> -----Original Message----- > From: Martin Sebor [mailto:[EMAIL PROTECTED] On Behalf Of Martin Sebor > Sent: Saturday, March 22, 2008 4:47 PM > To: dev@stdcxx.apache.org > Subject: Re: [PATCH] STDCXX-423 LIMITS.cpp assumes integers with no > padding bits > > Sorry Scott, I'm still not sure this is completely correct. > > According to 7.18.1.1 of C99, "The typedef name intN_t designates > a signed integer type with width N, no padding bits, and a two's > complement representation." > > Can you point me to the part of the patch that checks that each > of the exact-width types has no padding bits and that it uses > a two's complement representation? > > A few more comments are inline... > > Scott Zhong wrote: > > Index: LIMITS.cpp > > =================================================================== > > --- LIMITS.cpp (revision 638996) > > +++ LIMITS.cpp (working copy) > > @@ -223,7 +223,19 @@ > > return bits; > > } > > > > +template <class T> > > +unsigned compute_type_bits() > > +{ > > + T max = T (one); > > + T current = T(one); > > + int bits = 1; > > > > + for (; T (current * 2) > max; current *=2, max *= 2, bits++) { } > > + > > + return bits; > > +} > > This function computes the number of bits in the value representation > of the type T. We also need to compute the number of bits in the object > representation of the type (i.e., sizeof(T) * CHAR_BIT). Only if the > two match, and when (no_twos_complement == 0) holds can we define > the exact-width types. > > > + > > + > > // used to compute the size of a pointer to a member function > > struct EmptyStruct { }; > > > > @@ -397,6 +409,12 @@ > > // 1 for a 16-bit integer, etc) > > int width_bits = 0; > > > > + // store exact bit size of each type > > + int ushort_bits = compute_type_bits<unsigned short> (); > > + int uint_bits = compute_type_bits<unsigned int> (); > > + int ulong_bits = compute_type_bits<unsigned long> (); > > + int ullong_bits = compute_type_bits<unsigned LLong> (); > > The last line needs to be guarded in case long long is not > recognized as a type (e.g., EDG eccp in strict mode). > > Martin >
Martin, the macro LLong already takes care of this.
