Re: [avr-gcc-list] bug with timer0 interrupt?

[Selvaraj, Senthil_Kumar]

This sounds like the linker script bug that misplaces bss section if the data 
section is empty i.e. if there are no initialized globals.

Jonathan, what version of the linker (GNU binutils) are you using? Does 
-Wl,--section-start=.data=0x800100 help fix the problem?

Sorry about the top posting.

Regards
Senthil

Jonathan Geisler <address@hidden> wrote:


On Fri, Feb 15, 2013 at 01:16:27AM +0100, Georg-Johann Lay wrote:
> Jonathan Geisler schrieb:
> > I'm encountering a strange error with avr-gcc 4.6.3 and 4.7.2 using
> > the timer interrupt.  The code I'm using is attached.  As you can see,
> > I was trying to tie in to the Arduino environment (with Eclipse) so
> > that I could help my students wean off that set of functions to being
> > able to use the hardware directly.
> >
> > When I set up the library, I encountered a strange error and was able
> > to trace it back to this simple program that sets up the timer with a
> > prescalar of 1024 and then increments an unsigned long counter when
> > that timer overflows.  When the counter reaches a specific value, I
> > toggle the built-in LED on the Arduino board connected to PORTB.
> >
> > The strange behavior is that if I initialize the counter to 0, the
> > code doesn't work--appearing to hang.  If I initialize the counter to
> > 1, everything works perfectly.  I have verified that if I make a
> > similar change to the Arduino libraries that the original code begins
> > to work properly.
> >
> > I'm not sure what the exact error is since I can use the Arduino
> > environment on my machine without a problem, but when I try to compile
> > it through Eclipse it gives me this error.  I'll include the build log
> > as an attachment in case particular compiler/linker flags are triggering
> > the error.
>
> When you change count in the ISR and read it in main, the read must be
> atomic.  Otherwise, you may see glitches and phantom values.
>
> It atomic access does not help, you can compare the code generated with
> your Eclipse setup and with your Arduino setup.

The atomic accesses didn't help.  I didn't include that originally
because the Arduino doesn't include them.

For my C code, they appear to be identical.  I didn't compare the
extra code added by the linker.

> You cal also check the generated assembly whether or not it is as you
> expect.  If so, your problem is somewhere else.

The asm code for my C code appears to be correct.  That is what is so
perplexing to me.  Note that the test code is a distillation of what
the Arduino environment does and it quite succinct, but displays the
error quite reliably.

> You could also supply a test case that can be compiled and reproduced.
>
> To get a test case, add -v -save-temps to the compiler options and
> recompile.  Then post the console output of the compiler and the .ii file.

Here is the console output.  I'm attaching the .ii file and the .cpp
file used for the compilation.

    [227] jgeisler:~/classes/enp341 % avr-g++ -Wall -Os -ffunction-sections 
-fdata-sections -fno-exceptions -mmcu=atmega328p -DF_CPU=16000000UL -MMD -MP 
-MF"main.d" -MT"main.d" -c -o test.o test.cpp -v -save-temps
    Using built-in specs.
    COLLECT_GCC=/usr/x86_64-pc-linux-gnu/avr/gcc-bin/4.7.2/avr-g++
    Target: avr
    Configured with: 
/var/tmp/portage/cross-avr/gcc-4.7.2/work/gcc-4.7.2/configure --prefix=/usr 
--bindir=/usr/x86_64-pc-linux-gnu/avr/gcc-bin/4.7.2 
--includedir=/usr/lib/gcc/avr/4.7.2/include 
--datadir=/usr/share/gcc-data/avr/4.7.2 
--mandir=/usr/share/gcc-data/avr/4.7.2/man 
--infodir=/usr/share/gcc-data/avr/4.7.2/info 
--with-gxx-include-dir=/usr/lib/gcc/avr/4.7.2/include/g++-v4 
--host=x86_64-pc-linux-gnu --target=avr --build=x86_64-pc-linux-gnu 
--disable-altivec --disable-fixed-point --without-ppl --without-cloog 
--enable-lto --enable-nls --without-included-gettext --with-system-zlib 
--enable-obsolete --disable-werror --enable-secureplt --disable-multilib 
--disable-libmudflap --disable-libssp --disable-libgomp 
--with-python-dir=/share/gcc-data/avr/4.7.2/python 
--enable-poison-system-directories --enable-checking=release --disable-libgcj 
--disable-libquadmath --enable-languages=c,c++ --enable-shared 
--disable-threads --disable-bootstrap --with-bugurl=http://bugs.gentoo.org/ 
--with-pkgversion='Gentoo 4.7.2 p1.0, pie-0.5.3'
    Thread model: single
    gcc version 4.7.2 (Gentoo 4.7.2 p1.0, pie-0.5.3)
    COLLECT_GCC_OPTIONS='-Wall' '-Os' '-ffunction-sections' '-fdata-sections' 
'-fno-exceptions' '-mmcu=atmega328p' '-D' 'F_CPU=16000000UL' '-MMD' '-MP' '-MF' 
'main.d' '-MT' 'main.d' '-c' '-o' 'test.o' '-v' '-save-temps'
     /usr/libexec/gcc/avr/4.7.2/cc1plus -E -quiet -v -MMD test.d -MF main.d -MP 
-MT main.d -D F_CPU=16000000UL test.cpp -mmcu=atmega328p -Wall 
-ffunction-sections -fdata-sections -fno-exceptions -Os -fpch-preprocess 
-fno-rtti -fno-enforce-eh-specs -fno-exceptions -o test.ii
    ignoring nonexistent directory "/usr/lib/gcc/avr/4.7.2/include/g++-v4"
    ignoring nonexistent directory "/usr/lib/gcc/avr/4.7.2/include/g++-v4/avr"
    ignoring nonexistent directory 
"/usr/lib/gcc/avr/4.7.2/include/g++-v4/backward"
    ignoring nonexistent directory 
"/usr/lib/gcc/avr/4.7.2/../../../../avr/sys-include"
    #include "..." search starts here:
    #include <...> search starts here:
     /usr/lib/gcc/avr/4.7.2/include
     /usr/lib/gcc/avr/4.7.2/include-fixed
     /usr/lib/gcc/avr/4.7.2/../../../../avr/include
    End of search list.
    COLLECT_GCC_OPTIONS='-Wall' '-Os' '-ffunction-sections' '-fdata-sections' 
'-fno-exceptions' '-mmcu=atmega328p' '-D' 'F_CPU=16000000UL' '-MMD' '-MP' '-MF' 
'main.d' '-MT' 'main.d' '-c' '-o' 'test.o' '-v' '-save-temps'
     /usr/libexec/gcc/avr/4.7.2/cc1plus -fpreprocessed test.ii -quiet -dumpbase 
test.cpp -mmcu=atmega328p -auxbase-strip test.o -Os -Wall -version 
-ffunction-sections -fdata-sections -fno-exceptions -fno-rtti 
-fno-enforce-eh-specs -fno-exceptions -o test.s
    GNU C++ (Gentoo 4.7.2 p1.0, pie-0.5.3) version 4.7.2 (avr)
            compiled by GNU C version 4.5.4, GMP version 5.0.2, MPFR version 
3.0.1-p4, MPC version 0.8.2
    warning: MPFR header version 3.0.1-p4 differs from library version 3.1.1.
    GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
    GNU C++ (Gentoo 4.7.2 p1.0, pie-0.5.3) version 4.7.2 (avr)
            compiled by GNU C version 4.5.4, GMP version 5.0.2, MPFR version 
3.0.1-p4, MPC version 0.8.2
    warning: MPFR header version 3.0.1-p4 differs from library version 3.1.1.
    GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
    Compiler executable checksum: 5e7b521416cf40df37e35c64e8937dd8
    COLLECT_GCC_OPTIONS='-Wall' '-Os' '-ffunction-sections' '-fdata-sections' 
'-fno-exceptions' '-mmcu=atmega328p' '-D' 'F_CPU=16000000UL' '-MMD' '-MP' '-MF' 
'main.d' '-MT' 'main.d' '-c' '-o' 'test.o' '-v' '-save-temps'
     /usr/libexec/gcc/avr/as -mmcu=atmega328p -mno-skip-bug -o test.o test.s
    
COMPILER_PATH=/usr/libexec/gcc/avr/4.7.2/:/usr/libexec/gcc/avr/4.7.2/:/usr/libexec/gcc/avr/:/usr/lib/gcc/avr/4.7.2/:/usr/lib/gcc/avr/
    
LIBRARY_PATH=/usr/lib/gcc/avr/4.7.2/:/usr/lib/gcc/avr/4.7.2/../../../../avr/lib/
    COLLECT_GCC_OPTIONS='-Wall' '-Os' '-ffunction-sections' '-fdata-sections' 
'-fno-exceptions' '-mmcu=atmega328p' '-D' 'F_CPU=16000000UL' '-MMD' '-MP' '-MF' 
'main.d' '-MT' 'main.d' '-c' '-o' 'test.o' '-v' '-save-temps'
    [228] jgeisler:~/classes/enp341 %

                                                -- Jonathan Geisler --