Compiler issue

Hello,

the simple line

while(i0.NewDataFromEeprom == FALSE);

is compiled differently by CrossStudio for ARM.

For ARM Ram Debug the compilation is correct:

A0003448 E59F3064 ldr r3, 0xA00034B4 <MainInit2+0x19c>

A000344C E5933034 ldr r3, [r3, #0x34]

A0003450 E3530000 cmp r3, #0

A0003454 0AFFFFFB beq 0xA0003448 <MainInit2+0x130>

But for ARM Flash Debug the result is

00004178 E59F30A0 ldr r3, 0x00004220 <MainInit2+0x1e8>

0000417c E5933034 ldr r3, [r3, #0x34]

00004180 E3530000 cmp r3, #0

00004184 0A00001E beq 0x00004204 <MainInit2+0x1cc>

...

00004204 EAFFFFFE b 0x00004204 <MainInit2+0x1cc>

...

I.e. it becomes an infinite loop without checking the variable any longer.

The first idea was that a project property setting might be wrong. But the suspicious ones are equal in both configurations:

Enable Unused Symbol Removal No

Optimization Level None

Keep symbols _vectors

What might be the reason for these different results?

Does anybody have clue?

Regards,

Henry

Paul Curtis

July 04, 2011 11:07

Obviously (or not so obviously) the compiler understands that i0.NewDataFromEeprom

July 04, 2011 13:14

Hello Paul,

could you go into more details, please?

Why is i0.NewDataFromEeprom not checked any longer?

What is my mistake?

July 04, 2011 13:16

Your mistake is you did not use volatile. Please go and read a good book on C to understand volatile correctly.

July 04, 2011 14:43

I did not expect that volatile would make any difference in the same project, meaning that it is ok. with the RAM configuration but not with the FLASH configuration. Anyway, that solved the problem

Thanks for your help!

Compiler issue

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