RE: Large executables

[David Korn <dkorn at pixelpower dot com>]

>-----Original Message-----
>From: Steve deRosier [mailto:sderosier@vari-lite.com]
>Sent: 30 January 2001 18:09

>I am having problems with using optimizations on my xgcc. Without using any
>optimizations, my final srec files are over twice as large as I used to get
>from the same code compiled with the MRI tools.

  For gcc, -O0 means *really* no optimisations, including some things that
other compilers do by default, such as constant folding...

>  The problem is, the instant
>I turn on any optimizations (at any level of -O, no mater -O1 
>through -O3,
>-Os also breaks), my code no longer runs properly.  Been playing with
>various options but I can't seem to come up with anything that works.

  Well, your code has bugs which are being exposed by the optimizer.  One
of the most common causes of bugs (I notice you work in embedded s/w) that
appear the moment the optimizer is turned on is not using 'volatile'
properly on things that need it.  Other problems that often don't make
themselves noticeable until the optimizer is turned on are use of 
uninitialized variables, and some buffer overflows.  Apart from that I 
can't offer any terribly specific advice; if this doesn't help, post back
to the list with a more detailed description of what target you're using
and precisely what problems appear when you switch on the optimizer.
  

    good luck, 
        DaveK
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