http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47742
Summary: Large Values Increment By 1 When Casting Long to
Double
Product: gcc
Version: 4.1.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: dogbreat...@hotmail.com
When casting some large long values to a double the resultant double values is
1 larger than the long. This can easily be seen with the value for LONG_MAX,
but will even appear with long values as low as 23372036854775807 (and possibly
lower). It is not consistent and does not affect all large longs, but does
appear in a great number of them.
ratscat> gcc -v
Using built-in specs.
Target: x86_64-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --enable-shared --enable-threads=posix
--enable-checking=release --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-libgcj-multifile
--enable-languages=c,c++,objc,obj-c++,java,fortran,ada --enable-java-awt=gtk
--disable-dssi --enable-plugin
--with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre --with-cpu=generic
--host=x86_64-redhat-linux
Thread model: posix
gcc version 4.1.2 20080704 (Red Hat 4.1.2-48)
Program is:
#include <stdlib.h>
#include <stdio.h>
#include <limits.h>
#include <float.h>
int main( int argc, char **argv ) {
long infc = LONG_MAX;
double real_size = (double) infc;
printf( "infc %ld\nreal_size %lf\n", infc, real_size );
exit( 0 );
}
ratscat> gcc -Wall truncfc.c
ratscat> a.out
infc 9223372036854775807
real_size 9223372036854775808.000000
