[phobos] large object files and binaries

[Walter Bright]

On 5/3/2011 10:30 AM, Steve Schveighoffer wrote:
> This is not a fair response to this problem.  When the code size triples 
> (http://d.puremagic.com/issues/show_bug.cgi?id=2254) because you add the -lib 
> switch, and adding unit tests adds to the size of the executable, even when 
> unit tests are turned off (http://d.puremagic.com/issues/show_bug.cgi?id=5560) 
> again, when adding the -lib switch, it's obvious to everyone (but you it 
> seems) that the -lib switch is adding bloat.  Bug 5660 proves that beyond all 
> reasonable doubt.

Again, this is simply not relevant information. Each obj file has bookkeeping 
overhead required by the ELF file format. By looking at the object file size, 
you have ZERO information about the size of code/data making it into the executable.

>
> Whether it accounts for all the added bloat, I'm not sure.  obj2asm is a great 
> tool, but I am not an assembly developer, I can't always decipher what's going on.

You do not need to know a single iota of assembler to understand where size is 
coming from in the output of obj2asm.

>   the -map switch only tells you what the compiler is outputting,

No, it doesn't. It tells you what symbols (i.e. functions) made it into the 
executable, and the size contributed by each function.

> it doesn't tell you if the output contains unnecessary bloat.

It does if the functions in the executable don't need to be there.

>
> Please, at least agree to look at bug 5560, it's irrefutable proof that the 
> -lib switch adds bloat, it cannot get any simpler than that.

I'm afraid 5560 doesn't prove that. Without looking at the obj2asm contents of 
those .o files, you simply cannot conclude there is any bloat in there or if it 
is nothing more than the ELF bookkeeping.

>
> -Steve
>
>     --------------------------------------------------------------------------------
>     *From:* Walter Bright <walter at digitalmars.com>
>     *To:* Steve Schveighoffer <schveiguy at yahoo.com>; Discuss the phobos
>     library for D <phobos at puremagic.com>
>     *Sent:* Tuesday, May 3, 2011 12:57 PM
>     *Subject:* large object files and binaries
>
>
>
>     On 5/3/2011 7:39 AM, Steve Schveighoffer wrote:
>>     Dmd has steadily been making binaries more bloated for the last couple
>>     years (many times pointed out in the NG and there are several bugzilla
>>     reports).
>
>     There are two causes of this:
>
>     1. Typeinfo getting larger, and people wanting more features in Typeinfo
>     (like precise gc) so this will continue to increase.
>
>     2. Every phobos module imports and relies on every other one.
>
>
>     To find out why .o files are large, run obj2asm on it. To find out why
>     executables are large, compile with the -map switch and examine the linker
>     .map file. <rant>AFAIK, I'm the only person who ever does this.</rant>
>
>     Please, everyone. Once in a while, run obj2asm on the library module
>     you're developing and have a look-see at what is coming out of the compiler.
>
>
>
>
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