Re: Interfaces.C.Strings chars_ptr memory management strategy

[ytomino <aghia05@gmail.com>]

On Monday, June 4, 2018 at 4:06:56 PM UTC+9, Dmitry A. Kazakov wrote:
> 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

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

That is only talking on the standard, probably is not the cause of the crash.