_REENT_CHECK_VERIFY calls __assert_func even if NDEBUG is defined

Hallo all:

I have used Newlib 3.1.0 (and older versions) for quite some time. I am trying to upgrade to the latest release/snapshot 3.3.0, but I hit a compilation error in release builds (with NDEBUG defined):

newlib-3.3.0/newlib/libc/stdlib/rand.c:78: undefined reference to `__assert_func'

I tracked it down to this definition:

/* Specify how to handle reent_check malloc failures. */
#ifdef _REENT_CHECK_VERIFY
#include <assert.h>
#define __reent_assert(x) ((x) ? (void)0 : __assert_func(__FILE__, __LINE__, (char *)0, "REENT malloc succeeded"))
#else
#define __reent_assert(x) ((void)0)
#endif

This is unfortunate. First of all, I wonder what happens if malloc fails and there is no assert. Will there be a crash?

Then, I would like to assert() in debug builds, and not in release builds. My code does not define __assert_func in release builds, because assertions are only supposed to work if NDEBUG is not defined. That has been working fine for years, until this Newlib version.

I am configuring Newlib with --disable-newlib-multithread , because my embedded firmware has no threads. But I guess I still have to deal with "struct _reent", don't I? I would have hoped that, in this single-thread situation, any reentrancy structure could be allocated statically. Or is there any way to avoid this malloc()?

Thanks in advance,
  rdiez