|Re: [avr-gcc-list] strange c++ obiect initialization problems (full code included)
|Sun, 12 Jun 2011 18:11:31 +0200
|Mozilla Thunderbird 1.0.7 (Windows/20050923)
Marcin S schrieb:
2011/6/11 Georg-Johann Lay <address@hidden>:Marcin S schrieb:2011/6/9 Georg-Johann Lay <address@hidden>:Marcin S schrieb:Hello there, from time to time i have a strange problems when initializing class objects in file range by their respective constructors, i noted that problem occurs only when that constructors takes pointers to other global objects, tables or something else. Whats the problem? in best scenario object pointer are wrongly set and pointing to some random locations, at worst my program does not start at all (event with my main() func empty) it just hangs here is link to my codehttp://dl.dropbox.com/u/6883398/Lays.tar.bz2 its and eclipse project, simple "make" in project directory should work too.Note that archive contains already compiled program in "Release" directory, this compilation does not work at all! (worst case scenario described above). As I wrote this program incrementaly it stopped working after i added 2 objects inits in layouts.cppCLayPGMString minTag(minTagData,strMin,true,CLayPGMString::XSMALL); CLayPGMString maxTag(maxTagData,strMax,true,CLayPGMString::XSMALL);strMin and strMax params are pointers to strings in PROGMEM, if i replace it with zeros like CLayPGMStringminTag(minTagData,0,true,CLayPGMString::XSMALL); CLayPGMStringmaxTag(maxTagData,0,true,CLayPGMString::XSMALL); program starts again. Other important thing noted is, when I initialise those objects in file range with their default, empty constructors and then set needed pointers at run time (for example right after main() function) everything works too. I ran out of ideas what could be wrong, maybe wrong code, I'm open to any suggestions. I'm using avr-gcc-4.5.2 on gentoo linux, also checked on stable 4.4 and it behaves exactly the same way. MarcinDo you see r20 used in one of the functions? Reminds me of http://gcc.gnu.org/PR45263 which is not yet backported toavr-gcc < 4.6 JohannHej Johann,I'm not sure if i checked it correctly, I've opened .lss file corresponding to my program and yes, there are some r20operations in this function. Excuse me my lack of knowledge of low lvl stuff, but You think this might cause the problem?That depends on the hardware you use. The problem will not occur on devices <= 64 kib flash. Look at the code again. In the startup code that runs before main you might see use of r20 around calls to you function. Note that these calls will be indirect, so searching for symbol will not help. Using r20 that way in startup can cause problems because is is callee-used register and the callee can clobber it, leaving its content in a mess in startup code.MarcinJohannHi, It's atmega128, so r20 still is a main suspect.Note that these calls will be indirect, so searching for symbol will not help.Umm, then I'm afraid I dont know how to check it. Btw. I tried to confirm this thinking by building 4.6.1 avr-gcc but i think its buggy atm (dwarf2 bug) and i am unable to build any
Yes, that's PR48459: DWARF is unusable in current 4.6 and 4.7, so using DWARF or configuring with --with-dwarf2 will abort.
If you build the compiler on your own, you can simply copy ./gcc/config/avr/libgcc.S from 4.6 or 4.7 into your 4.5 sources. Or you can build 4.6 without dwarf and copy the generated libgcc.a's in respective places in your installed compiler (no matter if win32 or linux).
project with it. I'll wait till it will be usable and let You know. Marcin.
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