gcc bug? (was bug in gen5200/tod/pcf8563.c)

Wolfram Wadepohl Wolfram.Wadepohl at ek-automation.com
Tue May 15 14:11:47 UTC 2007

Ingolf Steinbach schrieb:

> 2007/5/15, Wolfram Wadepohl <Wolfram.Wadepohl at ek-automation.com>:
>>              |    v1 = info[PCF8563_DAY_ADR-PCF8563_SECOND_ADR] &
>> PCF8563_DAY_MASK;
>>           175|    time->day = From_BCD(v1);
> How exactly is info declared. If it is meant to be a pointer to some
> hardware register, it should be volatile qualified (e.g. "uint32_t
> volatile* info").

     uint8_t         info[10];
     uint32_t         v1, v2;

info is filled by a function from the i2c bus

> If it is not qualified, an optimizing compiler might (IMO correctly)
> deduce that it is not necessary to place the value read from
> info[....] in the v1 variable if there is no function call between the
> assignment v1 = .... and the expanded From_BCD() macro. The compiler
> might decide that it is equivalent read the value at info[....] twice
> in the macro expansion thus leading to two different _x values.

Schöne Grüße aus Reutlingen

Wolfram Wadepohl
Forschung & Entwicklung

Indumat GmbH & Co. KG
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