On Mon, Jun 17, 2013 at 10:21 PM, Gene Smith <gds@xxxxxxxxxxxxx> wrote: > If I compile my embedded program with options "-g -O1" I obtain an elf file > with debug information. I can objcopy the elf file to a binary or hex file > that can be loaded to flash, effectively striping out the debug information > leaving only the optimized code in ROM. > > But if I re-build with options the same except omit the -g option, obviously > I will have no symbols in the elf file making debugging impossible or at > least more difficult. However, when I object copy this elf to a binary or > hex file they are different somewhat than the binary or hex produced with > options -g present. At least with 4.7.3 the main difference, as seen with > objdump, is in the prologue to certain function calls with only a few bytes > different in total code length on a fairly large embedded application (arm). > So -g has some effect on the actual code produced it appears. > > Is this difference expected? Should -g cause changes in the actual code > generated and not just add debug symbols to the elf? Possibly it is related > to the optimization level? I have not checked to see if the results differ > with higher or lower levels than -O1. > > I have seen several opinions regarding this but no authoritative answer. The > gcc manual also does not really answer this. If the only change in the command line options is whether you use -g, you should get exactly the same code. Any difference in code generation is a bug. Please try to file a bug report according to the guidelines at http://gcc.gnu.org/bugs/ . Thanks. Ian
