Add test and remove code comments

.gitignore

@@ -1,2 +1,4 @@
 test
-test.exe
+test.exe
+test2
+test2.exe

buddy.c

@@ -547,8 +547,12 @@ void *buddy_malloc(struct buddy_alloc *alloc, size_t len)
 void buddy_free(struct buddy_alloc *alloc,
                 size_t len, void *ptr)
 {
-    if (ptr == NULL || len == 0) return;
+    if (ptr == NULL || len == 0)
-    if (len > MAX_BLOCK_SIZE) return;
+        return;
+
+    if (len > MAX_BLOCK_SIZE)
+        return;
+
     len = normalize_len(len);
 
     if (!is_allocated(alloc, ptr, len))
@@ -571,83 +575,3 @@ void buddy_free(struct buddy_alloc *alloc,
         len <<= 1;
     }
 }
-
-/*
-#define ANSI_COLOR_RED     "\x1b[31m"
-#define ANSI_COLOR_GREEN   "\x1b[32m"
-#define ANSI_COLOR_YELLOW  "\x1b[33m"
-#define ANSI_COLOR_BLUE    "\x1b[34m"
-#define ANSI_COLOR_MAGENTA "\x1b[35m"
-#define ANSI_COLOR_CYAN    "\x1b[36m"
-#define ANSI_COLOR_RESET   "\x1b[0m"
-
-static const char *block_size_label(size_t len)
-{
-    const char *label = "???";
-    switch (len) {
-        case 1<<12: label = "4K"; break;
-        case 1<<11: label = "2K"; break;
-        case 1<<10: label = "1K"; break;
-        case 1<<9 : label = "512B"; break;
-        case 1<<8 : label = "256B"; break;
-    }
-    return label;
-}
-
-void print_lists(struct buddy_alloc *alloc)
-{
-    for (int i = MIN_BLOCK_LOG2; i <= MAX_BLOCK_LOG2; i++) {
-        fprintf(stderr, "%s = {", block_size_label(1U<<i));
-        struct page *p = alloc->lists[i - MIN_BLOCK_LOG2];
-        while (p) {
-            assert((uintptr_t) p >= (uintptr_t) alloc->base);
-            fprintf(stderr, "%lu", (uintptr_t) p - (uintptr_t) alloc->base);
-            p = p->next;
-            if (p)
-                fprintf(stderr, ", ");
-        }
-        fprintf(stderr, "}\n");
-    }
-}
-
-void buddy_dump(struct buddy_alloc *alloc, FILE *out)
-{
-    fprintf(out, "\n");
-
-    for (int i = 0; i < alloc->num_info; i++) {
-        for (int j = 0; j < 32; j++) {
-            if (alloc->info[i].bits[0] & (1U << j))
-                fprintf(stderr, "1");
-            else
-                fprintf(stderr, "0");
-        }
-        fprintf(stderr, " ");
-    }
-    fprintf(stderr, "\n");
-
-    for (int i = 0; i < alloc->num_info; i++) {
-        char *page = alloc->base + i * MAX_BLOCK_SIZE;
-        for (int j = MAX_BLOCK_LOG2; j >= MIN_BLOCK_LOG2; j--) {
-
-            size_t len = 1U << j;
-
-            const char *label = block_size_label(len);
-
-            for (size_t k = 0; k < MAX_BLOCK_SIZE / len; k++) {
-
-                char *ptr = page + k * len;
-
-                fprintf(out, "%-4lX ", (uintptr_t) ptr - (uintptr_t) alloc->base);
-
-                for (int q = 0; q < MAX_BLOCK_LOG2 - j; q++)
-                    fprintf(out, "  ");
-
-                if (is_allocated(alloc, ptr, len))
-                    fprintf(out, ANSI_COLOR_GREEN "%s - allocated\n" ANSI_COLOR_RESET, label);
-                else
-                    fprintf(out, "%s - free\n", label);
-            }
-        }
-    }
-}
-*/

buddy.h

@@ -1,23 +1,25 @@
 #include <stddef.h>
 #include <stdint.h>
 
-#define BUDDY_ALLOC_MAX_BLOCK_LOG2 12
+#define BUDDY_ALLOC_MAX_BLOCK_LOG2 13
-#define BUDDY_ALLOC_MIN_BLOCK_LOG2 8
+#define BUDDY_ALLOC_MIN_BLOCK_LOG2 3
+
+_Static_assert(BUDDY_ALLOC_MIN_BLOCK_LOG2 <= BUDDY_ALLOC_MAX_BLOCK_LOG2);
+_Static_assert(BUDDY_ALLOC_MIN_BLOCK_LOG2 > 2);
+
 #define BUDDY_ALLOC_NUM_LISTS (BUDDY_ALLOC_MAX_BLOCK_LOG2 - BUDDY_ALLOC_MIN_BLOCK_LOG2 + 1)
 
-/*
+// To keep track of the allocation state of a page,
- * To keep track of the allocation state of a page,
+// we need one bit for each possible block that can
- * we need one bit for each possible block that can
+// be made out of it. For instance, if the page can
- * be made out of it. For instance, if the page can
+// only be allocated in its entirety, 1 bit is required.
- * only be allocated in its entirety, 1 bit is required.
+// If the blocks halfs can be allocated too, 3 bits
- * If the blocks halfs can be allocated too, 3 bits
+// are required: 1 for the page, 1 for the frist half
- * are required: 1 for the page, 1 for the frist half
+// and 1 for the second half. Allowing the allocation
- * and 1 for the second half. Allowing the allocation
+// of page quarters requires 4 more bits, for a total
- * of page quarters requires 4 more bits, for a total
+// of 7. In general, if we allow splitting a page N
- * of 7. In general, if we allow splitting a page N
+// times (N=0 means only the entire page can be allocated),
- * times (N=0 means only the entire page can be allocated),
+// then 2^(N+1)-1 bits are necessary.
- * then 2^(N+1)-1 bits are necessary.
- */
 #define BUDDY_ALLOC_BITS_PER_PAGE ((1U << (BUDDY_ALLOC_NUM_LISTS)) - 1)
 #define BUDDY_ALLOC_WORDS_PER_PAGE ((BUDDY_ALLOC_BITS_PER_PAGE + 31) / 32)
 

makefile

@@ -1,3 +1,4 @@
 
 all:
-	gcc test.c buddy.c -o test -Wall -Wextra -ggdb #-fsanitize=address,undefined
+	gcc test.c  buddy.c -o test  -Wall -Wextra -ggdb #-fsanitize=address,undefined
+	gcc test2.c buddy.c -o test2 -Wall -Wextra -ggdb

test2.c

@@ -0,0 +1,63 @@
+#include <stdio.h>
+#include "buddy.h"
+
+#define NUM_PAGES 16
+
+#define MIN_ALLOC_SIZE (1U << BUDDY_ALLOC_MIN_BLOCK_LOG2)
+#define PAGE_SIZE (1U << BUDDY_ALLOC_MAX_BLOCK_LOG2)
+#define POOL_SIZE (NUM_PAGES * PAGE_SIZE)
+#define MAX_ALLOCS (POOL_SIZE / MIN_ALLOC_SIZE)
+
+int main(void)
+{
+    _Alignas(PAGE_SIZE) char mem[POOL_SIZE];
+    struct page_info info[NUM_PAGES];
+    struct buddy_alloc alloc = buddy_startup(mem, POOL_SIZE, info, NUM_PAGES);
+
+    void *allocs[MAX_ALLOCS];
+
+    size_t performed = 0;
+    for (size_t i = 0; i < MAX_ALLOCS; i++) {
+        void *ptr = buddy_malloc(&alloc, MIN_ALLOC_SIZE);
+        if (ptr == NULL)
+            break;
+        
+        performed++;
+
+        allocs[i] = ptr;
+
+        *(size_t*) ptr = i;
+    }
+
+    if (performed == MAX_ALLOCS) {
+
+        for (size_t i = 0; i < MAX_ALLOCS; i++) {
+            if (*(size_t*) allocs[i] != i)
+                fprintf(stderr, "%p allocated twice!\n", allocs[i]);
+        }
+
+        for (size_t i = 0; i < MAX_ALLOCS; i++) {
+            buddy_free(&alloc, MIN_ALLOC_SIZE, allocs[MAX_ALLOCS-i-1]);
+        }
+
+        performed = 0;
+        for (size_t i = 0; i < MAX_ALLOCS; i++) {
+            void *ptr = buddy_malloc(&alloc, MIN_ALLOC_SIZE);
+            performed++;
+
+            allocs[i] = ptr;
+
+            *(size_t*) ptr = i + MAX_ALLOCS;
+        }
+
+        for (size_t i = 0; i < MAX_ALLOCS; i++) {
+            if (*(size_t*) allocs[i] != MAX_ALLOCS + i)
+                fprintf(stderr, "%p reallocation error!\n", allocs[i]);
+        }
+    }
+
+    fprintf(stderr, "performed=%lu, expected=%u\n", performed, MAX_ALLOCS);
+
+    buddy_cleanup(&alloc);
+    return 0;
+}