Component bsla_used [Package bsla]

Provide a macro to prevent elision of unused entities. More...

Outline

• Purpose
• Macros
• Description
  • Macro Reference
  • Usage
    • Example 1: Unused Variables
    • Example 2: Unused Functions

Purpose:

Provide a macro to prevent elision of unused entities.

Macros:

BSLA_USED	emit annotated entity even if not referenced
BSLA_USED_IS_ACTIVE	0 if BSLA_USED expands to nothing and 1 otherwise

See also:

Component bsla_annotations

Description:

This component provides a preprocessor macro that will guarantee the emission of a local function, type, or variable whether it is used or not.

Macro Reference:

BSLA_USED:
This annotation indicates that the so-annotated function, variable, or type must be emitted even if it appears that it is not referenced.

BSLA_USED_IS_ACTIVE:
The macro BSLA_USED_IS_ACTIVE is defined to 0 if BSLA_USED expands to nothing and 1 otherwise.

Usage:

This section illustrates intended use of this component.

Example 1: Unused Variables:

First, we declare two unused static variables, one marked BSLA_UNUSED and the other marked BSLA_USED:

  static
  int usage_UNUSED_variable_no_warning BSLA_UNUSED;

  static
  int usage_USED_variable_no_warning BSLA_USED;

Finally, if we compile with clang and go into the debugger and stop in main, which is in the same file and from which both variables are visible, we observe that the variable marked BSLA_UNUSED cannot be accessed, but the variable marked BSLA_USED can.

Example 2: Unused Functions:

First, declare two unused static functions, one marked BSLA_UNUSED and one marked BSLA_USED:

  static
  void usage_UNUSED_function_no_warning(int woof) BSLA_UNUSED;
      // Print the specified 'woof'.
  static
  void usage_UNUSED_function_no_warning(int woof)
  {
      printf("%d\n", woof);
  }

  static
  void usage_USED_function_no_warning(int woof) BSLA_USED;
      // Print the specified 'woof'.
  static
  void usage_USED_function_no_warning(int woof)
  {
      printf("%d\n", woof);
  }

Finally, if we compile with clang and go into the debugger, we find that we can put a breakpoint in the function marked BSLA_USED, but not in the function marked BSLA_UNUSED.