[yocto] CFLAGS and configurations

[Trevor Woerner]

Hi Khem,

Sorry if this has been asked too many times before, but is there is an
advantage to specifying a whole bunch of CFLAGS for every invocation
of the compiler versus specifying them during the ./configure?

For example, if one ./configures their cross-compiler with things like
-march, -mtune, --sysroot, etc then those will be the defaults. If
nothing is otherwise specified, these ./configure options are what
will be used. But if these things aren't specified at ./configure
time, then every time the cross-compiler is invoked these options need
to be specified.

Looking, roughly, through some of the log.do_compile logs when
cross-compiling applications for the target, and looking at the output
of invoking the cross-compile with the "-v" flag, it appears most of
these flags need to be specified for each invocation of the compiler.
The ./configure specifies the sysroot, for example, but doesn't try to
specify any of the -mtune or -march (etc) flags.

Wouldn't it be easier the other way? That way we don't have to worry
that some component's build isn't clobbering our required CFLAGS?

Do the SDK cross-compilers work the same way? Are they ./configure'd similarly?

Best regards,
    Trevor