8 files changed, 101 insertions, 23 deletions
diff --git a/tests/Makefile b/tests/Makefile
index 31f0cc240..ff3504ead 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -12,7 +12,7 @@ PROGS = test1 test2 test3 test4 test5 test6 test7 test8 test9   \
         test66 test67 test68 test69 test70 test71 test72 test73 \
         test74 test75 test76 test77 test78 test79 test80 test81 \
         test82 test83 test84 test85 test86 test87 test88 test89 \
-        test90 test91 test92 test93 test94 test95 test96
+        test90 test91 test92 test93 test94 test95 test96 test97
 CFLAGS += -I$(HASHDIR)
 #CFLAGS += -DHASH_BLOOM=16
 #CFLAGS += -O2
diff --git a/tests/README b/tests/README
index a287de670..747661dd0 100644
--- a/tests/README
+++ b/tests/README
@@ -98,6 +98,7 @@ test93: alt_fatal
 test94: utlist with fields named other than 'next' and 'prev'
 test95: utstack
 test96: HASH_FUNCTION + HASH_KEYCMP
+test97: deleting a const-qualified node from a hash
 
 Other Make targets
 ================================================================================
diff --git a/tests/hashscan.c b/tests/hashscan.c
index d18b364ef..dc581f2dd 100644
--- a/tests/hashscan.c
+++ b/tests/hashscan.c
@@ -1,5 +1,5 @@
 /*
-Copyright (c) 2005-2021, Troy D. Hanson    http://troydhanson.github.io/uthash/
+Copyright (c) 2005-2022, Troy D. Hanson  https://troydhanson.github.io/uthash/
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
diff --git a/tests/test57.ans b/tests/test57.ans
index 4d3bb1d0b..e69de29bb 100644
--- a/tests/test57.ans
+++ b/tests/test57.ans
@@ -1 +0,0 @@
-found
diff --git a/tests/test57.c b/tests/test57.c
index 3b89fb52d..7ba3b81ae 100644
--- a/tests/test57.c
+++ b/tests/test57.c
@@ -1,5 +1,5 @@
-#include <stdio.h>
-#include <stdlib.h>
+#include <assert.h>
+#include <stddef.h>
 #include "uthash.h"
 
 typedef struct {
@@ -8,25 +8,46 @@ typedef struct {
     UT_hash_handle hh;
 } el_t;
 
+el_t *findit(el_t *hash, void *keytofind)
+{
+    el_t *found;
+    HASH_FIND_PTR(hash, &keytofind, found);
+    return found;
+}
+
 int main()
 {
-    el_t *d;
     el_t *hash = NULL;
-    char *someaddr = NULL;
-    el_t *e = (el_t*)malloc(sizeof(el_t));
-    if (!e) {
-        return -1;
-    }
-    e->key = (void*)someaddr;
-    e->i = 1;
-    HASH_ADD_PTR(hash,key,e);
-    HASH_FIND_PTR(hash, &someaddr, d);
-    if (d != NULL) {
-        printf("found\n");
-    }
-
-    /* release memory */
-    HASH_DEL(hash,e);
-    free(e);
+    el_t e1;
+    el_t e2;
+
+    e1.key = NULL;
+    e1.i = 1;
+
+    e2.key = &e2;
+    e2.i = 2;
+
+    assert(findit(hash, NULL) == NULL);
+    assert(findit(hash, &e1) == NULL);
+    assert(findit(hash, &e2) == NULL);
+
+    HASH_ADD_PTR(hash, key, &e1);
+    assert(findit(hash, NULL) == &e1);
+    assert(findit(hash, &e1) == NULL);
+    assert(findit(hash, &e2) == NULL);
+
+    HASH_ADD_PTR(hash, key, &e2);
+    assert(findit(hash, NULL) == &e1);
+    assert(findit(hash, &e1) == NULL);
+    assert(findit(hash, &e2) == &e2);
+
+    HASH_DEL(hash, &e1);
+    assert(findit(hash, NULL) == NULL);
+    assert(findit(hash, &e1) == NULL);
+    assert(findit(hash, &e2) == &e2);
+
+    HASH_CLEAR(hh, hash);
+    assert(hash == NULL);
+
     return 0;
 }
diff --git a/tests/test65.c b/tests/test65.c
index 0584fb1a0..5820a4552 100644
--- a/tests/test65.c
+++ b/tests/test65.c
@@ -3,7 +3,7 @@
 #include "uthash.h"
 
 // this is an example of how to do a LRU cache in C using uthash
-// http://troydhanson.github.io/uthash/
+// https://troydhanson.github.io/uthash/
 // by Jehiah Czebotar 2011 - jehiah@gmail.com
 // this code is in the public domain http://unlicense.org/
 
diff --git a/tests/test97.ans b/tests/test97.ans
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/tests/test97.ans
diff --git a/tests/test97.c b/tests/test97.c
new file mode 100644
index 000000000..d59008bac
--- /dev/null
+++ b/tests/test97.c
@@ -0,0 +1,57 @@
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+#include "uthash.h"
+
+struct item {
+    int payload;
+    UT_hash_handle hh;
+};
+
+void delete_without_modifying(struct item *head, const struct item *p)
+{
+    struct item old;
+    memcpy(&old, p, sizeof(struct item)); // also copy the padding bits
+    assert(memcmp(&old, p, sizeof(struct item)) == 0);
+    assert(p->hh.tbl == head->hh.tbl); // class invariant
+    HASH_DEL(head, p);
+    assert(memcmp(&old, p, sizeof(struct item)) == 0);  // unmodified by HASH_DEL
+}
+
+int main()
+{
+    struct item *items = NULL;
+    struct item *found = NULL;
+    int fortytwo = 42;
+    int i;
+
+    for (i=0; i < 100; i++) {
+        struct item *p = (struct item *)malloc(sizeof *p);
+        p->payload = i;
+        HASH_ADD_INT(items, payload, p);
+    }
+    assert(HASH_COUNT(items) == 100);
+
+    // Delete item "42" from the hash, wherever it is.
+    HASH_FIND_INT(items, &fortytwo, found);
+    assert(found != NULL);
+    assert(found->payload == 42);
+    delete_without_modifying(items, found);
+
+    assert(HASH_COUNT(items) == 99);
+    HASH_FIND_INT(items, &fortytwo, found);
+    assert(found == NULL);
+
+    // Delete the very first item in the hash.
+    assert(items != NULL);
+    i = items->payload;
+    delete_without_modifying(items, items);
+
+    assert(HASH_COUNT(items) == 98);
+    HASH_FIND_INT(items, &i, found);
+    assert(found == NULL);
+
+    // leak the items, we don't care
+
+    return 0;
+}