_DIAGASSERT(3) | Library Functions Manual | _DIAGASSERT(3)

# NAME

`_DIAGASSERT` —
expression verification macro

# SYNOPSIS

`#include <assert.h>`

`_DIAGASSERT`(expression);

# DESCRIPTION

The `_DIAGASSERT`() macro tests the given expression and if it is false, one or more of the following may occur:

- a diagnostic message may be logged to the system logger with syslog(3). This is default behaviour.
- a diagnostic message may be printed to the `stderr` stream.
- the calling process will be terminated by calling abort(3).

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.

# ENVIRONMENT

The `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:

a
  abort(3) once any assertion messages have been logged and/or printed.
A
  Opposite of “a”.
e
  Print the assertion message to the `stderr` stream.
E
  Opposite of “e”.
l
  Log the assertion message with syslog(3) to the facility `user.debug`.
L
  Opposite of “l”.

# DIAGNOSTICS

The diagnostic message has the following format:

    "assertion \"%s\" failed: file \"%s\", line %d, function \"%s\"\n",
    	    "expression", __FILE__, __LINE__, __func__

# SEE ALSO

cc(1), abort(3), assert(3), syslog(3)

# HISTORY

The `_DIAGASSERT` macro appeared in NetBSD 1.5.

January 22, 2007 | NetBSD 9.0