malloc: *** error for object 0x7ffc49c02850: pointer being freed was not allocated

fail.c

#define _POSIX_C_SOURCE 200112L

#include <search.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct st_symbol
{
	char *name;
	int type;
};

int always_equal(const void *a, const void *b)
{
	(void) a;
	(void) b;
	return 0;
}

int name_cmp(const void *a, const void* b)
{
	const struct st_symbol *u = a, *v = b;
	return strcmp(u->name, v->name);
}

bool st_add(struct st_symbol **tab, const char *s, int type)
{
	struct st_symbol *y = malloc(sizeof *y);
	if (!y) abort();
	y->name = strdup(s);
	y->type = type;
	if (!y->name) abort();

	struct st_symbol **node = tsearch(y, (void **)tab, name_cmp);
	if (!node)
		abort();
	return true;
}

void st_free(struct st_symbol **tab)
{
	while (*tab)
	{
		struct st_symbol *item = *tab;
		printf("deleting node: string = %s\n", item->name);
		tdelete(item, (void **)tab, always_equal);
		free(item->name);
		free(item);
	}
}

int main(void)
{
	struct st_symbol *g_words = NULL;

	st_add(&g_words, "hi", 1);
	st_free(&g_words);

	return 0;
}