[Valgrind-users] Bug in tan(x) function ?

[Brad B. <bra...@se...>]

When I run the attached script I get the following output:

[bradbell@brad-home trash]$ ./valgrind_tan_bug.sh
mkdir valgrind_bug
cd valgrind_bug

cat valgrind_bug.cpp
# include <limits>
# include <cmath>
# include <iostream>
int main(void)
{    float x = std::numeric_limits<float>::max() / float(2);
     std::cout << "x           = " << std::endl;
     std::cout << "std::tan(x) = " << std::tan(x) << std::endl;
     return 0;
}

g++ valgrind_bug.cpp -o valgrind_bug -g -Wall -ansi -pedantic-errors 
-std=c++98 -Wshadow

./valgrind_bug
x           =
std::tan(x) = 1.24272

valgrind ./valgrind_bug
==8289== Memcheck, a memory error detector
==8289== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al.
==8289== Using Valgrind-3.6.1 and LibVEX; rerun with -h for copyright info
==8289== Command: ./valgrind_bug
==8289==
x           =
std::tan(x) = nan
==8289==
==8289== HEAP SUMMARY:
==8289==     in use at exit: 0 bytes in 0 blocks
==8289==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==8289==
==8289== All heap blocks were freed -- no leaks are possible
==8289==
==8289== For counts of detected and suppressed errors, rerun with: -v
==8289== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 15 from 8)

Note: value of tan(x) is different when run with valgrind

uname -a
Linux brad-home.localdomain 2.6.43.8-1.fc15.i686 #1 SMP Mon Jun 4 
20:28:56 UTC 2012 i686 i686 i386 GNU/Linux

valgrind --version
valgrind-3.6.1
g++ --version
g++ (GCC) 4.6.1 20110908 (Red Hat 4.6.1-9)
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[bradbell@brad-home trash]$