Add test program for valgrind.

tests/hellovalgrind/.gitignore

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+hellovalgrind

tests/hellovalgrind/Makefile

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+.PHONY: all
+all: hellovalgrind
+
+hellovalgrind: hellovalgrind.c
+	gcc -g -o hellovalgrind hellovalgrind.c
+
+.PHONY: clean
+clean:
+	rm -f hellovalgrind hellovalgrind.o
+

tests/hellovalgrind/hellovalgrind.c

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+#include <stdio.h>
+#include <stdlib.h>
+
+// https://developers.redhat.com/articles/2021/11/01/debug-memory-errors-valgrind-and-gdb#using_valgrind_and_gdb_together
+
+typedef struct foo {
+    int flag1;
+    int flag2;
+    int size;
+    int **buf;
+} foo;
+
+void print_buf(struct foo *s)
+{
+
+   printf("buf[0][0]: %d\n", s->buf[0][0]);
+   free(s->buf);
+}
+
+void setup_foo(struct foo *s)
+{
+    s->flag2 = 2;
+    s->buf = malloc(20 * sizeof(int));
+    for (int i = 0; i < 20; i++)
+        s->buf[i] = malloc(20 * sizeof(int));
+}
+
+int main(void)
+{
+   struct foo s;
+
+   setup_foo(&s);
+   print_buf(&s);
+
+   if (s.flag1 || s.flag2)
+       printf("hey\n");
+
+   return 0;
+}
+