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[avr-gcc-list] First steps with avr-gcc

From: David Bourgeois
Subject: [avr-gcc-list] First steps with avr-gcc
Date: Fri, 21 Oct 2005 20:00:01 +0200
User-agent: Opera M2/8.50 (Win32, build 7700)


I'm pretty new at avr-gcc and the GNU suite. I'm using WinAVR integrated with AVR Studio 4.12 (RC1).

Here's the simple function I'm using and the asm code generated (I should better do a macro out of it).

uint8_t getSwitches(void)
    return (PINB & SW_MK);

@00000074: getSwitches
24:       {
+00000074:   B183        IN      R24,0x03         In from I/O location
+00000075:   2799        CLR     R25              Clear Register
26:       }
+00000076: 718D ANDI R24,0x1D Logical AND with immediate +00000077: 7090 ANDI R25,0x00 Logical AND with immediate
+00000078:   9508        RET

avr-gcc -mmcu=atmega88 -Wall -gdwarf-2 -DF_CPU=8000000 -O2 -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums -Wp,-M,-MP,-MT,main.o,-MF,dep/main.o.d -c ../main.c -o main.o

My questions:
- The C code is not complete in the list file. Usually, the next line after a '{' is missing. Is there something wrong on my side or should it simply be like this? - the function uses 2 registers (16 bits) while it should only use 8 bits. Is there something wrong on the make settings I used (generated by AVR Studio btw) or something else? - I'm surely lacking some knowledge here, should I first start reading the make manual, the gcc one or simply improve my C knowledge?



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