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<H2>Issue OPTIMIZE-DEBUG-INFO Writeup</H2>
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<PRE><B>Issue:</B> <A HREF="iss251.htm">OPTIMIZE-DEBUG-INFO</A><P>
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<B>References:</B> CLtL p. 160<P>
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<B>Category:</B> ADDITION<P>
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<B>Edit History:</B> V1 9 Sep 1988, David Gray (initial version)<P>
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V2 19 Sep 1988, David Gray (delete first alternative)<P>
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<P>
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<B>Problem Description:<P>
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</B><P>
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The <A REL=DEFINITION HREF="../Body/d_optimi.htm#optimize"><B>OPTIMIZE</B></A> declaration provides a way to tell the compiler how important<P>
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various qualities are in order to guide which optimizations are done.<P>
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There is another quality, however, that is not mentioned, but is an<P>
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important consideration for the compiler: how much information<P>
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should be included in the object code to facilitate debugging. This<P>
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includes both annotation added to enable a debugger to display more<P>
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information to the user, and also suppression of optimizations that would<P>
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confuse debugging by making it harder to connect the object code with the<P>
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source code.<P>
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<P>
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<B>Proposal OPTIMIZE-DEBUG-INFO:NEW-QUALITY:<P>
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</B><P>
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In the description of the <A REL=DEFINITION HREF="../Body/d_optimi.htm#optimize"><B>OPTIMIZE</B></A> declaration, add an additional quality<P>
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named <A REL=DEFINITION HREF="../Body/d_optimi.htm#debug"><B>DEBUG</B></A>, described as "ease of debugging".<P>
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<P>
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Rationale:<P>
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<P>
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Since ease of debugging is an issue that the user will be concerned with,<P>
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and is an issue that the compiler needs to consider, this provides a clear<P>
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way for the user to control the amount of debugging information placed in<P>
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the object module, with DEBUG=0 meaning none and DEBUG=3 meaning "as much<P>
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as possible".<P>
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<P>
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Current Practice:<P>
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<P>
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No current implementation of this is known.<P>
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<P>
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Cost to implementors:<P>
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<P>
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All would have to update their handling of <A REL=DEFINITION HREF="../Body/d_optimi.htm#optimize"><B>OPTIMIZE</B></A> declarations to accept<P>
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the new quality.<P>
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<P>
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Cost to users:<P>
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<P>
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One more little feature to learn. Some problems may result from the<P>
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addition of the symbol <A REL=DEFINITION HREF="../Body/d_optimi.htm#debug"><B>DEBUG</B></A> to the LISP package.<P>
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<P>
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Benefits:<P>
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<P>
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Provides users a <A REL=DEFINITION HREF="../Body/07_ffb.htm#standard"><B>standard</B></A> way to control the interaction between<P>
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the compiler and debugger, and saves implementors from having to invent<P>
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implementation-dependent solutions.<P>
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<P>
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Costs of Non-Adoption: <P>
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<P>
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Continued confusion about how debug information should be controlled.<P>
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<P>
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<B>Discussion:<P>
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</B><P>
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Concern has been raised that there is already a problem with the<P>
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non-orthogonality of <A REL=DEFINITION HREF="../Body/d_optimi.htm#speed"><B>SPEED</B></A>, <A REL=DEFINITION HREF="../Body/d_optimi.htm#safety"><B>SAFETY</B></A>, and <A REL=DEFINITION HREF="../Body/d_optimi.htm#space"><B>SPACE</B></A> that would be made even<P>
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worse with <A REL=DEFINITION HREF="../Body/d_optimi.htm#debug"><B>DEBUG</B></A> added, since users tend to be perplexed by the<P>
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interactions of these qualities. <P>
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</PRE>
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