debug.h

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/* Copyright (c) 2015 Wildfire Games
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/*
 * platform-independent debug support code.
 */

#ifndef INCLUDED_DEBUG
#define INCLUDED_DEBUG

// 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;
// - 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.

#include "lib/lib_api.h"
#include "lib/types.h"  // intptr_t
#include "lib/status.h"
#include "lib/alignment.h"
#include "lib/code_annotation.h"
#include "lib/code_generation.h"

/**
 * trigger a breakpoint when reached/"called".
 * if defined as a macro, the debugger can break directly into the
 * target function instead of one frame below it as with a conventional
 * call-based implementation.
 **/
#if MSC_VERSION
# define debug_break __debugbreak   // intrinsic "function"
#else
extern void debug_break();
#endif


//-----------------------------------------------------------------------------
// output
//-----------------------------------------------------------------------------

/**
 * write a formatted string to the debug channel, subject to filtering
 * (see below). implemented via debug_puts - see performance note there.
 *
 * @param fmt Format string and varargs; see printf.
 **/
LIB_API void debug_printf(const char* fmt, ...) PRINTF_ARGS(1);


/**
 * translates and displays the given strings in a dialog.
 * this is typically only used when debug_DisplayError has failed or
 * is unavailable because that function is much more capable.
 * implemented via sys_display_msg; see documentation there.
 **/
LIB_API void debug_DisplayMessage(const wchar_t* caption, const wchar_t* msg);

/// flags to customize debug_DisplayError behavior
enum DebugDisplayErrorFlags
{
    /**
     * disallow the Continue button. used e.g. if an exception is fatal.
     **/
    DE_NO_CONTINUE = 1,

    /**
     * enable the Suppress button. set automatically by debug_DisplayError if
     * it receives a non-NULL suppress pointer. a flag is necessary because
     * the sys_display_error interface doesn't get that pointer.
     * rationale for automatic setting: this may prevent someone from
     * forgetting to specify it, and disabling Suppress despite having
     * passed a non-NULL pointer doesn't make much sense.
     **/
    DE_ALLOW_SUPPRESS = 2,

    /**
     * do not trigger a breakpoint inside debug_DisplayError; caller
     * will take care of this if ER_BREAK is returned. this is so that the
     * debugger can jump directly into the offending function.
     **/
    DE_MANUAL_BREAK = 4,

    /**
     * display just the given message; do not add any information about the
     * call stack, do not write crashlogs, etc.
     */
    DE_NO_DEBUG_INFO = 8
};

/**
 * a bool that is reasonably certain to be set atomically.
 * we cannot assume support for OpenMP (requires GCC 4.2) or C++0x,
 * so we'll have to resort to intptr_t, cpu_CAS and COMPILER_FENCE.
 **/
typedef volatile intptr_t atomic_bool;

/**
 * value for suppress flag once set by debug_DisplayError.
 * rationale: this value is fairly distinctive and helps when
 * debugging the symbol engine.
 * use 0 as the initial value to avoid allocating .rdata space.
 **/
static const atomic_bool DEBUG_SUPPRESS = 0xAB;

/**
 * choices offered by the error dialog that are returned
 * by debug_DisplayError.
 **/
enum ErrorReaction
{
    /**
     * ignore, continue as if nothing happened.
     * note: value doesn't start at 0 because that is interpreted as a
     * DialogBoxParam failure.
     **/
    ER_CONTINUE = 1,

    /**
     * trigger breakpoint, i.e. enter debugger.
     * only returned if DE_MANUAL_BREAK was passed; otherwise,
     * debug_DisplayError will trigger a breakpoint itself.
     **/
    ER_BREAK
};

/**
 * all choices offered by the error dialog. those not defined in
 * ErrorReaction are acted upon by debug_DisplayError and
 * never returned to callers.
 * (this separation avoids enumerator-not-handled warnings)
 **/
enum ErrorReactionInternal
{
    ERI_CONTINUE = ER_CONTINUE,
    ERI_BREAK = ER_BREAK,

    /**
     * ignore and do not report again.
     * note: non-persistent; only applicable during this program run.
     **/
    ERI_SUPPRESS,

    /**
     * exit the program immediately.
     **/
    ERI_EXIT,

    /**
     * special return value for the display_error app hook stub to indicate
     * that it has done nothing and that the normal sys_display_error
     * implementation should be called instead.
     **/
    ERI_NOT_IMPLEMENTED
};


/**
 * display an error dialog with a message and stack trace.
 *
 * @param description text to show.
 * @param flags: see DebugDisplayErrorFlags.
 * @param context, lastFuncToSkip: see debug_DumpStack.
 * @param file, line, func: location of the error (typically passed as
 * WIDEN(__FILE__), __LINE__, __func__ from a macro)
 * @param suppress pointer to a caller-allocated flag that can be used to
 * suppress this error. if NULL, this functionality is skipped and the
 * "Suppress" dialog button will be disabled.
 * note: this flag is read and written exclusively here; caller only
 * provides the storage. values: see DEBUG_SUPPRESS above.
 * @return ErrorReaction (user's choice: continue running or stop?)
 **/
LIB_API ErrorReaction debug_DisplayError(const wchar_t* description, size_t flags, void* context, const wchar_t* lastFuncToSkip, const wchar_t* file, int line, const char* func, atomic_bool* suppress);

// simplified version for just displaying an error message
#define DEBUG_DISPLAY_ERROR(description)\
    do\
    {\
        CACHE_ALIGNED(u8) context[DEBUG_CONTEXT_SIZE];\
        (void)debug_CaptureContext(context);\
        (void)debug_DisplayError(description, 0, context, L"debug_DisplayError", WIDEN(__FILE__), __LINE__, __func__, 0);\
    }\
    while(0)


//
// 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,
 *   but are not reentrant.
 *
 * in future, allow output with the given tag to proceed.
 * no effect if already added.
 **/
LIB_API void debug_filter_add(const char* tag);

/**
 * in future, discard output with the given tag.
 * no effect if not currently added.
 **/
LIB_API 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.
 **/
LIB_API void debug_filter_clear();

/**
 * indicate if the given text would be printed.
 * useful for a series of debug_printfs - avoids needing to add a tag to
 * each of their format strings.
 **/
LIB_API bool debug_filter_allows(const char* text);

/**
 * call debug_puts if debug_filter_allows allows the string.
 **/
LIB_API void debug_puts_filtered(const char* text);

/**
 * write an error description and all logs into crashlog.txt
 * (in unicode format).
 *
 * @param text description of the error (including stack trace);
 * typically generated by debug_BuildErrorMessage.
 *
 * @return Status; ERR::REENTERED if reentered via recursion or
 * multithreading (not allowed since an infinite loop may result).
 **/
LIB_API Status debug_WriteCrashlog(const char* text);


//-----------------------------------------------------------------------------
// assertions
//-----------------------------------------------------------------------------

/**
 * ensure 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!
 *
 * to pass more information to users at runtime, you can write
 * ENSURE(expression && "descriptive string").
 **/
#define ENSURE(expr)\
    do\
    {\
        static atomic_bool suppress__;\
        if(!(expr))\
        {\
            switch(debug_OnAssertionFailure(WIDEN(#expr), &suppress__, WIDEN(__FILE__), __LINE__, __func__))\
            {\
            case ER_CONTINUE:\
                break;\
            case ER_BREAK:\
            default:\
                debug_break();\
                break;\
            }\
        }\
    }\
    while(0)

/**
 * same as ENSURE in debug mode, does nothing in release mode.
 * (we don't override the `assert' macro because users may
 * inadvertently include <assert.h> afterwards)
 * (we do not provide an MFC-style VERIFY macro because the distinction
 * between ENSURE and VERIFY is unclear. to always run code but only
 * check for success in debug builds without raising unused-variable warnings,
 * use ASSERT + UNUSED2.)
 **/
#define ASSERT(expr) ENSURE(expr)
#ifdef NDEBUG
# undef ASSERT
# define ASSERT(expr)
#endif

/**
 * display the error dialog with the given text. this is less error-prone than
 * ENSURE(0 && "text"). note that "conditional expression is constant" warnings
 * are disabled anyway.
 *
 * if being able to suppress the warning is desirable (e.g. for self-tests),
 * then use DEBUG_WARN_ERR instead.
 **/
#define debug_warn(expr) ENSURE(0 && (expr))

/**
 * display the error dialog with text corresponding to the given error code.
 * used by WARN_RETURN_STATUS_IF_ERR et al., which wrap function calls and automatically
 * raise warnings and return to the caller.
 **/
#define DEBUG_WARN_ERR(status)\
    do\
    {\
        static atomic_bool suppress__;\
        switch(debug_OnError(status, &suppress__, WIDEN(__FILE__), __LINE__, __func__))\
        {\
        case ER_CONTINUE:\
            break;\
        case ER_BREAK:\
        default:\
            debug_break();\
            break;\
        }\
    }\
    while(0)

/**
 * called when a ENSURE/ASSERT fails;
 * notifies the user via debug_DisplayError.
 *
 * @param assert_expr the expression that failed; typically passed as
 * \#expr in the assert macro.
 * @param suppress see debug_DisplayError.
 * @param file, line source file name and line number of the spot that failed
 * @param func name of the function containing it
 * @return ErrorReaction (user's choice: continue running or stop?)
 **/
LIB_API ErrorReaction debug_OnAssertionFailure(const wchar_t* assert_expr, atomic_bool* suppress, const wchar_t* file, int line, const char* func) ANALYZER_NORETURN;

/**
 * called when a DEBUG_WARN_ERR indicates an error occurred;
 * notifies the user via debug_DisplayError.
 *
 * @param err Status value indicating the error that occurred
 * @param suppress see debug_DisplayError.
 * @param file, line source file name and line number of the spot that failed
 * @param func name of the function containing it
 * @return ErrorReaction (user's choice: continue running or stop?)
 **/
LIB_API ErrorReaction debug_OnError(Status err, atomic_bool* suppress, const wchar_t* file, int line, const char* func) ANALYZER_NORETURN;


/**
 * suppress (prevent from showing) the error dialog from subsequent
 * debug_OnError for the given Status.
 *
 * rationale: for edge cases in some functions, warnings are raised in
 * addition to returning an error code. self-tests deliberately trigger
 * these cases and check for the latter but shouldn't cause the former.
 * we therefore need to squelch them.
 *
 * @param err the Status to skip.
 *
 * note: only one concurrent skip request is allowed; call
 * debug_StopSkippingErrors before the next debug_SkipErrors.
 */
LIB_API void debug_SkipErrors(Status err);

/**
 * @return how many errors were skipped since the call to debug_SkipErrors()
 **/
LIB_API size_t debug_StopSkippingErrors();


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

namespace ERR
{
    const Status SYM_NO_STACK_FRAMES_FOUND = -100400;
    const Status SYM_UNRETRIEVABLE_STATIC  = -100401;
    const Status SYM_UNRETRIEVABLE         = -100402;
    const Status SYM_TYPE_INFO_UNAVAILABLE = -100403;
    const Status SYM_INTERNAL_ERROR        = -100404;
    const Status SYM_UNSUPPORTED           = -100405;
    const Status SYM_CHILD_NOT_FOUND       = -100406;
    // this limit is to prevent infinite recursion.
    const Status SYM_NESTING_LIMIT         = -100407;
    // this limit is to prevent large symbols (e.g. arrays or linked lists)
    // from taking up all available output space.
    const Status SYM_SINGLE_SYMBOL_LIMIT   = -100408;
}

namespace INFO
{
    // one of the dump_sym* functions decided not to output anything at
    // all (e.g. for member functions in UDTs - we don't want those).
    // therefore, skip any post-symbol formatting (e.g. ) as well.
    const Status SYM_SUPPRESS_OUTPUT       = +100409;
}


/**
 * Maximum number of characters (including null terminator) written to
 * user's buffers by debug_ResolveSymbol.
 **/
static const size_t DEBUG_SYMBOL_CHARS = 1000;
static const size_t DEBUG_FILE_CHARS = 100;

/**
 * read and return symbol information for the given address.
 *
 * NOTE: the PDB implementation is rather slow (~500 us).
 *
 * @param ptr_of_interest address of symbol (e.g. function, variable)
 * @param sym_name optional out; holds at least DEBUG_SYMBOL_CHARS;
 *   receives symbol name returned via debug info.
 * @param file optional out; holds at least DEBUG_FILE_CHARS;
 *   receives base name only (no path; see rationale in wdbg_sym) of
 *   source file containing the symbol.
 * @param line optional out; receives source file line number of symbol.
 *
 * note: all of the output parameters are optional; we pass back as much
 * information as is available and desired.
 * @return Status; INFO::OK iff any information was successfully
 * retrieved and stored.
 **/
LIB_API Status debug_ResolveSymbol(void* ptr_of_interest, wchar_t* sym_name, wchar_t* file, int* line);

static const size_t DEBUG_CONTEXT_SIZE = 2048;  // Win32 CONTEXT is currently 1232 bytes

/**
 * @param context must point to an instance of the platform-specific type
 *   (e.g. CONTEXT) or CACHE_ALIGNED storage of DEBUG_CONTEXT_SIZE bytes.
 **/
LIB_API Status debug_CaptureContext(void* context);


/**
 * write a complete stack trace (including values of local variables) into
 * the specified buffer.
 *
 * @param buf Target buffer.
 * @param maxChars Max chars of buffer (should be several thousand).
 * @param context Platform-specific representation of execution state
 *        (e.g. Win32 CONTEXT). either specify an SEH exception's
 *        context record or use debug_CaptureContext to retrieve the current state.
 *        Rationale: intermediates such as debug_DisplayError change the
 *        context, so it should be captured as soon as possible.
 * @param lastFuncToSkip Is used for omitting error-reporting functions like
 *        debug_OnAssertionFailure from the stack trace. It is either 0 (skip nothing) or
 *        a substring of a function's name (this allows platform-independent
 *        matching of stdcall-decorated names).
 *        Rationale: this is safer than specifying a fixed number of frames,
 *        which can be incorrect due to inlining.
 * @return Status; ERR::REENTERED if reentered via recursion or
 *         multithreading (not allowed since static data is used).
 **/
LIB_API Status debug_DumpStack(wchar_t* buf, size_t maxChars, void* context, const wchar_t* lastFuncToSkip);


//-----------------------------------------------------------------------------
// 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).
 **/
LIB_API void debug_puts(const char* text);

/**
 * return the caller of a certain function on the call stack.
 *
 * this function is useful for recording (partial) stack traces for
 * memory allocation tracking, etc.
 *
 * @param context, lastFuncToSkip - see debug_DumpStack
 * @return address of the caller
 **/
LIB_API void* debug_GetCaller(void* context, const wchar_t* lastFuncToSkip);

/**
 * check if a pointer appears to be totally invalid.
 *
 * 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.
 *
 * @param p pointer
 * @return 1 if totally bogus, otherwise 0.
 **/
LIB_API int debug_IsPointerBogus(const void* p);

/// does the given pointer appear to point to code?
LIB_API bool debug_IsCodePointer(void* p);

/// does the given pointer appear to point to the stack?
LIB_API bool debug_IsStackPointer(void* p);


/**
 * inform the debugger of the current thread's name.
 *
 * (threads are easier to keep apart when they are identified by
 * name rather than TID.)
 **/
LIB_API void debug_SetThreadName(const char* name);


/**
 * holds memory for an error message.
 **/
struct ErrorMessageMem
{
    // rationale:
    // - error messages with stack traces require a good deal of memory
    //   (hundreds of KB). static buffers of that size are undesirable.
    // - the heap may be corrupted, so don't use malloc.
    //   instead, "lib/sysdep/vm.h" functions should be safe.
    // - alloca is a bit iffy (the stack may be maxed out), non-portable and
    //   complicates the code because it can't be allocated by a subroutine.
    // - this method is probably slow, but error messages aren't built often.
    //   if necessary, first try malloc and use mmap if that fails.
    void* pa_mem;
};

/**
 * free memory from the error message.
 *
 * @param emm ErrorMessageMem*
 **/
LIB_API void debug_FreeErrorMessage(ErrorMessageMem* emm);

/**
 * build a string describing the given error.
 *
 * this is a helper function used by debug_DumpStack and is made available
 * so that the self-test doesn't have to display the error dialog.
 *
 * @param description: general description of the problem.
 * @param fn_only filename (no path) of source file that triggered the error.
 * @param line, func: exact position of the error.
 * @param context, lastFuncToSkip: see debug_DumpStack.
 * @param emm memory for the error message. caller should allocate
 * stack memory and set alloc_buf*; if not, there will be no
 * fallback in case heap alloc fails. should be freed via
 * debug_FreeErrorMessage when no longer needed.
 **/
LIB_API const wchar_t* debug_BuildErrorMessage(const wchar_t* description, const wchar_t* fn_only, int line, const char* func, void* context, const wchar_t* lastFuncToSkip, ErrorMessageMem* emm);

#endif  // #ifndef INCLUDED_DEBUG