To condense and summarize: Problem: optiboot, a very small bootloader, grows signficantly in binary size when going from gcc 4.5.2 to gcc 4.5.3. This turns out to be because it "misses" code factoring optimizations in optiboot's main() function, which is declared with attribute "naked" to save space. The missing optimizations are tied to "naked"; in sample programs the optimizations re-appear when the naked attribute is not used.
Root cause: PR42240 is a patch that specifically disables "jump modification" in Naked functions, because they can interfere with proper exit handling of naked functions in .init sections. The .init sections are one of the primary intended uses for "naked", while making main() naked is not a recommended practice (and in fact caused/uncovered other bugs in the optiboot code.) Resolution: optiboot will use the "OS_main" attribute instead of "naked." It doesn't disable the optimization, the resulting code is "small enough", and the attribute is more exactly appropriate and correct as well. It was probably an oversight that OS_main wasn't used in the first place. Thanks to all who assisted, especially Herr Lay, who identified the root cause! BillW _______________________________________________ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org https://lists.nongnu.org/mailman/listinfo/avr-gcc-list
