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Re: [PATCH] setup.exe SEGV on WinXP/Pro
- From: Christopher Faylor <cgf-use-the-mailinglist-please at cygwin dot com>
- To: cygwin-apps at cygwin dot com
- Date: Fri, 9 Aug 2013 12:55:13 -0400
- Subject: Re: [PATCH] setup.exe SEGV on WinXP/Pro
- References: <877gfw2fqp dot fsf at Rainer dot invalid> <20130809090726 dot GS16868 at calimero dot vinschen dot de> <20130809153313 dot GA2312 at ednor dot casa dot cgf dot cx> <786EBDA1AC46254B813E200779E7AD3602FF22B6 at srv1163ex1 dot flightsafety dot com>
- Reply-to: cygwin-apps at cygwin dot com
On Fri, Aug 09, 2013 at 11:01:32AM -0500, Thrall, Bryan wrote:
>Christopher Faylor wrote on 2013-08-09:
>> On Fri, Aug 09, 2013 at 11:07:26AM +0200, Corinna Vinschen wrote:
>>> On Aug 8 20:34, Achim Gratz wrote:
>>>>
>>>> I've been having sporadic SEGV on WinXP/Pro just after the MD5 of a
>>>> package was checked that used to clear up after a reboot. Today,
>with a
>>>> freshly built setup.exe this failure was now entirely reproduceable.
>>>> I've fixed it by reimplementing the string formatting for the MD5
>digest
>>>> using C++ stream functions.
>>>>
>>>
>>>>> From 677e2e89d1e4046c967dd1759ac53116f6643bd9 Mon Sep 17
>> 00:00:00 2001
>>>> From: Achim Gratz <Stromeko@Stromeko.DE>
>>>> Date: Thu, 8 Aug 2013 20:23:31 +0200
>>>> Subject: [PATCH] fix SEGV on WinXP/Pro
>>>>
>>>> * csu_util/MD5Sum.cc (MD5Sum::operator std::string() const):
>>>> Reimplement using stringstream to avoid a SEGV on WinXP/Pro.
>>>
>>> Patch applied.
>>>
>>>> - return std::string(hexdigest);
>>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>> I'm wondering if that was the problem. This expression constructs a
>>> std:string and then immediately destructs it since the scope is
>limited
>>> to the end of the function (which the return statement is all about).
>>> Reading the value of this object in the parent function is basically
>>> luck, isn't it?
>>
>> Sheesh. Yes, that looks like the problem. But doesn't the new code
>do
>> pretty much the same thing?
>>
>> + std::ostringstream hexdigest;
>> + return hexdigest.str();
>
>According to this:
>
>http://stackoverflow.com/questions/275214/scope-and-return-values-in-c
>
>Returning the object should be ok because it is copied before leaving
>the function scope; returning a reference or pointer to the object is
>where you get into problems.
Thanks for clarifying. Isn't that what the original code did too then?
cgf