Issue OPTIMIZE-DEBUG-INFO Writeup

Issue:		OPTIMIZE-DEBUG-INFO

References:	CLtL p. 160

Category:	ADDITION

Edit History:   V1  9 Sep 1988, David Gray (initial version)

                V2 19 Sep 1988, David Gray (delete first alternative)

 

Problem Description:


  The OPTIMIZE declaration provides a way to tell the compiler how important

  various qualities are in order to guide which optimizations are done.

  There is another quality, however, that is not mentioned, but is an

  important consideration for the compiler:  how much information

  should be included in the object code to facilitate debugging.  This

  includes both annotation added to enable a debugger to display more

  information to the user, and also suppression of optimizations that would

  confuse debugging by making it harder to connect the object code with the

  source code.


Proposal OPTIMIZE-DEBUG-INFO:NEW-QUALITY:


  In the description of the OPTIMIZE declaration, add an additional quality

  named DEBUG, described as "ease of debugging".

 

 Rationale:


  Since ease of debugging is an issue that the user will be concerned with,

  and is an issue that the compiler needs to consider, this provides a clear

  way for the user to control the amount of debugging information placed in

  the object module, with DEBUG=0 meaning none and DEBUG=3 meaning "as much

  as possible".

 

 Current Practice:


  No current implementation of this is known.

 

 Cost to implementors:


  All would have to update their handling of OPTIMIZE declarations to accept

  the new quality.

 

 Cost to users:


  One more little feature to learn.  Some problems may result from the

  addition of the symbol DEBUG to the LISP package.

  

 Benefits:


  Provides users a standard way to control the interaction between

  the compiler and debugger, and saves implementors from having to invent

  implementation-dependent solutions.


 Costs of Non-Adoption: 


  Continued confusion about how debug information should be controlled.

 

Discussion:


  Concern has been raised that there is already a problem with the

  non-orthogonality of SPEED, SAFETY, and SPACE that would be made even

  worse with DEBUG added, since users tend to be perplexed by the

  interactions of these qualities.