[Docs] C producer examples leak memory?

[lord]

Describe the usage question you have. Please include as many useful details as possible.

Perhaps my limited C knowledge is making me miss something obvious, but I think the producer examples on this page of the documentation leak memory? Child schemas are malloced:

 //
 // Initialize child type #0
 //
 child = schema->children[0] = malloc(sizeof(struct ArrowSchema));

Then in the release implementation, we free the array of child pointers and call release on the children array, but don't actually free the child ArrowSchema allocations:

static void release_malloced_type(struct ArrowSchema* schema) {
   int i;
   for (i = 0; i < schema->n_children; ++i) {
      struct ArrowSchema* child = schema->children[i];
      if (child->release != NULL) {
         child->release(child);
      }
   }
   free(schema->children);
   // Mark released
   schema->release = NULL;
}

Since (as far as I can tell?) the docs don't otherwise explicitly state what the lifetime of these children is, it could be nice to fix this? Reading the C++ ExportArray implementation, it seems like these are in fact freed in the release call via the private_data pointer in at least the C++ implementation.

Component(s)

C, Documentation

[zeroshade]

The docs specify the lifetime and memory management semantics here: https://arrow.apache.org/docs/format/CDataInterface.html#memory-management

That said, it looks like you're right. There should be a free(child); after child->release(child); Would you be willing to contribute a PR to fix it? 😄