[avr-gcc-list] Missing "call main()" in startup code

[Dave Harper]

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, preceeded 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?

Thanks,
Dave