# SDL\_mixer: fix mikmod malloc/free mismatch - cause of crashe

**URL:** <https://discourse.libsdl.org/t/sdl-mixer-fix-mikmod-malloc-free-mismatch-cause-of-crashe/19020>\
**Category:** SDL Development\
**Created:** [July 23, 2012, 10:46am UTC](https://discourse.libsdl.org/t/sdl-mixer-fix-mikmod-malloc-free-mismatch-cause-of-crashe/19020 "2012-07-23T10:46:25Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![stevo5800](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/s/bcef8e/32.png) [@stevo5800](https://discourse.libsdl.org/u/stevo5800)\
**Post date:** [July 23, 2012, 10:46am UTC](https://discourse.libsdl.org/t/sdl-mixer-fix-mikmod-malloc-free-mismatch-cause-of-crashe/19020/1 "2012-07-23T10:46:25Z")

</div>

you can check on mercurial and see what patches have been added [GitHub - libsdl-org/SDL\_mixer: An audio mixer that supports various file formats for Simple Directmedia Layer.](http://hg.libsdl.org/SDL_mixer/) seems the patch was added yesterday

R Manard wrote:\> You?say I made some good points. Thank you. I remember times when fixes to sdl were offered?where it was a disaster to be avoided. Learning from the past I wanted to make the points that should have seemed obviouse, in my opinion. Blanks to fill in. Procedure to follow.?When I said that maybe the fix was the best thing anyone could do, it was?saying that there might?be no cause for any alarm and simply be top notch world class work that is now finished. Sam must think this is true. Having the familliarity?with sdl?I believe he opened it up and?understood it to be a true and current fix. That’s good enough for me.

> I don’t like to talk about language or nationality. Sometimes I don’t use the word that I think it is. I don’t extend different treatment to people but assume everyone uses the wrong word sometimes.  
> ?  
> If I download the mixer will the fix be in it? Does anyone know?
> 
> On Sun, Jul 22, 2012 at 8:24 PM, Jared Maddox \<absinthdraco at [gmail.com](http://gmail.com) (absinthdraco at [gmail.com](http://gmail.com))\> wrote:
> 
> > > Date: Sun, 22 Jul 2012 17:14:21 -0500
> > 
> > > From: R Manard \<dranikist at [gmail.com](http://gmail.com) (dranikist at [gmail.com](http://gmail.com))\>  
> > > To: SDL Development List \<sdl at [lists.libsdl.org](http://lists.libsdl.org) (sdl at [lists.libsdl.org](http://lists.libsdl.org))\>  
> > > Subject: Re: [SDL] SDL\_mixer: fix mikmod malloc/free mismatch - cause  
> > > ? ? ? of crashes on systems that check for that.  
> > > Message-ID:  
> > > ? ? ? \<CAKCUQMYdzdtYZRCkkLpivkv4gbZ=WsawwF\_4wqj\_XgWL87WshA at [mail.gmail.com](http://mail.gmail.com) (WsawwF\_4wqj\_XgWL87WshA at [mail.gmail.com](http://mail.gmail.com))\>  
> > > Content-Type: text/plain; charset=“iso-8859-1”
> > 
> > Sam applying the patch pretty much answers your points, but I figured  
> > that I should point out some relevant details (especially since I  
> > half-recall reading that you were French, and thus might need some  
> > language tips).
> > 
> > > On Sun, Jul 22, 2012 at 8:14 AM, Paul P Komkoff Jr \<i at [stingr.net](http://stingr.net) (i at [stingr.net](http://stingr.net))\> wrote:
> > 
> > > > With the little help I tracked the crash down and wrote a test case  
> > > > that reproduces it perfectly:
> > > > 
> > > > #include \<mikmod.h\>  
> > > > main()  
> > > > {  
> > > > ? ? ? ? MikMod\_RegisterAllDrivers();  
> > > > ? ? ? ? MikMod\_Init(“”);  
> > > > ? ? ? ? char\* d = MikMod\_InfoDriver();  
> > > > ? ? ? ? if (d) {  
> > > > ? ? ? ? ? printf(“%s\n”, d);  
> > > > ? ? ? ? ? free(d);  
> > > > ? ? ? ? }  
> > > > ? ? ? ? MikMod\_Exit();  
> > > > }
> > > > 
> > > > The crash happens at free(), where glibc will detect “double-free or  
> > > > corruption”. This is happening because mikmod uses MikMod\_malloc() to  
> > > > allocate memory for return value, and MikMod\_malloc() does some funny  
> > > > things with allocations and alignments. Replacing free() with  
> > > > MikMod\_free() is enough to stop crashes.
> > 
> > > If something sdl uses is broken and then something else uses sdl that would  
> > > change things or if your stuff now works but now most other people’s stuff  
> > > is broke because of the way it was fixed that would be bad.
> > 
> > You see that bit where mikmod has it’s own free() function, but SDL  
> > wasn’t using it in the necessary situations? That needed to be fixed.  
> > If programs or libraries were depending on that, (which is highly  
> > unlikely, since it was producing crashes), then they need to be fixed.  
> > The change to SDL (regardless of whether it works perfectly with the  
> > first patch) is the correct thing to do, because SDL had the wrong  
> > behavior. If the change breaks something, then it was the fault of the  
> > thing that broke.
> > 
> > Preserving bugs because something uses them is WRONG. I realize that  
> > Microsoft does it with Windows, but (especially with the early  
> > versions, where such anecdotes seem the most common) Windows was  
> > historically considered buggy and prone to viruses, partially because  
> > of those intentionally preserved bugs. Better to deal with it up-front  
> > (especially since API-breakage should still be expected in the 2.0  
> > series) than to let it fester.
> > 
> > > What if it’s an  
> > > old version and it was fixed two versions ago?
> > 
> > Then the patch gets ignored, unless it is an improvement on the old  
> > fix, in which case Sam & co. decide whether to replace the old patch  
> > with the new. But yes, Paul should have listed the actual version that  
> > he applied the patch to.
> > 
> > One last thing. Your response was toned too harshly. In particular, it  
> > was written as if you were trying to discourage Paul from posting  
> > patches, and if I ignored that implication then it seemed like you  
> > were panicking about the possibilities that you mentioned. I doubt  
> > that you intended the first of those interpretations, but in case the  
> > second was true, I’ll say this:
> > 
> > Stop worrying so much, the cost of those mistakes is very small so  
> > there’s no problem if they happen. Even more importantly, nothing will  
> > improve if nothing changes, and successfully crowd-sourced projects  
> > move faster than ones with only two or three people working on them.
> > 
> > In the words of Douglas Adams: Don’t Panic.
> > 
> > * * *
> > 
> > SDL mailing list  
> > SDL at [lists.libsdl.org](http://lists.libsdl.org) (SDL at [lists.libsdl.org](http://lists.libsdl.org))  
> > [http://lists.libsdl.org/listinfo.cgi/sdl-libsdl.org](http://lists.libsdl.org/listinfo.cgi/sdl-libsdl.org) ([http://lists.libsdl.org/listinfo.cgi/sdl-libsdl.org](http://lists.libsdl.org/listinfo.cgi/sdl-libsdl.org))

---

<div class="post-metadata">

**Author:** ![R\_Manard](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/r/46a35a/32.png) [@R\_Manard](https://discourse.libsdl.org/u/R_Manard)\
**Post date:** [July 23, 2012, 6:41pm UTC](https://discourse.libsdl.org/t/sdl-mixer-fix-mikmod-malloc-free-mismatch-cause-of-crashe/19020/2 "2012-07-23T18:41:51Z")

</div>

I only use release versions but thank you the sameOn Mon, Jul 23, 2012 at 5:46 AM, stevo5800 wrote:

> \*\*  
> you can check on mercurial and see what patches have been added  
> [GitHub - libsdl-org/SDL\_mixer: An audio mixer that supports various file formats for Simple Directmedia Layer.](http://hg.libsdl.org/SDL_mixer/) seems the patch was added yesterday
> 
> R Manard wrote:
> 
> You say I made some good points. Thank you. I remember times when fixes to  
> sdl were offered where it was a disaster to be avoided. Learning from the  
> past I wanted to make the points that should have seemed obviouse, in my  
> opinion. Blanks to fill in. Procedure to follow. When I said that maybe the  
> fix was the best thing anyone could do, it was saying that there might be  
> no cause for any alarm and simply be top notch world class work that is now  
> finished. Sam must think this is true. Having the familliarity with sdl I  
> believe he opened it up and understood it to be a true and current fix.  
> That’s good enough for me.  
> I don’t like to talk about language or nationality. Sometimes I don’t use  
> the word that I think it is. I don’t extend different treatment to people  
> but assume everyone uses the wrong word sometimes.
> 
> If I download the mixer will the fix be in it? Does anyone know?
> 
> On Sun, Jul 22, 2012 at 8:24 PM, Jared Maddox \<\> wrote:
> 
> Quote:
> 
> > Date: Sun, 22 Jul 2012 17:14:21 -0500
> 
> Quote:
> 
> From: R Manard \<\>  
> To: SDL Development List \<\>  
> Subject: Re: [SDL] SDL\_mixer: fix mikmod malloc/free mismatch - cause  
> of crashes on systems that check for that.  
> Message-ID:  
> \*\*  
> Content-Type: text/plain; charset=“iso-8859-1”
> 
> Sam applying the patch pretty much answers your points, but I figured  
> that I should point out some relevant details (especially since I  
> half-recall reading that you were French, and thus might need some  
> language tips).
> 
> Quote:
> 
> On Sun, Jul 22, 2012 at 8:14 AM, Paul P Komkoff Jr \<\> wrote:
> 
> Quote:
> 
> Quote:
> 
> With the little help I tracked the crash down and wrote a test case  
> that reproduces it perfectly:
> 
> #include \*\*  
> main()  
> {  
> MikMod\_RegisterAllDrivers();  
> MikMod\_Init(“”);  
> char\* d = MikMod\_InfoDriver();  
> if (d) {  
> printf(“%s\n”, d);  
> free(d);  
> }  
> MikMod\_Exit();  
> }
> 
> The crash happens at free(), where glibc will detect “double-free or  
> corruption”. This is happening because mikmod uses MikMod\_malloc() to  
> allocate memory for return value, and MikMod\_malloc() does some funny  
> things with allocations and alignments. Replacing free() with  
> MikMod\_free() is enough to stop crashes.
> 
> Quote:
> 
> If something sdl uses is broken and then something else uses sdl that would  
> change things or if your stuff now works but now most other people’s stuff  
> is broke because of the way it was fixed that would be bad.
> 
> You see that bit where mikmod has it’s own free() function, but SDL  
> wasn’t using it in the necessary situations? That needed to be fixed.  
> If programs or libraries were depending on that, (which is highly  
> unlikely, since it was producing crashes), then they need to be fixed.  
> The change to SDL (regardless of whether it works perfectly with the  
> first patch) is the correct thing to do, because SDL had the wrong  
> behavior. If the change breaks something, then it was the fault of the  
> thing that broke.
> 
> Preserving bugs because something uses them is WRONG. I realize that  
> Microsoft does it with Windows, but (especially with the early  
> versions, where such anecdotes seem the most common) Windows was  
> historically considered buggy and prone to viruses, partially because  
> of those intentionally preserved bugs. Better to deal with it up-front  
> (especially since API-breakage should still be expected in the 2.0  
> series) than to let it fester.
> 
> Quote:
> 
> What if it’s an  
> old version and it was fixed two versions ago?
> 
> Then the patch gets ignored, unless it is an improvement on the old  
> fix, in which case Sam & co. decide whether to replace the old patch  
> with the new. But yes, Paul should have listed the actual version that  
> he applied the patch to.
> 
> One last thing. Your response was toned too harshly. In particular, it  
> was written as if you were trying to discourage Paul from posting  
> patches, and if I ignored that implication then it seemed like you  
> were panicking about the possibilities that you mentioned. I doubt  
> that you intended the first of those interpretations, but in case the  
> second was true, I’ll say this:
> 
> Stop worrying so much, the cost of those mistakes is very small so  
> there’s no problem if they happen. Even more importantly, nothing will  
> improve if nothing changes, and successfully crowd-sourced projects  
> move faster than ones with only two or three people working on them.
> 
> In the words of Douglas Adams: Don’t Panic.
> 
> * * *
> 
> SDL mailing list
> 
> [http://lists.libsdl.org/listinfo.cgi/sdl-libsdl.org](http://lists.libsdl.org/listinfo.cgi/sdl-libsdl.org)
> 
> * * *
> 
> SDL mailing list  
> SDL at [lists.libsdl.org](http://lists.libsdl.org)  
> [http://lists.libsdl.org/listinfo.cgi/sdl-libsdl.org](http://lists.libsdl.org/listinfo.cgi/sdl-libsdl.org)