I received a report of an error when a function is called from lispbuilder-sdl-mixer on the Mac in both SBCL and CCL.
I think the problem is that CFFI does not allow memory to be freed if that memory has not also been allocated using CFFI.
In my code below, a new 'sdl-version' struct is returned by (sdl-mixer-cffi::linked-version). The error seems to occur when I try to free the struct at the end of the function using foreign-free.
(defun linked-version () "Returns the version number of the SDL_mixer dynamic library in use as #(`MAJOR` `MINOR` `PATCH`)." (let ((sdl-version (sdl-mixer-cffi::linked-version)) (version nil)) (cffi:with-foreign-slots ((sdl-cffi::major sdl-cffi::minor sdl-cffi::patch) sdl-version sdl-cffi::sdl-version) (setf version (vector sdl-cffi::major sdl-cffi::minor sdl-cffi::patch))) (cffi:foreign-free sdl-version) version))
Can I get around this somehow?
-Luke
On Sat, May 21, 2011 at 1:21 AM, Luke Crook luke@balooga.com wrote:
I think the problem is that CFFI does not allow memory to be freed if that memory has not also been allocated using CFFI.
Indeed, you shouldn't call FOREIGN-FREE on pointers to memory not allocated by FOREIGN-ALLOC. You should be able to (defcfun free ...) and use that.
In my code below, a new 'sdl-version' struct is returned by (sdl-mixer-cffi::linked-version). The error seems to occur when I try to free the struct at the end of the function using foreign-free.
However, under SBCL FOREIGN-FREE is equivalent to free() -- not sure about CCL. According to SDL_Mixer's documentation, Mix_Linked_Version() returns a const pointer, so it seems that the bug here is that you're trying to free() non-malloc()ed memory.
HTH.
On Sun, May 22, 2011 at 2:10 PM, Luís Oliveira luismbo@gmail.com wrote:
On Sat, May 21, 2011 at 1:21 AM, Luke Crook luke@balooga.com wrote:
I think the problem is that CFFI does not allow memory to be freed if
that
memory has not also been allocated using CFFI.
Indeed, you shouldn't call FOREIGN-FREE on pointers to memory not allocated by FOREIGN-ALLOC. You should be able to (defcfun free ...) and use that.
In my code below, a new 'sdl-version' struct is returned by (sdl-mixer-cffi::linked-version). The error seems to occur when I try to free the struct at the end of the function using foreign-free.
However, under SBCL FOREIGN-FREE is equivalent to free() -- not sure about CCL. According to SDL_Mixer's documentation, Mix_Linked_Version() returns a const pointer, so it seems that the bug here is that you're trying to free() non-malloc()ed memory.
Thank you for pointing that out. I will fix that bug in my code.
/* rcg06192001 get linked library's version. */
139 http://hg.libsdl.org/SDL_mixer/file/4b699c9a269d/mixer.c#l139 const SDL_version *Mix_Linked_Version(void)
140 http://hg.libsdl.org/SDL_mixer/file/4b699c9a269d/mixer.c#l140 {
141 http://hg.libsdl.org/SDL_mixer/file/4b699c9a269d/mixer.c#l141 static SDL_version linked_version;
142 http://hg.libsdl.org/SDL_mixer/file/4b699c9a269d/mixer.c#l142 SDL_MIXER_VERSION(&linked_version);
143 http://hg.libsdl.org/SDL_mixer/file/4b699c9a269d/mixer.c#l143 return(&linked_version);
144 http://hg.libsdl.org/SDL_mixer/file/4b699c9a269d/mixer.c#l144 }
FYI; Lispworks doesn't complain about freeing the pointer.
-Luke
On Sun, 2011-05-22 at 23:19 -0700, Luke Crook wrote:
On Sun, May 22, 2011 at 2:10 PM, Luís Oliveira luismbo@gmail.com wrote:
On Sat, May 21, 2011 at 1:21 AM, Luke Crook luke@balooga.com wrote:
I think the problem is that CFFI does not allow memory to be freed if
that
memory has not also been allocated using CFFI.
Indeed, you shouldn't call FOREIGN-FREE on pointers to memory not allocated by FOREIGN-ALLOC. You should be able to (defcfun free ...) and use that.
In my code below, a new 'sdl-version' struct is returned by (sdl-mixer-cffi::linked-version). The error seems to occur when I try to free the struct at the end of the function using foreign-free.
However, under SBCL FOREIGN-FREE is equivalent to free() -- not sure about CCL. According to SDL_Mixer's documentation, Mix_Linked_Version() returns a const pointer, so it seems that the bug here is that you're trying to free() non-malloc()ed memory.
Thank you for pointing that out. I will fix that bug in my code.
/* rcg06192001 get linked library's version. */
139 http://hg.libsdl.org/SDL_mixer/file/4b699c9a269d/mixer.c#l139 const SDL_version *Mix_Linked_Version(void)
140 http://hg.libsdl.org/SDL_mixer/file/4b699c9a269d/mixer.c#l140 {
141 http://hg.libsdl.org/SDL_mixer/file/4b699c9a269d/mixer.c#l141 static SDL_version linked_version;
142 http://hg.libsdl.org/SDL_mixer/file/4b699c9a269d/mixer.c#l142 SDL_MIXER_VERSION(&linked_version);
143 http://hg.libsdl.org/SDL_mixer/file/4b699c9a269d/mixer.c#l143 return(&linked_version);
144 http://hg.libsdl.org/SDL_mixer/file/4b699c9a269d/mixer.c#l144 }
FYI; Lispworks doesn't complain about freeing the pointer.
Which probably means that Lispworks' foreign-free doesn't check that the pointer is valid, silently corrupting memory
-
Luke Crook -
Luís Oliveira -
Stelian Ionescu