wxWidgets/include/wx/debug.h

/////////////////////////////////////////////////////////////////////////////
// Name:        wx/debug.h
// Purpose:     Misc debug functions and macros
// Author:      Vadim Zeitlin
// Created:     29/01/98
// RCS-ID:      $Id$
// Copyright:   (c) 1998-2009 Vadim Zeitlin <vadim@wxwidgets.org>
// Licence:     wxWindows licence
/////////////////////////////////////////////////////////////////////////////

#ifndef _WX_DEBUG_H_
#define _WX_DEBUG_H_

#if !defined(__WXPALMOS5__) && !defined(__WXWINCE__)
    #include  <assert.h>
#endif // systems without assert.h

#include <limits.h>          // for CHAR_BIT used below

#include "wx/chartype.h"     // for __TFILE__ and wxChar
#include "wx/cpp.h"          // for __WXFUNCTION__

class WXDLLIMPEXP_FWD_BASE wxString;
class WXDLLIMPEXP_FWD_BASE wxCStrData;

// ----------------------------------------------------------------------------
// Defines controlling the debugging macros
// ----------------------------------------------------------------------------

/*
    wxWidgets can be built with several different levels of debug support
    specified by the value of wxDEBUG_LEVEL constant:

    0:  No assertion macros at all, this should only be used when optimizing
        for resource-constrained systems (typically embedded ones).
    1:  Default level, most of the assertions are enabled.
    2:  Maximal (at least for now): asserts which are "expensive"
        (performance-wise) or only make sense for finding errors in wxWidgets
        itself, as opposed to bugs in applications using it, are also enabled.

    For compatibility reasons, currently wxDEBUG_LEVEL is defined if
    __WXDEBUG__ is defined but in the near future (2.9.1) the role of the flags
    will change and wxDEBUG_LEVEL will be the primary value with __WXDEBUG__
    only used for compatibility.
 */

// if _DEBUG is defined (MS VC++ and others use it in debug builds), define
// __WXDEBUG__ too
#ifdef _DEBUG
    #ifndef __WXDEBUG__
        #define __WXDEBUG__
    #endif // !__WXDEBUG__
#endif // _DEBUG

// if NDEBUG is defined (<assert.h> uses it), undef __WXDEBUG__ and WXDEBUG
#ifdef NDEBUG
    #undef __WXDEBUG__
    #undef WXDEBUG
#endif // NDEBUG

// if __WXDEBUG__ is defined, make sure that WXDEBUG is defined and >= 1
#ifdef __WXDEBUG__
    #if !defined(WXDEBUG) || !WXDEBUG
        #undef WXDEBUG
        #define WXDEBUG 1
    #endif // !WXDEBUG
#endif // __WXDEBUG__

// temporarily define wxDEBUG_LEVEL as function of __WXDEBUG__
#if !defined(wxDEBUG_LEVEL)
    #ifdef __WXDEBUG__
        #define wxDEBUG_LEVEL 1
    #else
        #define wxDEBUG_LEVEL 0
    #endif
#endif // !defined(wxDEBUG_LEVEL)

// ----------------------------------------------------------------------------
// Handling assertion failures
// ----------------------------------------------------------------------------

/*
    Type for the function called in case of assert failure, see
    wxSetAssertHandler().
 */
typedef void (*wxAssertHandler_t)(const wxString& file,
                                  int line,
                                  const wxString& func,
                                  const wxString& cond,
                                  const wxString& msg);

#if wxDEBUG_LEVEL

// the global assert handler function, if it is NULL asserts don't check their
// conditions
extern WXDLLIMPEXP_DATA_BASE(wxAssertHandler_t) wxTheAssertHandler;

/*
    Sets the function to be called in case of assertion failure.

    The default assert handler forwards to wxApp::OnAssertFailure() whose
    default behaviour is, in turn, to show the standard assertion failure
    dialog if a wxApp object exists or shows the same dialog itself directly
    otherwise.

    While usually it is enough -- and more convenient -- to just override
    OnAssertFailure(), to handle all assertion failures, including those
    occurring even before wxApp object creation or after its destruction you
    need to provide your assertion handler function.

    This function also provides a simple way to disable all asserts: simply
    pass NULL pointer to it. Doing this will result in not even evaluating
    assert conditions at all, avoiding almost all run-time cost of asserts.

    Notice that this function is not MT-safe, so you should call it before
    starting any other threads.

    The return value of this function is the previous assertion handler. It can
    be called after any pre-processing by your handler and can also be restored
    later if you uninstall your handler.
 */
inline wxAssertHandler_t wxSetAssertHandler(wxAssertHandler_t handler)
{
    const wxAssertHandler_t old = wxTheAssertHandler;
    wxTheAssertHandler = handler;
    return old;
}

#else // !wxDEBUG_LEVEL

// provide empty stubs in case assertions are completely disabled
//
// NB: can't use WXUNUSED() here as we're included from wx/defs.h before it is
//     defined
inline wxAssertHandler_t wxSetAssertHandler(wxAssertHandler_t /* handler */)
{
    return NULL;
}

#endif // wxDEBUG_LEVEL/!wxDEBUG_LEVEL

// simply a synonym for wxSetAssertHandler(NULL)
inline void wxDisableAsserts() { wxSetAssertHandler(NULL); }

#if wxDEBUG_LEVEL

/*
    wxOnAssert() is used by the debugging macros defined below. Different
    overloads are needed because these macros can be used with or without _T().

    All of them are implemented in src/common/appcmn.cpp and unconditionally
    call wxTheAssertHandler so the caller must check that it is non-NULL
    (assert macros do it).
 */

#if wxUSE_UNICODE

// these overloads are the ones typically used by debugging macros: we have to
// provide wxChar* msg version because it's common to use _T() in the macros
// and finally, we can't use const wx(char)* msg = NULL, because that would
// be ambiguous
//
// also notice that these functions can't be inline as wxString is not defined
// yet (and can't be as wxString code itself may use assertions)
extern void WXDLLIMPEXP_BASE wxOnAssert(const char *file,
                                        int line,
                                        const char *func,
                                        const char *cond);

extern void WXDLLIMPEXP_BASE wxOnAssert(const char *file,
                                        int line,
                                        const char *func,
                                        const char *cond,
                                        const char *msg);

extern void WXDLLIMPEXP_BASE wxOnAssert(const char *file,
                                        int line,
                                        const char *func,
                                        const char *cond,
                                        const wxChar *msg);
#endif /* wxUSE_UNICODE */

// this version is for compatibility with wx 2.8 Unicode build only, we don't
// use it ourselves any more except in ANSI-only build in which case it is all
// we need
extern void WXDLLIMPEXP_BASE wxOnAssert(const wxChar *file,
                                        int line,
                                        const char *func,
                                        const wxChar *cond,
                                        const wxChar *msg = NULL);

// these overloads work when msg passed to debug macro is a string and we
// also have to provide wxCStrData overload to resolve ambiguity which would
// otherwise arise from wxASSERT( s.c_str() )
extern void WXDLLIMPEXP_BASE wxOnAssert(const wxString& file,
                                        int line,
                                        const wxString& func,
                                        const wxString& cond,
                                        const wxString& msg);

extern void WXDLLIMPEXP_BASE wxOnAssert(const wxString& file,
                                        int line,
                                        const wxString& func,
                                        const wxString& cond);

extern void WXDLLIMPEXP_BASE wxOnAssert(const char *file,
                                        int line,
                                        const char *func,
                                        const char *cond,
                                        const wxCStrData& msg);

extern void WXDLLIMPEXP_BASE wxOnAssert(const char *file,
                                        int line,
                                        const char *func,
                                        const char *cond,
                                        const wxString& msg);

#endif // wxDEBUG_LEVEL


// ----------------------------------------------------------------------------
// Debugging macros
// ----------------------------------------------------------------------------

/*
    Assertion macros: check if the condition is true and call assert handler
    (which will by default notify the user about failure) if it isn't.

    wxASSERT and wxFAIL macros as well as wxTrap() function do nothing at all
    if wxDEBUG_LEVEL is 0 however they do check their conditions at default
    debug level 1, unlike the previous wxWidgets versions.

    wxASSERT_LEVEL_2 is meant to be used for "expensive" asserts which should
    normally be disabled because they have a big impact on performance and so
    this macro only does anything if wxDEBUG_LEVEL >= 2.
 */
#if wxDEBUG_LEVEL
    // call this function to break into the debugger unconditionally (assuming
    // the program is running under debugger, of course)
    extern void WXDLLIMPEXP_BASE wxTrap();

    // assert checks if the condition is true and calls the assert handler with
    // the provided message if it isn't
    //
    // NB: the macro is defined like this to ensure that nested if/else
    //     statements containing it are compiled in the same way whether it is
    //     defined as empty or not; also notice that we can't use ";" instead
    //     of "{}" as some compilers warn about "possible unwanted ;" then
    #define wxASSERT_MSG(cond, msg)                                           \
        if ( !wxTheAssertHandler || (cond) )                                  \
        {}                                                                    \
        else                                                                  \
            wxOnAssert(__FILE__, __LINE__, __WXFUNCTION__, #cond, msg)

    // a version without any additional message, don't use unless condition
    // itself is fully self-explanatory
    #define wxASSERT(cond) wxASSERT_MSG(cond, (const char*)NULL)

    // wxFAIL is a special form of assert: it always triggers (and so is
    // usually used in normally unreachable code)
    #define wxFAIL_COND_MSG(cond, msg) \
        if ( !wxTheAssertHandler )                                            \
        {}                                                                    \
        else                                                                  \
            wxOnAssert(__FILE__, __LINE__,  __WXFUNCTION__, cond, msg)
    #define wxFAIL_MSG(msg) wxFAIL_COND_MSG("Assert failure", msg)
    #define wxFAIL wxFAIL_MSG((const char*)NULL)
#else // !wxDEBUG_LEVEL
    #define wxTrap()

    #define wxASSERT(cond)
    #define wxASSERT_MSG(cond, msg)
    #define wxFAIL
    #define wxFAIL_MSG(msg)
    #define wxFAIL_COND_MSG(cond, msg)
#endif  // wxDEBUG_LEVEL

#if wxDEBUG_LEVEL >= 2
    #define wxASSERT_LEVEL_2_MSG(cond, msg) wxASSERT_MSG(cond, msg)
    #define wxASSERT_LEVEL_2(cond) wxASSERT(cond)
#else // wxDEBUG_LEVEL < 2
    #define wxASSERT_LEVEL_2_MSG(cond, msg)
    #define wxASSERT_LEVEL_2(cond)
#endif


/*
    wxCHECK macros always check their conditions, setting debug level to 0 only
    makes them silent in case of failure, otherwise -- including at default
    debug level 1 -- they call the assert handler if the condition is false

    They are supposed to be used only in invalid situation: for example, an
    invalid parameter (e.g. a NULL pointer) is passed to a function. Instead of
    dereferencing it and causing core dump the function might use

        wxCHECK_RET( p != NULL, "pointer can't be NULL" )
*/

// the generic macro: takes the condition to check, the statement to be execute
// in case the condition is false and the message to pass to the assert handler
#define wxCHECK2_MSG(cond, op, msg)                                       \
    if ( cond )                                                           \
    {}                                                                    \
    else                                                                  \
    {                                                                     \
        wxFAIL_COND_MSG(#cond, msg);                                      \
        op;                                                               \
    }                                                                     \
    struct wxDummyCheckStruct /* just to force a semicolon */

// check which returns with the specified return code if the condition fails
#define wxCHECK_MSG(cond, rc, msg)   wxCHECK2_MSG(cond, return rc, msg)

// check that expression is true, "return" if not (also FAILs in debug mode)
#define wxCHECK(cond, rc)            wxCHECK_MSG(cond, rc, (const char*)NULL)

// check that expression is true, perform op if not
#define wxCHECK2(cond, op)           wxCHECK2_MSG(cond, op, (const char*)NULL)

// special form of wxCHECK2: as wxCHECK, but for use in void functions
//
// NB: there is only one form (with msg parameter) and it's intentional:
//     there is no other way to tell the caller what exactly went wrong
//     from the void function (of course, the function shouldn't be void
//     to begin with...)
#define wxCHECK_RET(cond, msg)       wxCHECK2_MSG(cond, return, msg)


// ----------------------------------------------------------------------------
// Compile time asserts
//
// Unlike the normal assert and related macros above which are checked during
// the program run-time the macros below will result in a compilation error if
// the condition they check is false. This is usually used to check the
// expressions containing sizeof()s which cannot be tested with the
// preprocessor. If you can use the #if's, do use them as you can give a more
// detailed error message then.
// ----------------------------------------------------------------------------

/*
  How this works (you don't have to understand it to be able to use the
  macros): we rely on the fact that it is invalid to define a named bit field
  in a struct of width 0. All the rest are just the hacks to minimize the
  possibility of the compiler warnings when compiling this macro: in
  particular, this is why we define a struct and not an object (which would
  result in a warning about unused variable) and a named struct (otherwise we'd
  get a warning about an unnamed struct not used to define an object!).
 */

#define wxMAKE_UNIQUE_ASSERT_NAME           wxMAKE_UNIQUE_NAME(wxAssert_)

/*
  The second argument of this macro must be a valid C++ identifier and not a
  string. I.e. you should use it like this:

    wxCOMPILE_TIME_ASSERT( sizeof(int) >= 2, YourIntsAreTooSmall );

 It may be used both within a function and in the global scope.
*/
#if defined(__WATCOMC__)
    /* avoid "unused symbol" warning */
    #define wxCOMPILE_TIME_ASSERT(expr, msg) \
        class wxMAKE_UNIQUE_ASSERT_NAME { \
          unsigned int msg: expr; \
          wxMAKE_UNIQUE_ASSERT_NAME() { wxUnusedVar(msg); } \
        }
#else
    #define wxCOMPILE_TIME_ASSERT(expr, msg) \
        struct wxMAKE_UNIQUE_ASSERT_NAME { unsigned int msg: expr; }
#endif

/*
   When using VC++ 6 with "Edit and Continue" on, the compiler completely
   mishandles __LINE__ and so wxCOMPILE_TIME_ASSERT() doesn't work, provide a
   way to make "unique" assert names by specifying a unique prefix explicitly
 */
#define wxMAKE_UNIQUE_ASSERT_NAME2(text) wxCONCAT(wxAssert_, text)

#define wxCOMPILE_TIME_ASSERT2(expr, msg, text) \
    struct wxMAKE_UNIQUE_ASSERT_NAME2(text) { unsigned int msg: expr; }

// helpers for wxCOMPILE_TIME_ASSERT below, for private use only
#define wxMAKE_BITSIZE_MSG(type, size) type ## SmallerThan ## size ## Bits

// a special case of compile time assert: check that the size of the given type
// is at least the given number of bits
#define wxASSERT_MIN_BITSIZE(type, size) \
    wxCOMPILE_TIME_ASSERT(sizeof(type) * CHAR_BIT >= size, \
                          wxMAKE_BITSIZE_MSG(type, size))


// ----------------------------------------------------------------------------
// other miscellaneous debugger-related functions
// ----------------------------------------------------------------------------

/*
    Return true if we're running under debugger.

    Currently this only really works under Win32 and Mac in CodeWarrior builds,
    it always returns false in other cases.
 */
#if defined(__WXMAC__) || defined(__WIN32__)
    extern bool WXDLLIMPEXP_BASE wxIsDebuggerRunning();
#else // !Mac
    inline bool wxIsDebuggerRunning() { return false; }
#endif // Mac/!Mac

// An assert helper used to avoid warning when testing constant expressions,
// i.e. wxASSERT( sizeof(int) == 4 ) can generate a compiler warning about
// expression being always true, but not using
// wxASSERT( wxAssertIsEqual(sizeof(int), 4) )
//
// NB: this is made obsolete by wxCOMPILE_TIME_ASSERT() and should no
//     longer be used.
extern bool WXDLLIMPEXP_BASE wxAssertIsEqual(int x, int y);

// Use of wxFalse instead of false suppresses compiler warnings about testing
// constant expression
extern WXDLLIMPEXP_DATA_BASE(const bool) wxFalse;

#define wxAssertFailure wxFalse

// This is similar to WXUNUSED() and useful for parameters which are only used
// in assertions.
#if wxDEBUG_LEVEL
    #define WXUNUSED_UNLESS_DEBUG(param)  param
#else
    #define WXUNUSED_UNLESS_DEBUG(param)  WXUNUSED(param)
#endif


#endif // _WX_DEBUG_H_