GCC optimisations / assembler error?

Follow

Glen English

• October 18, 2012 02:19

Hi , can someone please point me to a forum where I can ask a GCC compiled code question (if this is the wrong one).

********

I'm new to GCC but have good long assembler experience on other micros (30 years).

I think the compiler is doing something wrong, but, well I could have done something wrong. But I don't think so.

I have the code segment OPT LEVEL1 and NO OPTIMISATION  and wanted an opinion.

The code puts itself into an endless loop, as verified in the debugger. I attached my predicament if anyone is interested.

regards. 

GCC1.pdf

0

• 

  VEIT Electronics - Martin Dušek

  • October 18, 2012 08:47

  Hi!

  I don't see anything strange about the examples you attached.

  When optimizing, the compiler assumes, that there is nothing inside while loop that can change the value of SymbolTimingBit, so it produces infinite loop.

  Declare SymbolTimingBit variable as "volatile".

  0

  Comment actions Permalink
• 

  Glen English

  • October 18, 2012 08:55

  Hi Martin 

  Thanks for looking. Much appreciated. It IS declared as volatile...... strange huh ?
  I do like your explanation. Makes sense.  
  OK  so it is declared as volatile. But. I smell a rat....
  Yes in my globals.c I have it as

  volatile bool SymbolTimingBit;

  but in my globals.h

  extern volatile bool SymbolTimingBit;

   

  That was it. Nice one Martin. cheers

   

  0

  Comment actions Permalink
• 

  Glen English

  • October 18, 2012 08:56

  but in my globals.h

  extern bool SymbolTimingBit;

   

  not volatile storage modifier. woops!

  0

  Comment actions Permalink

Please sign in to leave a comment.