The QT-Chooser package on a system I use refused to compile for the longest time. Checking the make.conf file I realized I had both -mtune=atom and -march=atom set for the CFLAGS variable which was causing problems with the package when I attempted to compile it. After changing -mtune to generic (-mtune=generic), I removed -march and emerged @world with only a few minor hiccups.
###-mtune vs. -march
What are these options and how to they effect things?
-mtune and -march are options that can be passed to the GCC compiler at run time in order to specific generate instructions for the machine’s CPU.
-mtune “tunes the generated code for the specified cpu-type.” mtune is magical because it has a “generic” option, which allows the system to compile code that can work on a verity of modern CPUs (IA32/AMD64/EM64T).
-march “allows GCC to generate code that may not run at all on processors other than the one indicated.”
In summary use -mtune=generic if:
- You want your compiled package to work on machines other than your machine;
- To choose a setting that doesn't break on any packages;
- An easy, no hassle compile solution to most packages.
- If you are planning on using distcc.
- You have a specific CPU that code should be compiled for;
- To have the smallest, fastest, lightest binaries specific to the system's CPU.
- If you are not concerned about using Distcc. Both the flags can actually be used together. For the list of all available configuration options (and better explanations than I can provide) see GCC's [i386 and x86-64 Options](https://gcc.gnu.org/onlinedocs/gcc/i386-and-x86-64-Options.html#i386-and-x86-64-Options) page. Maffblaster