Hello, I have been working on a project for some time and at some point, everything just stopped working. It appears that as soon as I include an ISR in my C code, the main function won't even be called anymore. I reduced my code to this:
#include <avr/io.h> #include <avr/interrupt.h> int main (void) { cli(); DDRB = 0xff; while(1) PORTB |= (1 << PB5); return 0; } ISR(TIMER0_OVF_vect) {} But the LED just won't turn on. The strange thing is: If I remove the ISR at the bottom without changing anything else, even keeping the include, everything works. If I remove the -Os option from gcc but keep the ISR, everything works. I use these commands to compile, link and flash it: F_CPU=16000000L avr-gcc -Wall -DF_CPU=$F_CPU -c -mmcu=atmega168 -Os main.c -o main.o avr-ld -mavr5 -o led-test.elf main.o avr-objcopy -O ihex led-test.elf led-test.hex sudo avrdude -c avrisp2 -p atmega168 -P usb -b 57600 -U flash:w:led-test.hex I am quite new to the avr tools so I might just have made a silly mistake, so I would appreciate any tips! Thank you! LSB: Distributor ID: Ubuntu Description: Ubuntu 16.04 LTS Release: 16.04 Codename: xenial Output of avr-gcc -v: Using built-in specs. Reading specs from /usr/lib/gcc/avr/4.9.2/device-specs/specs-avr2 COLLECT_GCC=avr-gcc COLLECT_LTO_WRAPPER=/usr/lib/gcc/avr/4.9.2/lto-wrapper Target: avr Configured with: ../src/configure -v --enable-languages=c,c++ --prefix=/usr/lib --infodir=/usr/share/info --mandir=/usr/share/man --bindir=/usr/bin --libexecdir=/usr/lib --libdir=/usr/lib --enable-shared --with-system-zlib --enable-long-long --enable-nls --without-included-gettext --disable-libssp --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=avr CFLAGS='-g -O2 -fstack-protector-strong -Wformat ' CPPFLAGS=-D_FORTIFY_SOURCE=2 CXXFLAGS='-g -O2 -fstack-protector-strong -Wformat ' FCFLAGS='-g -O2 -fstack-protector-strong' FFLAGS='-g -O2 -fstack-protector-strong' GCJFLAGS='-g -O2 -fstack-protector-strong' LDFLAGS='-Wl,-Bsymbolic-functions -Wl,-z,relro' OBJCFLAGS='-g -O2 -fstack-protector-strong -Wformat ' OBJCXXFLAGS='-g -O2 -fstack-protector-strong -Wformat ' Thread model: single gcc version 4.9.2 (GCC)
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