       ui;
   if (uc + usi >= ui);
 }
 ----------------------------------
 and the report is that this issues an error
   t.i:5: warning: comparison between signed and unsigned
 
 As Jason pointed out, this is due to the fact that the left hand side is 
 converted to an integer. I have no opinion about the validity or the 
 warning, people should use casts to avoid this. I just wanted to share the 
 reduced code.
 
 This may be something for value range propagation, since then it would be 
 clear that the left hand side must be positive.
 
 Regards
   Wolfgang
 
 -------------------------------------------------------------------------
 Wolfgang Bangerth              email:           bangerth@ticam.utexas.edu
                                www: http://www.ticam.utexas.edu/~bangerth