From:	wemccaug AT prairienet DOT org (Wendy E. McCaughrin)
Newsgroups:	comp.os.msdos.djgpp
Subject:	no copy-ctor for temps
Lines:	34
Message-ID:	<eb8J3.1214$%K6.36@firefly>
Date:	Fri, 01 Oct 1999 19:45:14 GMT
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To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp
Reply-To:	djgpp AT delorie DOT com

 The following example shows that 'gxx' will not invoke a copy-ctor
 for temporaries, only for variables.

#include <iostream.h>
#include <string.h>

 class Overflow
 { char mssg[80];
   public:
      Overflow( char* ccp ) { strcpy(mssg,ccp); }
      Overflow( const Overflow& ovfl )   // must be 'const' !
      { cerr << "copy ctor: ";  strcpy(mssg,ovfl.mssg); }
      void Report() { cerr << mssg; }
 };

 void TstCpy( Overflow );    // call by value

 int main()
 { Overflow of = " I am a variable\n";
   TstCpy(of);   // passing a variable: copy-ctor invoked
   TstCpy(Overflow(" I am a temporary\n"));  // passing temp: no copy-ctor
   return 0;
 }


 void TstCpy(Overflow ovrflw)
 { ovrflw.Report(); }
 

 When compiled and run, the output is:

 copy ctor: I am a variable  (indicating call of copy-ctor)
 I am a temporary            (defaults to bit-wise copy)

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