[Gridflow-dev] read PNG memory leak patch (untested!)

[Claude Heiland-Allen]

Hi matju, all,

I reported a memory leak on #dataflow; basically after reading 30000+ 
PNG images, Pd+GridFlow uses 300MB+ ram...

I think I found the solution, it involves explicitly reading the png 
info at the end of the file and also explicitly freeing it, as opposed 
to pretending there isn't any extra data...

Note: I haven't tested this, having trouble compiling gridflow cvs on 
pure:dyne, but I've adapted this patched png.c code in a standalone 
program without any memory leaks.

Hope this is useful...

Claude

(~/pd/gridflow/format) # diff -uw png.c.orig png.c
--- png.c.orig  2007-07-03 07:48:16.000000000 +0000
+++ png.c       2007-07-03 07:51:02.000000000 +0000
@@ -34,6 +34,7 @@
         P<BitPacking> bit_packing;
         png_structp png;
         png_infop info;
+       png_infop infoend;
         int fd;
         FILE *f;
         FormatPNG () : bit_packing(0), png(0), f(0) {}
@@ -71,6 +72,10 @@
         if (!info) {
                 png_destroy_read_struct(&png, NULL, NULL); RAISE("!info");
         }
+       infoend = png_create_info_struct(png);
+       if (!infoend) {
+               png_destroy_read_struct(&png, NULL, NULL); 
RAISE("!infoend");
+       }
         if (setjmp(png_jmpbuf(png))) {
                 png_destroy_read_struct(&png, &info, NULL); RAISE("png 
read error");
         }
@@ -108,13 +113,13 @@
         png_read_image(png, row_pointers);
         delete row_pointers;
         row_pointers = 0;
-       png_read_end(png, 0);
+       png_read_end(png, infoend);

         GridOutlet out(this,0,new Dim(height, width, channels),
                 NumberTypeE_find(rb_ivar_get(rself,SI(@cast))));
         out.send(rowbytes*height,image_data);
         free(image_data);
-       png_destroy_read_struct(&png, &info, NULL);
+       png_destroy_read_struct(&png, &info, &infoend);
         return Qnil;
  }

zsh: exit 1     diff -uw png.c.orig png.c