On Mon, May 13, 2013 at 03:12:07PM -0700, Simon Glass wrote: > Hi Tom, > > On Thu, Mar 21, 2013 at 7:38 AM, Tom Rini <tr...@ti.com> wrote: > > On Tue, Feb 26, 2013 at 08:10:53AM -0800, Simon Glass wrote: > > > >> Many parts of the U-Boot code base are sprinkled with #ifdefs. This makes > >> different boards compile different versions of the source code, meaning > >> that we must build all boards to check for failures. It is easy to misspell > >> an #ifdef and there is not as much checking of this by the compiler. > >> Multiple > >> dependent #ifdefs are harder to do than with if..then..else. Variable > >> declarations must be #idefed as well as the code that uses them, often much > >> later in the file/function. #ifdef indents don't match code indents and > >> have their own separate indent feature. Overall, excessive use of #idef > >> hurts readability and makes the code harder to modify and refactor. For > >> people coming newly into the code base, #ifdefs can be a big barrier. > >> > >> The use of #ifdef in U-Boot has possibly got a little out of hand. In an > >> attempt to turn the tide, this series includes a patch which provides a way > >> to make CONFIG macros available to C code without using the preprocessor. > >> This makes it possible to use standard C conditional features such as > >> if/then instead of #ifdef. A README update exhorts compliance. > > > > OK, this is true. Looking over the series, a number of the patches are > > just general fixes / improvements that don't depend on the autoconf_... > > work. Lets split this out now and take them in now as they seem like > > reviewable by inspection code. > > Well sorry I didn't make time to get this done last time. I can do > this now or... > > > > > For the approach itself, I'm not sure which is best here. In a lot of > > cases we're trading an #ifdef for adding a level of indent to already > > pretty indented code and that feels like a wash, in terms of readability > > to me. We probably need to re-factor some of the code in question there > > too for readability, then see about using autoconf_... type things, or > > maybe something else. > > I think you are saying to do the rearrangement and clean-up first, > then add autoconf afterwards. I can do that but really I am wondering > what you think of the autoconf concept? The Kconfig stuff is related > here too, but first I would like to decide on what to do with the > #ifdefs.
I think a lot of our #ifdefery is a problem of code that's in need of some love and re-org and cleaning and updating. One of the old style rules I still try and follow is that after a few levels of indent code doesn't read well. Also big nested #ifdefs don't read well. So we're trading one in for the other. But your series showed a lot of places where we can re-factor things to improve readability. So lets go that way. Then we can see if there's still things to improve on, and what dead code we still have around. -- Tom
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