Arch Linux

Description:
The avr-gcc PKGBUILD was changed in 4.8.0-1 to add --enable-linker-build-id to the gcc configuration command line. Presumably this was copy-and-pasted from the PKGBUILD for normal (non-cross-compiling) gcc, where it doesn't affect anything. But when compiling for avr, the '.note.gnu.build-id' section gets dumped at address zero in compiled executables, meaning that the interrupt vector table is wrong. Which is bad. Very bad.

I filed a bug upstream (http://sourceware.org/bugzilla/show_bug.cgi?id=15389), requesting that the linker scripts in avr-binutils be updated to prevent this from happening, but strictly speaking, the 'right' solution is not to configure with --enable-linker-build-id; in fact, it's probably even better to explicitly use --disable-linker-build-id since enabling by default has been discussed (http://gcc.gnu.org/ml/gcc-patches/2010-10/msg00253.html) in the past, although it hasn't happened up to this point.


Additional info:
avr-gcc 4.7.2-1: works
avr-gcc 4.8.0-1: broken
avr-binutils 2.23.2-1: not directly implicated


Steps to reproduce:
1. install avr-gcc 4.8.0-1
2. compile any program for any target avr:
echo 'int main(void) {}' >broken.c
avr-gcc -mmcu=atmega324p -c broken.c
avr-gcc -mmcu=atmega324p -o broken.elf broken.o
3. run 'avr-objdump -h' and 'avr-objdump -D' on the executable
4. observe that .text begins at 0x24 (!)

5. roll back to 4.7.2-1, compile again, and note that the bad section is gone
6. with 4.7.2-1, explicitly use -Wl,--build-id when linking and it's back

7. compare the output of avr-gcc with the '-v' option at the linker step between the two versions, which clearly shows that the --build-id option is passed to the linker when using the 4.8.0-1 package, but not the 4.7.2-1 package