Debian Bug report logs - #493465
libncurses5: allocates memory that is never freed

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Date: Sun, 3 Aug 2008 01:00:02 +0000
From: "brian m. carlson" <[email protected]>
To: Thomas Dickey <[email protected]>
Cc: [email protected]
Subject: Re: Bug#493465: libncurses5: allocates memory that is never freed
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On Sat, Aug 02, 2008 at 07:46:49PM -0400, Thomas Dickey wrote:
> On Sat, 2 Aug 2008, brian m. carlson wrote:
>
>> Package: libncurses5
>> Version: 5.6+20080713-1
>> Severity: normal
>>
>> According to valgrind, libncurses5 allocates approximately 118k that is
>> never freed:
>
> from INSTALL:
>
>     --disable-leaks
>         For testing, compile-in code that frees memory that normally would not
>         be freed, to simplify analysis of memory-leaks.
>
>         Any implementation of curses must not free the memory associated with
>         a screen, since (even after calling endwin()), it must be available
>         for use in the next call to refresh().  There are also chunks of
>         memory held for performance reasons.  That makes it hard to analyze
>         curses applications for memory leaks.  To work around this, build
>         a debugging version of the ncurses library which frees those chunks
>         which it can, and provides the _nc_free_and_exit() function to free
>         the remainder on exit.  The ncurses utility and test programs use this
>         feature, e.g., via the ExitProgram() macro.

This isn't really a solution unless the libncurses5 package is built
with it.  It's great that you considered this problem and built in an
option to fix it, but it's not compiled into the Debian package, and so
the Debian package leaks memory.  Shared libraries aren't supposed to do
that.

I personally don't believe refresh is required to work after a
delwin(stdscr), since

  Calling delwin deletes the named window, freeing all memory associated
  with it....

except that it doesn't free all the memory associated with it.  It does
free *some* of it, but not all.  I don't see any possible objection to
freeing all the related memory in this case, since calling refresh would
invoke undefined behavior.

-- 
brian m. carlson / brian with sandals: Houston, Texas, US
+1 713 440 7475 | http://crustytoothpaste.ath.cx/~bmc | My opinion only
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