Date: Sun, 15 Sep 2013 09:14:57 -0500 From: Nathan Whitehorn <nwhitehorn@freebsd.org> To: Eitan Adler <lists@eitanadler.com> Cc: Ian Lepore <ian@freebsd.org>, John-Mark Gurney <jmg@funkthat.com>, "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org>, freebsd-sparc64 <freebsd-sparc64@freebsd.org>, FreeBSD PowerPC ML <freebsd-ppc@freebsd.org> Subject: Re: Patch for Cross-Reference Phandles Message-ID: <5235C0E1.9080009@freebsd.org> In-Reply-To: <CAF6rxgmiYxEEBtK2Rt0-PoKfu8MP6gow%2B-Ncx7Ma3LFzGd8e9w@mail.gmail.com> References: <522CC7E0.9060508@freebsd.org> <5231D8A6.9080501@freebsd.org> <20130914133155.GA32845@alchemy.franken.de> <52346D71.4080407@freebsd.org> <1379173405.1197.7.camel@revolution.hippie.lan> <20130914172735.GX68682@funkthat.com> <1379181341.1197.26.camel@revolution.hippie.lan> <CAJ-Vmonk_cjc%2BwfCqsHdVESMvRMQTP4c2myK9jZr_%2B59GmWLQQ@mail.gmail.com> <CAF6rxgmiYxEEBtK2Rt0-PoKfu8MP6gow%2B-Ncx7Ma3LFzGd8e9w@mail.gmail.com>
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On 09/14/13 19:04, Eitan Adler wrote:
> [ *please* bottom post ]
>
> On Sat, Sep 14, 2013 at 7:56 PM, Adrian Chadd <adrian@freebsd.org> wrote:
>> ... holy crap. :-)
>>
>> erm, try writing some code that does something with it:
>>
>> int foo[2] = { 0, 0 };
>>
>> main()
>> {
>> int i;
>> for (i = 0; i < 2; i++) {
>> foo[i] = i;
>> }
>> }
>>
>> .. and then make foo[2] be foo[512] and explicitly set it up to be zero'ed.
>> see what happens.
> With an explicit zeroing:
>
> text data bss dec hex filename
> 1572 484 16 2072 818 a.out
>
> Without:
>
> text data bss dec hex filename
> 1572 484 16 2072 818 a.out
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There's an explanation of this behavior attached to the
-fno-zero-initialized-in-bss argument to GCC. I've pasted the relevant
section of the man page below:
-fno-zero-initialized-in-bss
If the target supports a BSS section, GCC by default puts
variables
that are initialized to zero into BSS. This can save space
in the
resulting code.
This option turns off this behavior because some programs
explic-
itly rely on variables going to the data section. E.g., so that
the resulting executable can find the beginning of that section
and/or make assumptions based on that.
The default is -fzero-initialized-in-bss.
This is why I wasn't worried about the = 0...
-Nathan
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