tralloc

commit 6673b3b3ca47c805b8a6966bd9ae6e09636a34ca
parent bbf4640c55b73b8c24eb4c5e8a98b8aad841acca
Author: gearsix <gearsix@tuta.io>
Date:   Fri, 26 Aug 2022 15:37:02 +0100

added original-draft.c

Diffstat:
A
original-draft.c
 | 
56
++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 56 insertions(+), 0 deletions(-)
diff --git a/original-draft.c b/original-draft.c
@@ -0,0 +1,56 @@
+/* htrack.c
+ * example of how to track heap-heapsiz during runtime
+ * -gearsix
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static size_t heapsiz = 0;
+
+// mallocw (malloc wrapper) allocates nbytes + sizeof(size_t).
+// the allocated number of bytes for the pointer is stored in [0],
+// the memory block requested by the user is stored from [1]..[n].
+// note that ptr[1] is returned.
+void *mallocw(size_t nbytes)
+{
+	nbytes += sizeof(size_t);
+	heapsiz += nbytes;
+	size_t *ptr = malloc(nbytes);
+	ptr[0] = nbytes;
+	return &ptr[1];
+}
+
+// sizeofw (sizeof wrapper) check [-1] for the size_t value set by
+// mallocw. ptr must have been allocated by mallocw to avoid issues.
+size_t sizeofw(void *ptr)
+{
+	return ((size_t *)ptr)[-1];
+}
+
+// freew (free wrapper) frees *ptr from [-1], will probably cause
+// an issue if the ptr wasn't allocated by mallocw.
+void freew(void *ptr)
+{
+	heapsiz -= sizeofw(ptr);
+	free((size_t *)ptr-1);
+}
+
+int main(int argc, char *argv[])
+{
+	printf("heapsiz: %lu\n", heapsiz);
+
+	char *str = mallocw(6);
+	if (str == NULL) {
+		fprintf(stderr, "mallocw failed");
+		return EXIT_FAILURE;
+	}
+	strcpy(str, "foobar");
+	printf("str = '%s', strlen %d, sizeof %d\n", str, strlen(str), sizeofw(str));
+	printf("heapsiz: %lu\n", heapsiz);
+	puts("freeing str...");
+	freew(str);
+	printf("heapsiz: %lu\n", heapsiz);
+
+	return EXIT_SUCCESS;
+}