Re: [Valgrind-users] mysterious failures when using valgrind

[John R. <jr...@Bi...>]

> __float128 exp10(__float128);
> 
> When that routine is called with a negative argument, the return value 
> changes when I run the code through valgrind, e.g.
> 
> -20 3fbc79ca10c9242235d511e976394d7a (without valgrind)
> -20 3fbc79ca10c9240e12445f2000000000 (with valgrind)
> 
> The -20 is the argument for exp10() and was obviously converted to 
> __float128, and the return value is printed here in hex format. 
> Initially I thought that the lowest 64 bits were mangled, but from this 
> example you can see that it is a bit more (the lowest 70 bits differ). 

This is a bug in memcheck.  Please file a bug report.
Construct a short test case program (15 lines or so)
which reproduces the output above.  Then go to the main page
http://www.valgrind.org/ , click on the Bug Reports link
(left column under Contact), describe the problem (much as above),
copy+paste the output, and attach the test case program.
Please also include the versions of valgrind, compiler, C/math library,
and operating system; and kind of hardware.
Thank you.

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