I'd like to start out by thanking everyone for their help. While I did not
use a solution from the list, some of the advice did help me to better
search for a solution online. For the benefit of those who encounter this
problem in the future, I will share my solution below:
In a Perl program, do something like this:
sub test_image {
my ($size) = @_;
# allocate a block of memory and point to it
$image = create_image($size);
# manipulate the image
clear_image($image,$size);
# free the memory
destroy_image($image);
undef($image);
}
---------------------------------------------
ORIGINAL C CODE:
---------------------------------------------
char * create_image(int size) {
char * image;
New(0,image,size,char);
return image;
}
void clear_image(char * image,int size) {
memset(image,CLEAR,size);
}
void destroy_image(char * image) {
Safefree(image);
}
---------------------------------------------
This results in a segmentation fault. Using New() and Safefree() in the
same subroutine DOES free the memory properly, though. I should note this
works fine if you do not free the memory in the script (never call
destroy_image -- it will clean up when the script ends).
The following solution seems to work wonderfully, and required only minor
changes to my code:
---------------------------------------------
NEW C CODE:
---------------------------------------------
SV * create_image(int size) {
char * image;
New(0,image,size,char);
return sv_setref_pv(newSViv(0),"image", (void *)image);
}
void clear_image(SV * p,int size) {
char * image = (char *) SvIV(SvRV(p));
memset(image,CLEAR,size);
}
void destroy_image(SV * p) {
char * image = (char *) SvIV(SvRV(p));
Safefree(image);
}
---------------------------------------------
Basically, you cast the char * as an SV * when you create it and return it
to Perl, and cast it as a char * when you pass it into a subroutine.
Basically, I had to add one line of code to each subroutine (for each
pointer passed), and I could leave the rest of the code as it was.
I hope someone else finds this useful.
--
Dave
