NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c++-part2/15305

Internet Message Format | 1996-08-05 | 3.0 KB

Path: news.austin.sar.slb.com!usenet
From: Chad Houston <[e-mail]>
Newsgroups: comp.lang.c++
Subject: [Q] String class problem
Date: Thu, 04 Apr 1996 12:34:54 -0600
Organization: Schlumberger GeoQuest
Message-ID: <[e-mail]>
NNTP-Posting-Host: talkingheads.austin.sar.slb.com
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
X-Mailer: Mozilla 2.01 (X11; I; SunOS 5.4 sun4m)

I've recently hit a compiler snag on the SGI with a string class that we've
been using for a while.  It compiles fine on our Solaris 2.4 compilers, but
not on IRIX 5.3.  Regardless of the platform, maybe someone can recognize an
error in my code.

Any help would be greatly appreciated.

Here's a stripped down version of the class:

     util_string.hh
     1
     2  class util_String
     3  {
     4  public:
     5      util_String(const char*);
     6      util_String(const util_String&);
     7      util_String(int);
     8      util_String(float);
     9      util_String(double);
    10      util_String();
    11      ~util_String() { delete Str; }
    12
    13      util_String& operator=(const util_String&);
    14      util_String& operator+=(const util_String&);
    15      operator char*();
    16
    17  private:
    18      int Length;
    19      char *Str;
    20  };


Here is a short test program which illustrates the compiler problem:

     string_test.cc
     1
     2  #include <util_string.hh>
     3
     4  int
     5  main()
     6  {
     7      int        iVal = 5;
     8      float      fVal = 5.12345;
     9      char       cpSpace[] = " ";
    10      char       cpVal[] = "Test String";
    11      util_String MyString;
    12
    13      MyString = cpVal;
    14      MyString += cpSpace;
    15      MyString += iVal;
    16      // MyString += (util_String) iVal;
    17      // MyString.cps_String::operator+=(iVal);
    18      MyString += cpSpace;
    19      MyString += fVal;
    20  }


The SGI /bin/CC compiler returns the following error:

test(200)% !CC
CC -c -I. string_test.cc
"string_test.cc", line 18: error(3431): more than one operator "+=" matches
          these operands:
            built-in operator "pointer += integer"
            function "cps_String::operator+="
      MyString += iVal;


Apparently, it can't determine that it should use the util_String(int) constructor,
and then call the util_String::operator+=(const util_String&) method.  However, the
file *will* compile if I comment out line 15 in the header file.  That is, if
I remove my method to cast a util_String to a char *.  Is there something wrong
with the syntax of my cast operator, operator char *() ?

Note that the file will also compile if I comment out line 15 in string_test.cc
and use either line 16 or 17.

--
+--------------+
|______________|    Chad Houston                       <[e-mail]>
| Schlumberger |    Senior Software Engineer            CPS-3 Engineering
+--------------+    Austin, TX, USA
    GeoQuest            Phone: [phone]  Fax: [phone]