gcc 4.3.3 compiler options enabled by default

Question

I have moved from gcc version 4.0.3 to 4.3.3 and realized that -mfpmath was set to sse by default in gcc 4.3.3. This actually caused errors in my application. In 4.0.3 the -mfpmath was 387.

I want to know how I can get all the default options enabled by gcc for a given version. How can I dump set of all options used by gcc while compiling. This enables me to compare version 4.0.3 vs 4.3.3.

In general it will be great if I can know a comprehensive list of things need to be checked before going for a version change in gcc .(As this has effect on performance and functionality.)

Answer 1

1. The version I've here of gcc 4.3.3 hasn't the behavior you are complaining about. I compiled it myself so I'm pretty sure that there must be another reason for the change you are seeing than just the gcc version (like compiling for 64 bit which has always used sse AFAIR).

2. gcc has release notes which notifies of behavior changes. They are packaged with gcc source distribution and are available on the web. For gcc 4.3 see http://gcc.gnu.org/gcc-4.3/changes.html.

Answer 2

gcc -Q -v (inputfile)

With just a basic tiny c or cpp file as an input file. Should give you a big list of all the options passed to gcc by default, one of those might be causing sse fp math to be enabled.