Re: [avr-gcc-list] GCC 6.1.0, strings and PROGMEM

[Senthil Kumar Selvaraj]

Senthil Kumar Selvaraj writes:

> Alan Burlison writes:
>
>> I've just updated my toolchain to use GCC 6.1.0 and I notice that
>> constant C strings seem to be being placed automatically in PROGMEM,
>> rather than requiring the use of the PSTR macro as in the past. This
>> caused me some confusion because call such as printf("foo") started
>> printing garbage. Here's the proof:
>>
>>         printf("          ");
>>      91e:       84 e7           ldi     r24, 0x74       ; 116
>>      920:       90 e0           ldi     r25, 0x00       ; 0
>>      922:       9f 93           push    r25
>>      924:       8f 93           push    r24
>>      926:       0e 94 04 17     call    0x2e08  ; 0x2e08 <printf>
>>
>>       74:       20 20           and     r2, r0
>>       76:       20 20           and     r2, r0
>>       78:       20 20           and     r2, r0
>>       7a:       20 20           and     r2, r0
>>       7c:       20 20           and     r2, r0
>>       7e:       00 21           and     r16, r0
>>
>> I haven't been able to find any mention of this change anywhere. Is
>> this a deliberate change in gcc behaviour, or a bug?
>
> It looks correct to me. From the dissassembly output, I guess you're
> looking at contents at 0x0074 in the flash address space. You should
> be looking at contents in the data address space instead. Can you try
> dumping contents of the .data section, like so (assuming a.out is the ELF 
> output)
>
> $ avr-objdump -s -j .data a.out
>
> You should see the blank space string at 0x0074 in the output.
>
> Don't know why you're getting garbage output though. Can you post a
> testcase that shows the incorrect behavior?
>

Filed https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71151 to track this.

Regards
Senthil