Optimizing while(1);

[unified]

Hi

Looking for opinions on whether an optimizer could remove

while(1) {};

This is often used in embedded systems when it is desired to "commit
suicide" by waiting for a watchdog reset.

Thanks
Colin

 

[Andrew Poelstra]

Hi

Looking for opinions on whether an optimizer could remove

while(1) {};

This is often used in embedded systems when it is desired to "commit
suicide" by waiting for a watchdog reset.

Nope. Optimizers are not allowed to change the effect of code,
and an infinite loop is certainly not a no-op.

 

[Nick Keighley]

Looking for opinions on whether an optimizer could remove

while(1) {};

This is often used in embedded systems when it is desired to "commit
suicide" by waiting for a watchdog reset.

yes.

 

[Richard Bos]

yes.

No. Removing that line would change the semantics of the code (rather
drastically), so that's not allowed.
Of course, an optimiser still _could_ remove that line, just as an
optimiser _could_ remove all printf() calls in your program. But neither
would be a very good optimiser.

Richard

 

[Ian Collins]

Hi

Please don't multi-post on Usenet. Answered elsewhere as well as here...

 

[MisterE]

Hi

Looking for opinions on whether an optimizer could remove

while(1) {};

This is often used in embedded systems when it is desired to "commit
suicide" by waiting for a watchdog reset.

Some compilers will appear to have removed while(1); if its the only
thing before the end of main. This is because if you go to the full
listing of your program you will typically find after main returns that
compilers on embedded systems will then go into there own while(1) loop.
Check your program output listing.

 

[Tim Rentsch]

Nope. Optimizers are not allowed to change the effect of code,
and an infinite loop is certainly not a no-op.

The question is whether the Standard allows it; there
are arguments both pro and con.