Re: [Iverilog-devel] preprocessor abuse?

[Stephen W. <st...@ic...>]

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Mixed feelings here about the use of macros. My gripe is that
they often make opaque what's going on. I think the example below
is not something I would reject as it doesn't suffer that ill.

I add though that I prefer macros over ifdef's and templates
and/or inline functions over macros, although functions/templates
don't work sometimes where macros are usefully used.

Larry Doolittle wrote:
> Guys -
> 
> I'm often tempted to produce patches like the one appended.
> I don't know how hostile the reaction will be.  If you don't
> like it, just say so.
> 
> The advantages include compactness, ease of extension, and
> intrinsic self-consistency.  It might also be considered more
> opaque and harder to debug, but there are lots of things like
> that buried in Icarus, so maybe it doesn't matter.  :-p
> 
> This patch doesn't affect the size of the object code.
> That can be accomplished with a loop and a data structure,
> where the data structure itself uses some preprocessor work.
> Untested concept:
> 
> struct {bool *flag, const char *name} debug_entry;
> struct debug_entry debug_flag_table[]={
> #define ENTRY(x) { &debug_##x, #x}
> 	ENTRY(scopes),
> 	ENTRY(eval_tree),
> 	ENTRY(elaborate),
> 	ENTRY(synth2)
> #undef ENTRY
> };
> 
>    - Larry
> 
> --- verilog/main.cc	2008-02-06 15:19:07.000000000 -0800
> +++ /home/ldoolitt/src/verilog-0.9/main.cc	2008-02-06 15:42:15.000000000 -0800
> @@ -356,20 +356,14 @@
>  		  basedir = strdup(cp);
>  
>  	    } else if (strcmp(buf, "debug") == 0) {
> -		  if (strcmp(cp, "scopes") == 0) {
> -			debug_scopes = true;
> -			cerr << "debug: Enable scopes debug" << endl;
> -		  } else if (strcmp(cp,"eval_tree") == 0) {
> -			debug_eval_tree = true;
> -			cerr << "debug: Enable eval_tree debug" << endl;
> -		  } else if (strcmp(cp,"elaborate") == 0) {
> -			debug_elaborate = true;
> -			cerr << "debug: Enable elaborate debug" << endl;
> -		  } else if (strcmp(cp,"synth2") == 0) {
> -			debug_synth2 = true;
> -			cerr << "debug: Enable synth2 debug" << endl;
> -		  } else {
> -		  }
> +#define DEBUG_FLAG(x) (strcmp(cp, #x) == 0) {debug_##x = true; \
> +	cerr << "debug: Enable " #x " debug" << endl;}
> +		       if DEBUG_FLAG(scopes)
> +		  else if DEBUG_FLAG(eval_tree)
> +		  else if DEBUG_FLAG(elaborate)
> +		  else if DEBUG_FLAG(synth2)
> +		  else { }
> +#undef DEBUG_FLAG
>  
>  	    } else if (strcmp(buf, "depfile") == 0) {
>  		  depfile_name = strdup(cp);
> 
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- --
Steve Williams                "The woods are lovely, dark and deep.
steve at icarus.com           But I have promises to keep,
http://www.icarus.com         and lines to code before I sleep,
http://www.picturel.com       And lines to code before I sleep."
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