Hi Robert,
you are right the comments are wrong (should be switched for R__B64),
and in addition we planned to make Long_t always 8 bytes in a portable
way be relying on "long long" for 32 bit environments. However, at the
time many compilers did not support the "long long" type (g++ does).
We will try to revise this code in the coming months with the introduction of
our new automatic shema evolution I/O system.
Cheers, Fons.
On Fri, Nov 03, 2000 at 05:23:06PM -0800, Robert Hatcher wrote:
> I'm confused about the sizeof Long_t. I'm running ROOT:
> * Version 2.25/03 15 September 2000 *
> and g++ gives:
> Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/egcs-2.91.66/specs
> gcc version egcs-2.91.66 19990314/Linux (egcs-1.1.2 release)
>
> In Rtypes.h there is code:
>
> #ifdef R__B64
> typedef int Seek_t; //File pointer
> typedef long Long_t; //Signed long integer 4 bytes
> typedef unsigned long ULong_t; //Unsigned long integer 4 bytes
> #else
> typedef int Seek_t; //File pointer
> typedef long Long_t; //Signed long integer 8 bytes
> typedef unsigned long ULong_t; //Unsigned long integer 8 bytes
> #endif
>
> Here Long_t is always typedef'd to "long" even when long isn't 8 bytes.
> The only difference between these two parts is the comments. I thought
> Long_t was intended to be a uniform size (8 bytes) in a platform
> independent manner -- just like Int_t is 4 bytes even when "int" isn't.
> But even if it isn't the comments are exactly backwards; R__B64
> *isn't* defined for this platform so the second block is the relevant one.
> But there the comments say one should expect a 8 byte Long_t when it isn't.
>
> -robert
>
> Robert W. Hatcher | rhatcher@slac.stanford.edu
> Research Associate | 650.926.3171 [FAX 4001 or 3587]
> Stanford University | PO Box 4349, MS #63, Stanford CA 94309
>
> ============ test_sizeof.C ======================
> #ifndef __CINT__
> #include <iostream.h>
> #endif
>
> void test_sizeof()
> {
>
> #ifdef R__B64
> cout << "R__B64 is defined " << endl;
> #else
> cout << "R__B64 is not defined " << endl;
> #endif
> cout << "sizeof(char) " << sizeof(char) << endl;
> cout << "sizeof(Char_t) " << sizeof(Char_t) << endl;
> cout << "sizeof(short) " << sizeof(short) << endl;
> cout << "sizeof(Short_t) " << sizeof(Short_t) << endl;
> cout << "sizeof(int) " << sizeof(int) << endl;
> cout << "sizeof(Int_t) " << sizeof(Int_t) << endl;
> cout << "sizeof(long) " << sizeof(long) << endl;
> cout << "sizeof(Long_t) " << sizeof(Long_t) << endl;
> cout << "sizeof(float) " << sizeof(float) << endl;
> cout << "sizeof(Float_t) " << sizeof(Float_t) << endl;
> cout << "sizeof(double) " << sizeof(double) << endl;
> cout << "sizeof(Double_t) " << sizeof(Double_t) << endl;
> #ifndef __CINT__
> cout << "sizeof(long long) " << sizeof(long long) << endl;
> #else
> cout << "CINT doesn't recognize 'long long' by default " << endl;
> #endif
> }
--
Org: CERN, European Laboratory for Particle Physics.
Mail: 1211 Geneve 23, Switzerland
E-Mail: Fons.Rademakers@cern.ch Phone: +41 22 7679248
WWW: http://root.cern.ch/~rdm/ Fax: +41 22 7677910
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