[avr-gcc-list] avr-objdump behaviour

[Ben Mann]

Hi,

I have an AVR project which I would like to optimise a little (a lot) and
for this purpose I hoped to use the avr-objdump output.

Sorry for the length of the message, but I've tried to be brief :S

For some functions avr-objdump places source code lines in the .lst file,
while for others it does not... I can't seem to find documentation (or a
discussion with solution) about this behaviour, however I have a simple demo
below which will reproduce this feature for one apparent 'cause'. Note that
the source code lines (-l) are still clearly referenced, just not included.

Using the following command line,
-----------------------
        avr-gcc -g -Os -mmcu=atmega64 -c demo.c
        avr-objdump -h -S -l demo.c > demo.lst
-----------------------
compiling this .C file:
-----------------------
        void bar();

        void foo() {
            bar();
        }

        void bar() {
            unsigned char c;
            for(c = 255; c != 0; c--)
                ;
        }
-----------------------
Yields .lst file without the source line "bar();" (demo.c:4)
-----------------------
        ...snip!...
        00000000 <bar>:
        bar():
        .../demo.c:9
        }

        void bar() {
            unsigned char c;
            for(c = 255; c != 0; c--)
           0:   8f ef           ldi     r24, 0xFF       ; 255
           2:   81 50           subi    r24, 0x01       ; 1
           4:   f1 f7           brne    .-4             ; 0x2
           6:   08 95           ret

        00000008 <foo>:
        foo():
        .../demo.c:4
           8:   0e 94 00 00     call    0x0
           c:   08 95           ret
-----------------------
The problem (in this case) seems to be "resolved" by using -O0, however for
my larger project this doesn't seem to help (source lines missing for some
functions even *with* -O0).

Also, if the .C file is modified to remove the predeclaration:
-----------------------
        void bar() {
            unsigned char c;
            for(c = 255; c != 0; c--)
                ;
        }

        void foo() {
            bar();
        }
-----------------------
The output is suitable:
-----------------------
        ...snip!...
        00000000 <bar>:
        bar():
        .../demo2.c:3
        void bar() {
            unsigned char c;
            for(c = 255; c != 0; c--)
           0:   8f ef           ldi     r24, 0xFF       ; 255
           2:   81 50           subi    r24, 0x01       ; 1
           4:   f1 f7           brne    .-4             ; 0x2
           6:   08 95           ret

        00000008 <foo>:
        foo():
        .../demo2.c:8
                ;
        }

        void foo() {
            bar();
           8:   0e 94 00 00     call    0x0
           c:   08 95           ret
-----------------------
For a "big" project with interrupt vectors etc this behaviour seems too make
the -S option too complex to use. 

Is this sort of behaviour normal? I recall a discussion on this topic in the
list however I didn't find any solution in that case.

Regards

Ben Mann

PS  The WinAVR release is 20040720 on Windows.