From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00
	autolearn=unavailable autolearn_force=no version=3.4.4
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail
From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Interfaces.C.Strings chars_ptr memory management strategy
Date: Mon, 4 Jun 2018 09:06:54 +0200
Organization: Aioe.org NNTP Server
Message-ID: <pf2oed$35f$1@gioia.aioe.org>
References: <6ff31dc6-31e7-4755-bda0-1b53fa02f31f@googlegroups.com>
 <735fd76c-c0a7-4e8c-a534-857772cada9b@googlegroups.com>
 <pf1fps$4rv$1@gioia.aioe.org>
 <8816050d-27e6-42e2-b6e8-fd85b31e8e04@googlegroups.com>
NNTP-Posting-Host: MyFhHs417jM9AgzRpXn7yg.user.gioia.aioe.org
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
X-Complaints-To: abuse@aioe.org
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.8.0
X-Notice: Filtered by postfilter v. 0.8.3
Content-Language: en-US
Xref: reader02.eternal-september.org comp.lang.ada:52911
Date: 2018-06-04T09:06:54+02:00
List-Id: <comp.lang.ada>

On 2018-06-03 10:03 PM, ytomino wrote:
> On Monday, June 4, 2018 at 4:33:20 AM UTC+9, Dmitry A. Kazakov wrote:
>> On 2018-06-03 20:31, ytomino wrote:
>>> Perhaps, malloc is better than New_String in this case.
>>>
>>>    function malloc (s : Interfaces.C.size_t) return Interfaces.C.Strings.chars_ptr
>>>       with Import, Convention => C;
>>
>> I had a case when that caused the application crashed.
>>
>> I guess it was because of mixed Visual Studio and GCC run-times. The
>> pointer returned by the malloc from one was freed in a third-party C
>> library by another.
>>
>> -- 
>> Regards,
>> Dmitry A. Kazakov
>> http://www.dmitry-kazakov.de
> 
> What!?
> 
> New_String calls malloc in the end, too, in mingw runtime.
> (It calls Memory_Alloc, Memory_Alloc is _gnat_malloc, and __gnat_malloc calls malloc.)
> https://gcc.gnu.org/svn/gcc/trunk/gcc/ada/libgnat/i-cstrin.adb
> https://gcc.gnu.org/svn/gcc/trunk/gcc/ada/libgnat/s-parame.ads
> https://gcc.gnu.org/svn/gcc/trunk/gcc/ada/libgnat/s-memory__mingw.adb
> 
> If Interfaces.C.Strings.Free (malloc) is crashed, New_String would be same.

No, not this free but the one called from the third-party library 
because the pointer was passed there to handle.

Of course it is safe to call malloc-free or New_String-Free pairs. Other 
combinations can be unsafe.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de