Dave Harper wrote: > Target MCU: XMega32A4 > WinAVR: WinAVR-20100110 > Studio: v4.18 Build 716 > > I recently completed initial debug of a bootloader for the above target > device. The bootloader is fairly large and, to keep from overflowing > the 4K bootloader flash area, I used the "-nostartfiles" linker flag to > eliminate the vector table since interrupts are not being used. While > debugging using the Studio debugger, I compiled using the -O0 option to > remove optimizations. The compiler produced normal startup code which, > at the end, "fell" into main(). Once debugging was complete, I > recompiled with -Os. Not surprisingly, the order of the code was > restructured with the main() entry point appearing further down in the > code, proceeded by several functions. What was missing was a call to > the main() entry point at the end of the startup code. When I removed > the -nostartfiles linker option (still using -Os optimization) I found > that the call to main() was included. Unfortunately, inclusion of the > vector table - which uses 376 bytes, just about offsets any savings > gained from the -Os optimization. This puts me very close to the 4K > limit again. I'd really like to have this extra space as the next step > (interaction between the application and bootloader) will use a debug > mechanism which uses values written to an I/O port that are monitored by > a logic analyzer to trace the path of execution, as well as variable > values. While these individual debug statements don't take much room > individually, I will be limited in the number I can put in the code at > any given time. > > Also, as a check, I downloaded the latest Studio 5.0 and recompiled > using it (GCC v4.5.1). Same thing. > > Anyone have any ideas on a workaround that might get me past this problem?
If you kick out the start-up code, you are left alone to add the relevant bits: * Initializing zero-reg and SP * Clean .bss * Set-up .data * Call constructors/destructors * Call main * Call _exit * Initialize vector table For parts of start-up code coming from libgcc, see [1] and search for .init. For parts of start-up code coming from avr-libc see [2], in particular section .init9. [1] http://gcc.gnu.org/viewcvs/trunk/libgcc/config/avr/lib1funcs.S?content-type=text%2Fplain&view=co [2] http://svn.savannah.nongnu.org/viewvc/trunk/avr-libc/crt1/gcrt1.S?root=avr-libc&view=co > Thanks, > Dave Johann _______________________________________________ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org https://lists.nongnu.org/mailman/listinfo/avr-gcc-list
