------- Comment #3 from martin at kfib dot org 2008-06-11 21:13 -------
Exact line for compiling is:
avr-gcc -mmcu=atmega48 -Wall test.c -o test
And now I'm very confused. I KNOW I've tried with and without optimization
before and that it made no difference (or possibly I'm a major clutz) but now I
can only reproduce the bug if I don't optimize. If I optimize (all kinds), I
get 3, but without optimization I get 2. This is what I get without
optimization:
6c: df 93 push r29
6e: cf 93 push r28
70: 00 d0 rcall .+0 ; 0x72 <main+0x6>
72: 00 d0 rcall .+0 ; 0x74 <main+0x8>
74: 00 d0 rcall .+0 ; 0x76 <main+0xa>
76: cd b7 in r28, 0x3d ; 61
78: de b7 in r29, 0x3e ; 62
7a: 80 91 00 01 lds r24, 0x0100
7e: 90 91 01 01 lds r25, 0x0101
82: 9c 83 std Y+4, r25 ; 0x04
84: 8b 83 std Y+3, r24 ; 0x03
86: 8a e3 ldi r24, 0x3A ; 58
88: 8d 83 std Y+5, r24 ; 0x05
8a: 1e 82 std Y+6, r1 ; 0x06
8c: 1a 82 std Y+2, r1 ; 0x02
8e: 19 82 std Y+1, r1 ; 0x01
90: 8b 81 ldd r24, Y+3 ; 0x03
92: 8a 33 cpi r24, 0x3A ; 58
94: 29 f4 brne .+10 ; 0xa0 <main+0x34>
96: 89 81 ldd r24, Y+1 ; 0x01
98: 9a 81 ldd r25, Y+2 ; 0x02
9a: 81 60 ori r24, 0x01 ; 1
9c: 9a 83 std Y+2, r25 ; 0x02
9e: 89 83 std Y+1, r24 ; 0x01
a0: 8d 81 ldd r24, Y+5 ; 0x05
a2: 8a 33 cpi r24, 0x3A ; 58
a4: 29 f4 brne .+10 ; 0xb0 <main+0x44>
a6: 89 81 ldd r24, Y+1 ; 0x01
a8: 9a 81 ldd r25, Y+2 ; 0x02
aa: 82 60 ori r24, 0x02 ; 2
ac: 9a 83 std Y+2, r25 ; 0x02
ae: 89 83 std Y+1, r24 ; 0x01
b0: e7 e2 ldi r30, 0x27 ; 39
b2: f0 e0 ldi r31, 0x00 ; 0
b4: 8f e0 ldi r24, 0x0F ; 15
b6: 80 83 st Z, r24
b8: e8 e2 ldi r30, 0x28 ; 40
ba: f0 e0 ldi r31, 0x00 ; 0
bc: 89 81 ldd r24, Y+1 ; 0x01
be: 80 83 st Z, r24
c0: 80 e0 ldi r24, 0x00 ; 0
c2: 90 e0 ldi r25, 0x00 ; 0
c4: 26 96 adiw r28, 0x06 ; 6
c6: 0f b6 in r0, 0x3f ; 63
c8: f8 94 cli
ca: de bf out 0x3e, r29 ; 62
cc: 0f be out 0x3f, r0 ; 63
ce: cd bf out 0x3d, r28 ; 61
d0: cf 91 pop r28
d2: df 91 pop r29
d4: 08 95 ret
The result is that my LEDs indicate a very shining 0x02 on the outport.
However, with -Os I get:
6c: 8f e0 ldi r24, 0x0F ; 15
6e: 87 b9 out 0x07, r24 ; 7
70: 83 e0 ldi r24, 0x03 ; 3
72: 90 e0 ldi r25, 0x00 ; 0
74: 88 b9 out 0x08, r24 ; 8
76: 80 e0 ldi r24, 0x00 ; 0
78: 90 e0 ldi r25, 0x00 ; 0
7a: 08 95 ret
This is with version 4.3.1. I've verified with 4.1.2 and it behaves the same;
without optimization it bugs, with it works. I guess I forgot to do a make
clean and thus deserve the title klutz. Sorry for the confusion.
Unfortunately the same doesn't go for my actual program (this one was just a
test case). It bugs badly no matter optimization (yes, I've verified that I've
made a make clean this time) and it boils down to that if I do:
display.write_string ("Hello");
it bugs, but if I do:
char h[6];
h[0] = 'H';
h[1] = 'e';
h[2] = 'l';
h[3] = 'l';
h[4] = 'o';
h[5] = 0;
display.write_string (h);
it prints out a nice little Hello on my LCD.
Something is definitely very fishy in how the char-arrays are handled and I
can't figure it out.
I know you said in the faq that you don't want the source code, but if you want
to look at it it's at http://martin.kfib.org/atmelLCD.zip. Maybe it can shed
some light over this.
It behave the same if I optimize or not (and I hope that I haven't screwed
anything up now...); in test.cc if I use the code that I claim works I get a
nice little Hello on the LCD but if I use the one that I clam doesn't work I
just get garbage on the LCD.
Would you like me to generate .i-files too or what's the next step?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36494
