Valgrind vararg error

.gitignore

*.c
*.o
*.a
vafail

Makefile

# this has been tested with gcc-4.8, clang-3.8, clang-7, clang-9 and clang-10
CC=clang-7
CFLAGS=-g

fail: all
	${CC} -dumpversion
	valgrind ./vafail

all: libvafail.a vafail

.c.o:
	${CC} ${CFLAGS} -c $< -o $@

libvafail.a: va_test_fun.o
	$(AR) $(ARFLAGS) $@ $<

vafail: vafail.o libvafail.a
	${CC} ${CFLAGS} $^ -o $@

clean:
	rm *.o *.a vafail

va_test_fun.c

#include <stdarg.h>
#include <stddef.h>
#include <valgrind/memcheck.h>

void va_test_fun(int i, unsigned char *pc, unsigned long *pl, const unsigned char *p, unsigned long l, ...)
{
   va_list              args;
   const unsigned char *curptr;
   unsigned long        curlen;

   va_start(args, l);
   curptr = p;
   curlen = l;
   for (;;) {
      VALGRIND_CHECK_VALUE_IS_DEFINED(curptr);
      VALGRIND_CHECK_VALUE_IS_DEFINED(curlen);
      VALGRIND_CHECK_MEM_IS_DEFINED(curptr, curlen);
      /* step to next */
      curptr = va_arg(args, const unsigned char*);
      if (curptr == NULL) {
         break;
      }
      curlen = va_arg(args, unsigned long);
   }
}

vafail.c

#include <stddef.h>

void va_test_fun(int i, unsigned char *pc, unsigned long *pl, const unsigned char *p, unsigned long l, ...);

int main(void)
{
	unsigned long l = 123;
	unsigned char buf[1024] = {0};
	va_test_fun(100, buf, &l, buf, l, buf, 4, NULL, 0);
	return 0;
}