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[netCDF #IRQ-325570]: nc_test/large_file.c problem and patch

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  • Subject: [netCDF #IRQ-325570]: nc_test/large_file.c problem and patch
  • Date: Tue, 04 Jan 2011 09:46:18 -0700
Hi Gus,

Sorry for taking so long to respond to your comment and bug fix.
> The large file test program in nc_test/large_file.c seems to have a bug.
> The "int n" number used to provide data via cast to signed char
> overflows the integer range.
> 
> The value of n grows up to the product of:
> 
> NUMRECS+1 = 1+1
> I_LEN+1 = 4104+1
> J_LEN+1 = 1023+1
> K_LEN+1 = 1023+1
> 
> which is a number beyond the maximum "int" value of 2147438648.
> 
> I am not a C programmer, but I would guess also
> that casting integer values above the range of signed
> char [-128,127], or unsigned values in the range [0,255]
> is not guaranteed to be supported by all compilers.
> 
> I am building NetCDF4 on Linux x86_64.
> Somehow the Gnu gfortran and Intel icc compile
> the original code and run without problems.
> However, PGI pgcc breaks down there.
> 
> Here is a patch that I applied to that file which removes the overflow,
> and reduces the integer "n" to range [0,255] to use the cast
> (signed char) n.
> With this patch the test program works in pgcc.
> 
> #####################################
> 
> 129c129,131
> <                    var1[j][k] = n++;
> ---
> >                  var1[j][k] = (signed char) n;
> >                  n++;
> >                  n %= 255;
> 171a174
> >                    n %= 255;

Thanks, I've incorporated a fix into our upcoming snapshot release, and
it should appear in the 4.1.2 release.

--Russ

Russ Rew                                         UCAR Unidata Program
address@hidden                      http://www.unidata.ucar.edu



Ticket Details
===================
Ticket ID: IRQ-325570
Department: Support netCDF
Priority: Critical
Status: Closed