clang default options lead to incorrect code

[Bob Wilkinson]

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=33&t=36898

In brief, by default, clang produces code which links with the -lm library to produce incorrect results on the Pi. If clang is invoked with the -mfpu=vfp option, then it produces correct code. However, this fix is not documented in "man clang"

It seems that http://www.raspbian.org/RaspbianFAQ#What_compilation_options_should_be_set_Raspbian_code.3F is not being followed for clang?

[peter green (plugwash)]

It sounds to me like clang is not correctly using the hard float ABI. Using -mfpu=vfp is probablly just masking the real problem by making clang do the square root inline rather than using the math library.

I will bring this up with debian after the wheezy release. In the meantime I would suggest using gcc to build c code (out of interest why were you using clang anyway?).

[peter green (plugwash)]

should be fixed now