ctor style cast vs c style cast

[Peter A. Felvegi]

hello all,

today i've run into this: if i cast a double value to an unsigned int
using the C style cast when passing it to printf, it's fine. however, if
i use the ctor style cast, i get a compile error. in theory, these two
should do the same: create a temporary unsigned int, and assign the
double to it after conversion, just the syntax is different. made a
little test, see attachment. plain int's are ok, but when qualified with
signed/unsigned the error occurs.

i can't judge whether this is an error or not, please clarify.

$ gcc -v
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v
--enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr
--enable-shared --with-system-zlib --libexecdir=/usr/lib
--without-included-gettext --enable-threads=posix --enable-nls
--program-suffix=-4.1 --enable-__cxa_atexit --enable-clocale=gnu
--enable-libstdcxx-debug --enable-mpfr --enable-checking=release
x86_64-linux-gnu
Thread model: posix
gcc version 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)

regards, p


void f(int i)
{
}

void g(unsigned int j)
{
}

class X
{
public:
	 X(double);
};

void t()
{
	// named variables with ctor syntax : all ok
	int          i1(1.0);
	signed int   i2(1.0);
	unsigned int i3(1.0);

	const int          ci1(1.0);
	const signed int   ci2(1.0);
	const unsigned int ci3(1.0);

	// unnamed temporaries with ctor syntax
	int(1.0);
	signed int(1.0);   // error
	unsigned int(1.0); // error

	const int(1.0);          // error
	const signed int(1.0);   // error
	const unsigned int(1.0); // error

	// unnamed temporaries with C style cast
	(signed int)(1.0);
	(unsigned int)(1.0); 
	(const signed int)(1.0);
	(const unsigned int)(1.0);

	// named variable and unnamed temporary of class X
	X x(1.0);
	X(1.0);

	const X cx(1.0);
	const X(1.0);

	// new ctor style casts
	f(int(1.0));
	f(signed int(1.0));  // error
	g(unsigned int(1.0)); // error

	// old c style casts
	f((int)1.0);
	f((signed int)1.0);
	g((unsigned int)1.0);
}

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