Volatile Keyword

Anish Mathew

TI Compiler Experts,

I am using a global "volatile" variable which is not referenced in any functions or anywhere in my program. After I compile the program with C6000 compiler, the map file generated contains no mention of the global variable. But when I add line of dummy code to make use of the volatile variable inside a function, after compilation I am able to find the variable in global symbol section of the map file.

My question is why is compiler ignoring volatile keyword used with variable declaration?

Thanks

Anish

Signalogic

over 11 years ago

0 Johannes over 11 years ago

Mastermind 6240 points

Hi,

I believe that because the variable was not being used anywhere, the compiler optimized it out, even if it was declared as volatile. When you use it, it doesn't optimize it because it knows that the variable is being changed somewhere (indicated by volatile keyword).

Regards

0 George Mock over 11 years ago in reply to Johannes

TI__Guru**** 251820 points

The response by Johannes is correct. The standard says the compiler may not optimize away a volatile memory read or write. The standard is silent about whether the compiler may optimize away a volatile variable which never performs any reads or writes.

Thanks and regards,

-George

0 Anish Mathew over 11 years ago in reply to George Mock

Intellectual 395 points

Thanks George and Johannes.

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Volatile Keyword