Hook probe capability

Macros
#define	APR_HOOK_INT_DCL_UD
#define	APR_HOOK_PROBE_ENTRY(ud, ns, name, args)
#define	APR_HOOK_PROBE_RETURN(ud, ns, name, rv, args)
#define	APR_HOOK_PROBE_INVOKE(ud, ns, name, src, args)
#define	APR_HOOK_PROBE_COMPLETE(ud, ns, name, src, rv, args)

Detailed Description

APR hooks provide a trace probe capability for capturing the flow of control and return values with hooks.

In order to use this facility, the application must define the symbol APR_HOOK_PROBES_ENABLED and the four APR_HOOK_PROBE_ macros described below before including apr_hooks.h in files that use the APR_IMPLEMENT_EXTERNAL_HOOK_* macros.

This probe facility is not provided for APR optional hooks.

Macro Definition Documentation

#define APR_HOOK_INT_DCL_UD

internal implementation detail to avoid the ud declaration when hook probes are not used

#define APR_HOOK_PROBE_COMPLETE	(		ud,
			ns,
			name,
			src,
			rv,
			args
	)

User-defined hook probe macro that is invoked after calling a hook function.

Parameters

ud	A void * user data field that was filled in by the user- provided APR_HOOK_PROBE_ENTRY().
ns	The namespace prefix of the hook functions
name	The name of the hook
src	The value of apr_hook_debug_current at the time the function was hooked (usually the source file implementing the hook function).
rv	The return value of the hook function, or 0 if the hook is void.
args	The argument list to the hook functions, with enclosing parens.

#define APR_HOOK_PROBE_ENTRY	(		ud,
			ns,
			name,
			args
	)

User-defined hook probe macro that is invoked when the hook is run, before calling any hook functions.

Parameters

ud	A void * user data field that should be filled in by this macro, and will be provided to the other hook probe macros.
ns	The namespace prefix of the hook functions
name	The name of the hook
args	The argument list to the hook functions, with enclosing parens.

#define APR_HOOK_PROBE_INVOKE	(		ud,
			ns,
			name,
			src,
			args
	)

User-defined hook probe macro that is invoked before calling a hook function.

Parameters

ud	A void * user data field that was filled in by the user- provided APR_HOOK_PROBE_ENTRY().
ns	The namespace prefix of the hook functions
name	The name of the hook
src	The value of apr_hook_debug_current at the time the function was hooked (usually the source file implementing the hook function).
args	The argument list to the hook functions, with enclosing parens.

#define APR_HOOK_PROBE_RETURN	(		ud,
			ns,
			name,
			rv,
			args
	)

User-defined hook probe macro that is invoked after the hook has run.

Parameters

ud	A void * user data field that was filled in by the user- provided APR_HOOK_PROBE_ENTRY().
ns	The namespace prefix of the hook functions
name	The name of the hook
rv	The return value of the hook, or 0 if the hook is void.
args	The argument list to the hook functions, with enclosing parens.