| _DIAGASSERT(3) | Library Functions Manual | _DIAGASSERT(3) | 
_DIAGASSERT —
#include <assert.h>
_DIAGASSERT(expression);
_DIAGASSERT() macro tests the given
  expression and if it is false, one or more of the
  following may occur:
stderr
      stream.This behaviour may be changed by setting the
    LIBC_DIAGASSERT environment variable (see
  below).
The diagnostic message consists of the text of the expression, the name of the source file, the line number and the enclosing function.
If expression is true, the
    _DIAGASSERT() macro does nothing.
The _DIAGASSERT() macro is not compiled in
    by default, and will only be compiled in with the
    cc(1) option
    -D_DIAGNOSTIC.
This macro is used in the various system libraries such as the Standard C Library (libc, -lc) to ensure that various library calls are invoked with valid arguments.
LIBC_DIAGASSERT environment variable can be used to
  modify the default behaviour of logging the assertion to the system logger.
LIBC_DIAGASSERT may be set to one or more
    of the following characters:
"assertion \"%s\" failed: file \"%s\", line %d, function \"%s\"\n", "expression", __FILE__, __LINE__, __func__
_DIAGASSERT macro appeared in
  NetBSD 1.5.
| January 22, 2007 | NetBSD 9.3 |