[Bug c/44928] New: volatile globals illegally ignored on optimization levels >0

[asche at primion dot de]

Hi there, the ARM compiler (we use 4.4.1 but could also verify this on
different platforms) illegally ignores the volatile statement on globals when
optimization >0 is used. Here is an example:

volatile unsigned char *glbDummyToTestVolatileBug;

...

<somewhere in a function body>:

for (glbDummyToTestVolatileBug=0;glbDummyToTestVolatileBug<(unsigned char
*)100;)
{
    *glbDummyToTestVolatileBug++ = 0;
}

The generated assembly code will store the iteration in a register, not the
volatile global. Optimization level 0 will process this correctly.

Relevant compiler options being used are as follows:

-mthumb -mcpu=cortex-m3 -std=gnu99 -O3 -c -g  -pedantic -Wall -Wextra
-fshort-enums  

of course, the above code snippet is bogus, but is an abbreviated form of
something we rely on in our embedded controller.

Thanks!


-- 
           Summary: volatile globals illegally ignored on optimization
                    levels >0
           Product: gcc
           Version: 4.4.1
            Status: UNCONFIRMED
          Severity: critical
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: asche at primion dot de
 GCC build triplet: unknown
  GCC host triplet: unknown (PC host not running cygwin)
GCC target triplet: arm-none-eabi


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44928