On Thu, Dec 10, 2015 at 3:30 PM, Andrew Haley <aph@xxxxxxxxxx> wrote: > On 12/10/2015 02:26 PM, Mathieu Malaterre wrote: >> On Thu, Dec 10, 2015 at 12:08 PM, Mathieu Malaterre >> <mathieu.malaterre@xxxxxxxxx> wrote: >>> >>> I am trying to track a change in behavior in between gcc 4.4.7 >>> (CentOS/x86_64) and gcc 4.9.2 (fedora/x86_64). The result of a complex >>> computation (floating point involved) is slightly different in between >>> those two. >>> >>> Does anyone knows if there was a major change in floating point >>> computation of std::log, std::pow, std::ceil, std::sqrt or std::exp in >>> between those versions? My input is a raw binary (no ASCII parsing >>> involved anywhere in the code). I've compiled code in debug on both >>> side (only option -g is used nothing else). >>> >>> Sorry if this is very broad, I need pointer to get started. >> >> Just for reference. I've scp'ed the executable file from CentOS over >> my fedora installation and it runs as expected. So the issue is within >> one of the system lib on CentOS (libc/libm/libstdc++6 ?) > > So probably not GCC, then. I'm guessing this is actually glibc. Is there a way to test that for sure. A naive solution like: $ LD_PRELOAD=$HOME/libc.so.6 ./mycode results in relocation error: /home/mathieu/libc.so.6: symbol _dl_starting_up, version GLIBC_PRIVATE not defined in file ld-linux-x86-64.so.2 with link time reference > Surely, though, minor differences are not unexpected? True. I simply need to identify the correct location of the issue now. -- Mathieu
