Problems with: Improvements to fork handling (2/5)

Ryan Johnson
Sun May 29 02:36:00 GMT 2011

On 28/05/2011 8:23 PM, Christopher Faylor wrote:
> On Sat, May 28, 2011 at 06:40:30PM -0400, Ryan Johnson wrote:
>> On 28/05/2011 4:50 PM, Christopher Faylor wrote:
>>> On Wed, May 11, 2011 at 02:31:37PM -0400, Ryan Johnson wrote:
>>>> This patch has the parent sort its dll list topologically by
>>>> dependencies. Previously, attempts to load a DLL_LOAD dll risked pulling
>>>> in dependencies automatically, and the latter would then not benefit
>>> >from the code which "encourages" them to land in the right places. The
>>>> dependency tracking is achieved using a simple class which allows to
>>>> introspect a mapped dll image and pull out the dependencies it lists.
>>>> The code currently rebuilds the dependency list at every fork rather
>>>> than attempt to update it properly as modules are loaded and unloaded.
>>>> Note that the topsort optimization affects only cygwin dlls, so any
>>>> windows dlls which are pulled in dynamically (directly or indirectly)
>>>> will still impose the usual risk of address space clobbers.
>>> Bad news.
>>> I applied this patch and the one after it but then noticed that zsh started
>>> producing:  "bad address: " errors.
>>> path:4: bad address: /share/bin/dopath
>>> term:1: bad address: /bin/tee
>>> The errors disappear when I back this patch out.
>>> FWIW, I was running "zsh -l".  I have somewhat complicated
>>> .zshrc/.zlogin/.zshenv files.  I'll post them if needed.
>>> Until this is fixed, this patch and the subsequent ones which rely on
>>> it, can't go in.  I did commit this fix but it has been backed out now.
>> Hmm. I also see bad address errors in bash sometimes. However, when I
>> searched through the cygwin mailing list archives I saw that other
>> people have reported this problem in the past [1], so I figured it was
>> some existing, sporadic issue rather than my patch...
>> Could you tell me what a 'bad address' error is? I'd be happy to debug
>> this, but really don't know what kind of bug I'm hunting here, except
>> that it might be a problem wow64 and suspending threads [2]. Whatever
>> became of these bad address errors the last time(s) they cropped up? I
>> can't find any resolution with Google, at least.
> If I had any insight beyond "It works without the patch and it doesn't
> work with it" I would have shared it.
Let me rephrase a bit... The error happens too early in fork for gdb to 
be any help, and I was hoping you could tell me what part(s) of cygwin 
are capable of "raising" this error -- it seems to be a linux (not 
Windows) flavor of error message, but the case-insensitive regexp 
'bad.address' does not match anything in the cygwin sources.


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