[Bug libstdc++/19955] New: Second std::ctype<char>::narrow() does not call std::ctype<char>::do_narrow()

[jgrimm2 at us dot ibm dot com]

Software Environment:
Linux 2.6.9-5.EL #1 SMP Wed Jan 5 19:23:58 EST 2005 ppc64 ppc64 ppc64 
GNU/Linux                                                        

gcc version 3.4.3 20041212 
(**but seems to be in 3.4.4 and 4.0 code too).

Steps to Reproduce:
1. Source File:
t.C
---
#include <locale>

class myctype : public std::ctype<char> 
{
protected:
    const char* do_narrow(const char* lo, const char* hi, char dflt, char* to) 
const 
       {
       for (int i=0;lo!=hi;++lo,++to,++i)
          {
          *to=*lo+i;      
          }
       return hi;
       }
};

int main() 
{
    myctype mc;
    const char input []      = "abcd";
    const char input1 []     = "abcd";
    char tmp[sizeof(input)]  = {0};
    char tmp1[sizeof(input1)]= {0};
    
    mc.narrow(input, input + sizeof(input), '*', tmp);
    printf("tmp is: %s\n",tmp);

    mc.narrow(input1, input1 + sizeof(input1), '*', tmp1);
    printf("tmp1 is: %s\n",tmp1);
    return 0;
}
-----------------------------------------------------------
2. Execute command:
/usr/bin/g++ t.C  
a.out

Actual Results:
tmp is: aceg  
tmp1 is: abcd 

Expected Results:
tmp is: aceg  
tmp1 is: aceg 

-------------------------------------------------------
This change in behavior seems to have come in via this patch:

  http://gcc.gnu.org/ml/gcc-patches/2003-12/msg01106.html

,with the changes to locale_facet2.h


Now, there is a protected _M_narrow_ok member that seems to control whether that
memcpy path should be taken.  Maybe the logic for setting _M_narrow_ok needs a
fixing.  The memcpy path should only be taken when it is discovered that the
narrowing operation does not do anything.  Otherwise, it should use the
narrowing cache (or just call do_narrow())

-- 
           Summary: Second std::ctype<char>::narrow() does not call
                    std::ctype<char>::do_narrow()
           Product: gcc
           Version: 3.4.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libstdc++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jgrimm2 at us dot ibm dot com
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19955