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.
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.