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[gjetost:~/persist/CCversion] cat bug.c
// Bug in g++ 2.2.2.
// The call f(d) can be resolved either by
//   Derived -> Derived& (trivial, ARM 13.2, p318)
//      -> Base& (standard conversion 4.7)
// or by
//   Derived -> Base& (user-defined convertion Derived::operator Base&())
// According to ARM 13.2, p. 318, paragraph [3]
// "Of sequences not mentined in [2], those with only standard and
// trivial conversions are better than all others."
// Thus the user-defined conversion should not be used.

extern "C" void printf(...);

class Base {
public:
	int i;
	Base(int ii) : i(ii) {};
};

class Derived : private Base {
public:
	Derived(int ii) : Base(ii) {}
	operator Base&();
};

Derived::operator Base&() {
	printf("Derived %d -> Base\n", i);
	Base *b = new Base(100*i);
	return *b;
}

void f(Base &b) {
	printf("f(%d)\n",b.i);
}

main() {
	Derived d(99);
	f(d);
}
[gjetost:~/persist/CCversion] g++ -v bug.c
Reading specs from /usr/gnu/lib/gcc-lib/decstation/2.2.2/specs
gcc version 2.2.2
 /usr/gnu/lib/gcc-lib/decstation/2.2.2/cpp -lang-c++ -v -undef -D__GNUC__=2 -D__GNUG__=2 -D__cplusplus -D__ANSI_COMPAT -DMIPSEL -DR3000 -DSYSTYPE_BSD -D_SYSTYPE_BSD -Dbsd4_2 -Dhost_mips -Dmips -Dultrix -Dunix -D__ANSI_COMPAT -D__MIPSEL__ -D__R3000__ -D__SYSTYPE_BSD__ -D___SYSTYPE_BSD__ -D__bsd4_2__ -D__host_mips__ -D__mips__ -D__ultrix__ -D__unix__ -D__ANSI_COMPAT -D__MIPSEL -D__R3000 -D__SYSTYPE_BSD -D___SYSTYPE_BSD -D__bsd4_2 -D__host_mips -D__mips -D__ultrix -D__unix -D__LANGUAGE_C__ -D__LANGUAGE_C -DLA
NGUAGE_C bug.c /usr/tmp/cca22845.i
GNU CPP version 2.2.2 [AL 1.1, MM 19] DECstation running ultrix
 /usr/gnu/lib/gcc-lib/decstation/2.2.2/cc1plus /usr/tmp/cca22845.i -quiet -dumpbase bug.cc -version -o /usr/tmp/cca22845.s
GNU C++ version 2.2.2 [AL 1.1, MM 19] DECstation running ultrix compiled by GNU C version 2.2.2.
 as -nocpp -EL -v -o bug.o /usr/tmp/cca22845.s
/usr/lib/cmplrs/cc/as0 -v -G 8 -EL -g0 -O1 /usr/tmp/cca22845.s -o /tmp/ctmaa22856 -t /tmp/ctmsta22856 
as0: __4Basei __7Derivedi __opR4Base__7Derived f__FR4Base main 
0.0u 0.1s 0:01 8% 63+67k 0+8io 6pf+0w
/usr/lib/cmplrs/cc/as1 -v -G 8 -p0 -EL -g0 -O1 /tmp/ctmaa22856 -o bug.o -t /tmp/ctmsta22856 
as1: __4Basei __7Derivedi __opR4Base__7Derived f__FR4Base main 
0.0u 0.1s 0:00 17% 91+76k 1+1io 8pf+0w
 /usr/gnu/lib/gcc-lib/decstation/2.2.2/mips-tfile -v -o bug.o /usr/tmp/cca22845.s
mips-tfile version 2.2.2 [AL 1.1, MM 19] DECstation running ultrix
 /usr/gnu/lib/gcc-lib/decstation/2.2.2/ld -EL /usr/lib/cmplrs/cc/crt0.o -L/usr/gnu/lib/gcc-lib/decstation/2.2.2 -L/usr/lib/cmplrs/cc -L/usr/lib/cmplrs/cc -L/usr/gnu/lib bug.o -lg++ -lgcc -lc -lgcc
[gjetost:~/persist/CCversion] a.out
Derived 99 -> Base
f(9900)
[gjetost:~/persist/CCversion] exit

script done on Mon Sep 14 09:38:10 1992