0ad/source/lib/debug.h

// platform-independent debug interface
// Copyright (c) 2002-2005 Jan Wassenberg
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 2 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// Contact info:
//   Jan.Wassenberg@stud.uni-karlsruhe.de
//   http://www.stud.uni-karlsruhe.de/~urkt/

#ifndef DEBUG_H_INCLUDED
#define DEBUG_H_INCLUDED

#include "lib.h" // STMT
#include "sysdep/sysdep.h"		// ErrorReaction
#if OS_WIN
# include "sysdep/win/wdbg.h"
#else
# include "sysdep/unix/udbg.h"
#endif

/*

[KEEP IN SYNC WITH WIKI]

overview
--------

this module provides platform-independent debug facilities, useful for
diagnosing and reporting program errors.
- a symbol engine provides access to compiler-generated debug information and
  can also give a stack trace including local variables;
- the breakpoint API enables stopping when a given address is
  executed, read or written to (as specified);
- a hook into the system's memory allocator can optionally check for and
  report heap corruption;
- our more powerful assert() replacement gives a stack trace so
  that the underlying problem becomes apparent;
- the output routines make for platform-independent logging and
  crashlogs with "last-known activity" reporting.


usage
-----

please see the detailed comments below on how to use the individual features.
much of this is only helpful if you explicity ask for it!


rationale
---------

much of this functionality already exists within the VC7 IDE/debugger.
motivation for this code is as follows:
- we want a consistent interface for all platforms;
- limitations(*) in the VC variants should be fixed;
- make debugging as easy as possible.

* mostly pertaining to Release mode - e.g. symbols cannot be resolved
even if debug information is present and assert dialogs are useless.

*/

//-----------------------------------------------------------------------------
// debug memory allocator
//-----------------------------------------------------------------------------

// check heap integrity (independently of mmgr).
// errors are reported by the CRT or via display_error.
extern void debug_heap_check(void);

enum DebugHeapChecks
{
	// no automatic checks. (default)
	DEBUG_HEAP_NONE   = 0,

	// basic automatic checks when deallocating.
	DEBUG_HEAP_NORMAL = 1,

	// all automatic checks on every memory API call. this is really
	// slow (x100), but reports errors closer to where they occurred.
	DEBUG_HEAP_ALL    = 2
};

// call at any time; from then on, the specified checks will be performed.
// if not called, the default is DEBUG_HEAP_NONE, i.e. do nothing.
extern void debug_heap_enable(DebugHeapChecks what);


//-----------------------------------------------------------------------------
// debug_assert
//-----------------------------------------------------------------------------

// rationale: we call this "debug_assert" instead of "assert" for the
// following reasons:
// - consistency (everything here is prefixed with debug_) and
// - to avoid inadvertent use of the much less helpful built-in CRT assert.
//   if we were to override assert, it would be difficult to tell whether
//   user source has included <assert.h> (possibly indirectly via other
//   headers) and thereby stomped on our definition.

// make sure the expression <expr> evaluates to non-zero. used to validate
// invariants in the program during development and thus gives a
// very helpful warning if something isn't going as expected.
// sprinkle these liberally throughout your code!
//
// recommended use is debug_assert(expression && "descriptive string") -
// the string can pass more information about the problem on to whomever
// is seeing the error.
//
// rationale: 0x55 and 0xAA are distinctive values and thus
// help debug the symbol engine.
#define debug_assert(expr) \
STMT(\
	static unsigned char suppress__ = 0x55;\
	if(suppress__ == 0x55 && !(expr))\
	{\
		switch(debug_assert_failed(__FILE__, __LINE__, __func__, #expr))\
		{\
		case ER_SUPPRESS:\
			suppress__ = 0xAA;\
			break;\
		case ER_CONTINUE:\
			break;\
		default:\
		case ER_BREAK:\
			debug_break();\
			break;\
		}\
	}\
)

// called when an assertion has failed; notifies the user via display_error.
extern enum ErrorReaction debug_assert_failed(const char* file, int line,
	const char* func, const char* assert_expr);

// show a dialog to make sure unexpected states in the program are noticed.
// this is less error-prone than "debug_assert(0 && "text");" and avoids
// "conditional expression is constant" warnings. we'd really like to
// completely eliminate the problem; replacing 0 literals with extern
// volatile variables fools VC7 but isn't guaranteed to be free of overhead.
// we therefore just squelch the warning (unfortunately non-portable).
#define debug_warn(str) debug_assert((str) && 0)


#define DEBUG_WARN_ERR(err) \
STMT(\
	static unsigned char suppress__ = 0x55;\
	if(suppress__ == 0x55)\
	{\
		switch(debug_warn_err(err, __FILE__, __LINE__, __func__))\
		{\
		case ER_SUPPRESS:\
			suppress__ = 0xAA;\
			break;\
		case ER_CONTINUE:\
			break;\
		default:\
		case ER_BREAK:\
			debug_break();\
			break;\
		}\
	}\
)

extern enum ErrorReaction debug_warn_err(int err, const char* file, int line,
	const char* func);


//-----------------------------------------------------------------------------
// logging
//-----------------------------------------------------------------------------

// write a formatted string to the debug channel, subject to filtering
// (see below). implemented via debug_puts - see performance note there.
extern void debug_printf(const char* fmt, ...);
// note: this merely converts to a MBS and calls debug_printf.
extern void debug_wprintf(const wchar_t* fmt, ...);


//
// filtering
//

// debug output is very useful, but "too much of a good thing can kill you".
// we don't want to require different LOGn() macros that are enabled
// depending on "debug level", because changing that entails lengthy
// compiles and it's too coarse-grained. instead, we require all
// strings to start with "tag_string:" (exact case and no quotes;
// the alphanumeric-only <tag_string> identifies output type).
// they are then subject to filtering: only if the tag has been
// "added" via debug_filter_add is the appendant string displayed.
//
// this approach is easiest to implement and is fine because we control
// all logging code. LIMODS falls from consideration since it's not
// portable and too complex.
//
// notes:
// - filter changes only affect subsequent debug_*printf calls;
//   output that didn't pass the filter is permanently discarded.
// - strings not starting with a tag are always displayed.
// - debug_filter_* can be called at any time and from the debugger.

// in future, allow output with the given tag to proceed.
// no effect if already added.
extern void debug_filter_add(const char* tag);
// in future, discard output with the given tag.
// no effect if not currently added.
extern void debug_filter_remove(const char* tag);
// clear all filter state; equivalent to debug_filter_remove for
// each tag that was debug_filter_add-ed.
extern void debug_filter_clear();


// write to memory buffer (fast)
// used for "last activity" reporting in the crashlog.
extern void debug_wprintf_mem(const wchar_t* fmt, ...);

// write all logs and <text> out to crashlog.txt (unicode format).
extern int debug_write_crashlog(const wchar_t* text);


//-----------------------------------------------------------------------------
// breakpoints
//-----------------------------------------------------------------------------

// trigger a breakpoint when reached/"called".
// defined as a macro by the platform-specific header above; this allows
// breaking directly into the target function, instead of one frame
// below it as with a conventional call-based implementation.
//#define debug_break()


// sometimes mmgr's 'fences' (making sure padding before and after the
// allocation remains intact) aren't enough to catch hard-to-find
// memory corruption bugs. another tool is to trigger a debug exception
// when the later to be corrupted variable is accessed; the problem should
// then become apparent.
// the VC++ IDE provides such 'breakpoints', but can only detect write access.
// additionally, it can't resolve symbols in Release mode (where this would
// be most useful), so we provide a breakpoint API.

// (values chosen to match IA-32 bit defs, so compiler can optimize.
// this isn't required, it'll work regardless.)
enum DbgBreakType
{
	DBG_BREAK_CODE       = 0,	// execute
	DBG_BREAK_DATA_WRITE = 1,	// write
	DBG_BREAK_DATA       = 3	// read or write
};

// arrange for a debug exception to be raised when <addr> is accessed
// according to <type>.
// for simplicity, the length (range of bytes to be checked) is derived
// from addr's alignment, and is typically 1 machine word.
// breakpoints are a limited resource (4 on IA-32); if none are
// available, we return ERR_LIMIT.
extern int debug_set_break(void* addr, DbgBreakType type);

// remove all breakpoints that were set by debug_set_break.
// important, since these are a limited resource.
extern int debug_remove_all_breaks();


//-----------------------------------------------------------------------------
// symbol access
//-----------------------------------------------------------------------------

// maximum number of characters (including trailing \0) written to
// user's buffers by debug_resolve_symbol.
const size_t DBG_SYMBOL_LEN = 1000;
const size_t DBG_FILE_LEN = 100;

// read and return symbol information for the given address. all of the
// output parameters are optional; we pass back as much information as is
// available and desired. return 0 iff any information was successfully
// retrieved and stored.
// sym_name and file must hold at least the number of chars above;
// file is the base name only, not path (see rationale in wdbg_sym).
// the PDB implementation is rather slow (~500us).
extern int debug_resolve_symbol(void* ptr_of_interest, char* sym_name, char* file, int* line);

// write a complete stack trace (including values of local variables) into
// the specified buffer. if <context> is nonzero, it is assumed to be a
// platform-specific representation of execution state (e.g. Win32 CONTEXT)
// and tracing starts there; this is useful for exceptions.
// otherwise, tracing starts at the current stack position, and the given
// number of stack frames (i.e. functions) above the caller are skipped.
// this prevents functions like debug_assert_failed from
// cluttering up the trace. returns the buffer for convenience.
extern const wchar_t* debug_dump_stack(wchar_t* buf, size_t max_chars, uint skip, void* context);


//-----------------------------------------------------------------------------
// helper functions (used by implementation)
//-----------------------------------------------------------------------------

// [system-dependent] write a string to the debug channel.
// this can be quite slow (~1 ms)! On Windows, it uses OutputDebugString
// (entails context switch), otherwise stdout+fflush (waits for IO).
extern void debug_puts(const char* text);

// abstraction of all STL iterators used by debug_stl.
typedef const u8* (*DebugIterator)(void* internal, size_t el_size);

// return address of the Nth function on the call stack.
// if <context> is nonzero, it is assumed to be a platform-specific
// representation of execution state (e.g. Win32 CONTEXT) and tracing
// starts there; this is useful for exceptions.
// otherwise, tracing starts at the current stack position, and the given
// number of stack frames (i.e. functions) above the caller are skipped.
// used by mmgr to determine what function requested each allocation;
// this is fast enough to allow that.
extern void* debug_get_nth_caller(uint skip, void* context);

// return 1 if the pointer appears to be totally bogus, otherwise 0.
// this check is not authoritative (the pointer may be "valid" but incorrect)
// but can be used to filter out obviously wrong values in a portable manner.
extern int debug_is_pointer_bogus(const void* p);

extern bool debug_is_code_ptr(void* p);
extern bool debug_is_stack_ptr(void* p);


// set the current thread's name; it will be returned by subsequent calls to
// debug_get_thread_name.
//
// the string pointed to by <name> MUST remain valid throughout the
// entire program; best to pass a string literal. allocating a copy
// would be quite a bit more work due to cleanup issues.
//
// if supported on this platform, the debugger is notified of the new name;
// it will be displayed there instead of just the handle.
extern void debug_set_thread_name(const char* name);

// return the pointer assigned by debug_set_thread_name or 0 if
// that hasn't been done yet for this thread.
extern const char* debug_get_thread_name();


// call at exit to avoid leaks (not strictly necessary).
extern void debug_shutdown();

#endif	// #ifndef DEBUG_H_INCLUDED