Date: Sat, 14 Apr 2012 14:56:51 -0400
From: Christopher Faylor <cgf-use-the-mailinglist-please AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: gcc: turning off large-address awareness
Message-ID: <20120414185651.GB17287@ednor.casa.cgf.cx>
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On Sat, Apr 14, 2012 at 01:52:46PM -0400, Earnie Boyd wrote:
>On Sat, Apr 14, 2012 at 1:33 PM, Christopher Faylor wrote:
>> On Sat, Apr 14, 2012 at 01:21:25PM -0400, Ken Brown wrote:
>>>On 4/14/2012 12:37 PM, Earnie Boyd wrote:
>>>> On Sat, Apr 14, 2012 at 7:52 AM, Ken Brown wrote:
>>>>> For testing purposes, I'd like to build without large-address awareness.
>>>>> ?? What's the right way to do that? ??I tried
>>>>>
>>>>> ?? ??LDFLAGS=-Wl,--no-large-address-aware
>>>>>
>>>>> and
>>>>>
>>>>> ?? ??LDFLAGS=-Wl,--disable-large-address-aware
>>>>>
>>>>> but both resulted in "unrecognized option" errors from ld.
>>>>
>>>> You specify --large-address-aware if you want it and don't specify if
>>>> you don't want it.
>>>
>>>Sorry, I should have explained more clearly what the issue is. ??Cygwin's
>>>gcc specifies --large-address-aware by default:
>>>
>>>$ gcc -dumpspecs | grep large
>>> ?? %{mwindows:--subsystem windows} ?? %{mconsole:--subsystem console}
>>>%{!mno-cygwin:%{!mno-use-libstdc-wrappers: ?? --wrap _Znwj ?? --wrap _Znaj
>>> ?? --wrap _ZdlPv ?? --wrap _ZdaPv ?? --wrap _ZnwjRKSt9nothrow_t ?? --wrap
>>>_ZnajRKSt9nothrow_t ?? --wrap _ZdlPvRKSt9nothrow_t ?? --wrap
>>>_ZdaPvRKSt9nothrow_t }} ?? %{shared: %{mdll: %eshared and mdll are not
>>>compatible}} ?? %{shared: --shared} %{mdll:--dll} ?? %{static:-Bstatic}
>>>%{!static:-Bdynamic} ?? %{shared|mdll: --enable-auto-image-base -e
>>>%{mno-cygwin:_DllMainCRTStartup AT 12}
>>>%{!mno-cygwin:__cygwin_dll_entry AT 12}}
>>>%{!mno-cygwin:--dll-search-prefix=cyg ?? ?? %{!shared: %{!mdll:
>>>--large-address-aware --tsaware}}}
>>>
>>>I'm trying to override this default.
>>
>> You're right that there isn't a way to disable --large-address-aware
>> but, since it's part of the specs, I'm not sure what would take
>> precedence if there was a --disable* option.
>>
>> You could try using the above to create your own spec file and use
>> that on the command line for gcc, cumbersome as it is.
>
>Reading the specs snippet --large-address-aware is only used if
>-shared and -mdll have *not* been specified, i.e. you are building
>with -static specified.  I think this is a bit strange but I don't
>know the reasoning behind it.

That's not what -shared means.

  -shared
       Produce a shared object which can then be linked with other
       objects to form an executable.

  -mdll
       This option is available for Cygwin and MinGW targets.  It
       specifies that a DLL - a dynamic link library - is to be
       generated, enabling the selection of the required runtime startup
       object and entry point.

These should be the default whenever you build an executable.  You can
verify yourself by specifying the -v option to gcc when linking
something.

cgf

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