Re: Function resolution bug in g++ ?

[Nathan Sidwell <nathan at acm dot org>]

Bill Huey wrote:
> 
> Hello,
> 
> This looks like a bug, so I'm posting my report here.
> 
> I'm getting this nasty error:
> 
>         /usr/home/billh/javasrc_1_3_scsl/hotspot1.3.1/src/share/vm/memory/markSweep.cpp: In
>            static member function `static void MarkSweep::mark_sweep_phase1(jint&, long
>            int)':
>         /usr/home/billh/javasrc_1_3_scsl/hotspot1.3.1/src/share/vm/memory/markSweep.cpp:573: call
>            of overloaded `TraceTime(char[8], bool)' is ambiguous
>         /usr/home/billh/javasrc_1_3_scsl/hotspot1.3.1/src/share/vm/runtime/timer.hpp:64: candidates
>            are: TraceTime::TraceTime(const char*, elapsedTimer*, long int = v_true,
>            long int = v_false)
>         /usr/home/billh/javasrc_1_3_scsl/hotspot1.3.1/src/share/vm/runtime/timer.hpp:63:
>                           TraceTime::TraceTime(const char*, long int = v_true)
>         /usr/home/billh/javasrc_1_3_scsl/hotspot1.3.1/src/share/vm/memory/markSweep.cpp: In
>            static member function `static void MarkSweep::mark_sweep_phase2()':
> 
> from this code:
> 
>         TraceTime tm("phase 2", (bool) PrintGC && Verbose);
you have
#defined bool long int
that '(bool) PrintGC && Verbose' is parsed as ((long int)PrintGC) && Verbose
and in your case is an integral constant expression of value zero. It
also has type bool (C++'s bool, not your #define).
That argument can undergo
	pointer conversion to a null pointer value of type elapsedTimer *
	integral promotion to int, followed by integral conversion to long
those conversions are unordered wrt eachother.
When I try it on what I think your doing,
	void Foo (char const *, int *);
	void Foo (char const *, long);

	int main ()
	{
	  Foo ("hello", false);
	  return 0;
	}
I get 
nathan@manao:557>/usr/local/egcs/sparc-SunOS-5/bin/g++ -c foo2.cc 
foo2.cc: In function `int main()':
foo2.cc:7: call of overloaded `Foo(const char[6], bool)' is ambiguous
foo2.cc:2: candidates are: void Foo(const char*, int*)
foo2.cc:3:                 void Foo(const char*, long int)

nathan

-- 
Dr Nathan Sidwell :: Computer Science Department :: Bristol University
           The voices in my head told me to say this
nathan@acm.org  http://www.cs.bris.ac.uk/~nathan/  nathan@cs.bris.ac.uk