debug = x overrides command line

[Steven Schveighoffer via Digitalmars-d]

On 10/22/14 4:15 PM, Walter Bright wrote:
> On 10/22/2014 1:04 PM, Jonathan M Davis wrote:
>> Yeah, being able to just enable the debug blocks from within the code
>> like
>> that seems questionable to me and has nothing to do with debug blocks
>> disabling pure functions. It just makes for a nastier side effect when
>> debug
>> blocks are enabled within the code rather than via the command-line.
>
> Lots of people (like me, though I'm often told I'm a unique snowflake
> and nobody programs like me) debug code by editting the source code to
> enable/disable debug code rather than messing with the makefile.

This is a good point. Enabling debug on a specific feature/module in a 
complex build system is not easy. For someone simply typing dmd *.d, 
this is trivial, but not if you have to go edit a makefile, or try to 
figure out how to pass arguments to it (I need to look that up every time).

>
> Take a look at about any source file in dmd, for example, with the
> commented out printf's, and template.c, with the file scope #define LOG 0.
>
> D needs to support this style of debugging, and the 'debug' conditional
> with how it is set is just the ticket. The feature works as designed and
> intended.

I think there is a problem though. What if you leave your debug in by 
accident? Now your pure code isn't so pure, and you have no idea.

As we all know from "const-by-convention" C++, if there is an easy way 
to "get around" something that the compiler makes difficult, people will 
exploit it. I would hate to see someone using this "feature" to simply 
make something impure pure so they can get it to compile.

I propose a compromise. By default, the compiler emits warnings when 
debug=x is executed, AS LONG AS it's not inside a debug block already 
enabled by a command line debug directive. However, if the compiler has 
any of the following switches, then then warnings are suppressed:

-unittest
-g
-gc
-debug

The theory being, you are testing the code with these switches, not 
releasing it. This way, you can add your debug=x enablers when doing 
make debug or make unittest, but once you go to make release, you get 
the warning.

Optionally, we could have a dedicated switch to suppress these warnings.

Does this sound reasonable?

-Steve