tor-browser

pngerror.c (26351B)

---

/* pngerror.c - stub functions for i/o and memory allocation
*
* Copyright (c) 2018-2025 Cosmin Truta
* Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
* Copyright (c) 1996-1997 Andreas Dilger
* Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
*
* This code is released under the libpng license.
* For conditions of distribution and use, see the disclaimer
* and license in png.h
*
* This file provides a location for all error handling.  Users who
* need special error handling are expected to write replacement functions
* and use png_set_error_fn() to use those functions.  See the instructions
* at each function.
*/

#include "pngpriv.h"

#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)

static PNG_FUNCTION(void /* PRIVATE */,
png_default_error,(png_const_structrp png_ptr, png_const_charp error_message),
   PNG_NORETURN);

#ifdef PNG_WARNINGS_SUPPORTED
static void /* PRIVATE */
png_default_warning(png_const_structrp png_ptr,
   png_const_charp warning_message);
#endif /* WARNINGS */

/* This function is called whenever there is a fatal error.  This function
* should not be changed.  If there is a need to handle errors differently,
* you should supply a replacement error function and use png_set_error_fn()
* to replace the error function at run-time.
*/
#ifdef PNG_ERROR_TEXT_SUPPORTED
PNG_FUNCTION(void,PNGAPI
png_error,(png_const_structrp png_ptr, png_const_charp error_message),
   PNG_NORETURN)
{
  if (png_ptr != NULL && png_ptr->error_fn != NULL)
     (*(png_ptr->error_fn))(png_constcast(png_structrp,png_ptr),
         error_message);

  /* If the custom handler doesn't exist, or if it returns,
     use the default handler, which will not return. */
  png_default_error(png_ptr, error_message);
}
#else
PNG_FUNCTION(void,PNGAPI
png_err,(png_const_structrp png_ptr),PNG_NORETURN)
{
  /* Prior to 1.5.2 the error_fn received a NULL pointer, expressed
   * erroneously as '\0', instead of the empty string "".  This was
   * apparently an error, introduced in libpng-1.2.20, and png_default_error
   * will crash in this case.
   */
  if (png_ptr != NULL && png_ptr->error_fn != NULL)
     (*(png_ptr->error_fn))(png_constcast(png_structrp,png_ptr), "");

  /* If the custom handler doesn't exist, or if it returns,
     use the default handler, which will not return. */
  png_default_error(png_ptr, "");
}
#endif /* ERROR_TEXT */

/* Utility to safely appends strings to a buffer.  This never errors out so
* error checking is not required in the caller.
*/
size_t
png_safecat(png_charp buffer, size_t bufsize, size_t pos,
   png_const_charp string)
{
  if (buffer != NULL && pos < bufsize)
  {
     if (string != NULL)
        while (*string != '\0' && pos < bufsize-1)
          buffer[pos++] = *string++;

     buffer[pos] = '\0';
  }

  return pos;
}

#if defined(PNG_WARNINGS_SUPPORTED) || defined(PNG_TIME_RFC1123_SUPPORTED)
/* Utility to dump an unsigned value into a buffer, given a start pointer and
* and end pointer (which should point just *beyond* the end of the buffer!)
* Returns the pointer to the start of the formatted string.
*/
png_charp
png_format_number(png_const_charp start, png_charp end, int format,
   png_alloc_size_t number)
{
  int count = 0;    /* number of digits output */
  int mincount = 1; /* minimum number required */
  int output = 0;   /* digit output (for the fixed point format) */

  *--end = '\0';

  /* This is written so that the loop always runs at least once, even with
   * number zero.
   */
  while (end > start && (number != 0 || count < mincount))
  {

     static const char digits[] = "0123456789ABCDEF";

     switch (format)
     {
        case PNG_NUMBER_FORMAT_fixed:
           /* Needs five digits (the fraction) */
           mincount = 5;
           if (output != 0 || number % 10 != 0)
           {
              *--end = digits[number % 10];
              output = 1;
           }
           number /= 10;
           break;

        case PNG_NUMBER_FORMAT_02u:
           /* Expects at least 2 digits. */
           mincount = 2;
           /* FALLTHROUGH */

        case PNG_NUMBER_FORMAT_u:
           *--end = digits[number % 10];
           number /= 10;
           break;

        case PNG_NUMBER_FORMAT_02x:
           /* This format expects at least two digits */
           mincount = 2;
           /* FALLTHROUGH */

        case PNG_NUMBER_FORMAT_x:
           *--end = digits[number & 0xf];
           number >>= 4;
           break;

        default: /* an error */
           number = 0;
           break;
     }

     /* Keep track of the number of digits added */
     ++count;

     /* Float a fixed number here: */
     if ((format == PNG_NUMBER_FORMAT_fixed) && (count == 5) && (end > start))
     {
        /* End of the fraction, but maybe nothing was output?  In that case
         * drop the decimal point.  If the number is a true zero handle that
         * here.
         */
        if (output != 0)
           *--end = '.';
        else if (number == 0) /* and !output */
           *--end = '0';
     }
  }

  return end;
}
#endif

#ifdef PNG_WARNINGS_SUPPORTED
/* This function is called whenever there is a non-fatal error.  This function
* should not be changed.  If there is a need to handle warnings differently,
* you should supply a replacement warning function and use
* png_set_error_fn() to replace the warning function at run-time.
*/
void PNGAPI
png_warning(png_const_structrp png_ptr, png_const_charp warning_message)
{
  int offset = 0;
  if (png_ptr != NULL && png_ptr->warning_fn != NULL)
     (*(png_ptr->warning_fn))(png_constcast(png_structrp,png_ptr),
         warning_message + offset);
  else
     png_default_warning(png_ptr, warning_message + offset);
}

/* These functions support 'formatted' warning messages with up to
* PNG_WARNING_PARAMETER_COUNT parameters.  In the format string the parameter
* is introduced by @<number>, where 'number' starts at 1.  This follows the
* standard established by X/Open for internationalizable error messages.
*/
void
png_warning_parameter(png_warning_parameters p, int number,
   png_const_charp string)
{
  if (number > 0 && number <= PNG_WARNING_PARAMETER_COUNT)
     (void)png_safecat(p[number-1], (sizeof p[number-1]), 0, string);
}

void
png_warning_parameter_unsigned(png_warning_parameters p, int number, int format,
   png_alloc_size_t value)
{
  char buffer[PNG_NUMBER_BUFFER_SIZE] = {0};
  png_warning_parameter(p, number, PNG_FORMAT_NUMBER(buffer, format, value));
}

void
png_warning_parameter_signed(png_warning_parameters p, int number, int format,
   png_int_32 value)
{
  png_alloc_size_t u;
  png_charp str;
  char buffer[PNG_NUMBER_BUFFER_SIZE] = {0};

  /* Avoid overflow by doing the negate in a png_alloc_size_t: */
  u = (png_alloc_size_t)value;
  if (value < 0)
     u = ~u + 1;

  str = PNG_FORMAT_NUMBER(buffer, format, u);

  if (value < 0 && str > buffer)
     *--str = '-';

  png_warning_parameter(p, number, str);
}

void
png_formatted_warning(png_const_structrp png_ptr, png_warning_parameters p,
   png_const_charp message)
{
  /* The internal buffer is just 192 bytes - enough for all our messages,
   * overflow doesn't happen because this code checks!  If someone figures
   * out how to send us a message longer than 192 bytes, all that will
   * happen is that the message will be truncated appropriately.
   */
  size_t i = 0; /* Index in the msg[] buffer: */
  char msg[192];

  /* Each iteration through the following loop writes at most one character
   * to msg[i++] then returns here to validate that there is still space for
   * the trailing '\0'.  It may (in the case of a parameter) read more than
   * one character from message[]; it must check for '\0' and continue to the
   * test if it finds the end of string.
   */
  while (i<(sizeof msg)-1 && *message != '\0')
  {
     /* '@' at end of string is now just printed (previously it was skipped);
      * it is an error in the calling code to terminate the string with @.
      */
     if (p != NULL && *message == '@' && message[1] != '\0')
     {
        int parameter_char = *++message; /* Consume the '@' */
        static const char valid_parameters[] = "123456789";
        int parameter = 0;

        /* Search for the parameter digit, the index in the string is the
         * parameter to use.
         */
        while (valid_parameters[parameter] != parameter_char &&
           valid_parameters[parameter] != '\0')
           ++parameter;

        /* If the parameter digit is out of range it will just get printed. */
        if (parameter < PNG_WARNING_PARAMETER_COUNT)
        {
           /* Append this parameter */
           png_const_charp parm = p[parameter];
           png_const_charp pend = p[parameter] + (sizeof p[parameter]);

           /* No need to copy the trailing '\0' here, but there is no guarantee
            * that parm[] has been initialized, so there is no guarantee of a
            * trailing '\0':
            */
           while (i<(sizeof msg)-1 && *parm != '\0' && parm < pend)
              msg[i++] = *parm++;

           /* Consume the parameter digit too: */
           ++message;
           continue;
        }

        /* else not a parameter and there is a character after the @ sign; just
         * copy that.  This is known not to be '\0' because of the test above.
         */
     }

     /* At this point *message can't be '\0', even in the bad parameter case
      * above where there is a lone '@' at the end of the message string.
      */
     msg[i++] = *message++;
  }

  /* i is always less than (sizeof msg), so: */
  msg[i] = '\0';

  /* And this is the formatted message. It may be larger than
   * PNG_MAX_ERROR_TEXT, but that is only used for 'chunk' errors and these
   * are not (currently) formatted.
   */
  png_warning(png_ptr, msg);
}
#endif /* WARNINGS */

#ifdef PNG_BENIGN_ERRORS_SUPPORTED
void PNGAPI
png_benign_error(png_const_structrp png_ptr, png_const_charp error_message)
{
  if ((png_ptr->flags & PNG_FLAG_BENIGN_ERRORS_WARN) != 0)
  {
#     ifdef PNG_READ_SUPPORTED
        if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
           png_ptr->chunk_name != 0)
           png_chunk_warning(png_ptr, error_message);
        else
#     endif
     png_warning(png_ptr, error_message);
  }

  else
  {
#     ifdef PNG_READ_SUPPORTED
        if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
           png_ptr->chunk_name != 0)
           png_chunk_error(png_ptr, error_message);
        else
#     endif
     png_error(png_ptr, error_message);
  }

#  ifndef PNG_ERROR_TEXT_SUPPORTED
     PNG_UNUSED(error_message)
#  endif
}

void /* PRIVATE */
png_app_warning(png_const_structrp png_ptr, png_const_charp error_message)
{
  if ((png_ptr->flags & PNG_FLAG_APP_WARNINGS_WARN) != 0)
     png_warning(png_ptr, error_message);
  else
     png_error(png_ptr, error_message);

#  ifndef PNG_ERROR_TEXT_SUPPORTED
     PNG_UNUSED(error_message)
#  endif
}

void /* PRIVATE */
png_app_error(png_const_structrp png_ptr, png_const_charp error_message)
{
  if ((png_ptr->flags & PNG_FLAG_APP_ERRORS_WARN) != 0)
     png_warning(png_ptr, error_message);
  else
     png_error(png_ptr, error_message);

#  ifndef PNG_ERROR_TEXT_SUPPORTED
     PNG_UNUSED(error_message)
#  endif
}
#endif /* BENIGN_ERRORS */

#define PNG_MAX_ERROR_TEXT 196 /* Currently limited by profile_error in png.c */
#if defined(PNG_WARNINGS_SUPPORTED) || \
  (defined(PNG_READ_SUPPORTED) && defined(PNG_ERROR_TEXT_SUPPORTED))
/* These utilities are used internally to build an error message that relates
* to the current chunk.  The chunk name comes from png_ptr->chunk_name,
* which is used to prefix the message.  The message is limited in length
* to 63 bytes. The name characters are output as hex digits wrapped in []
* if the character is invalid.
*/
#define isnonalpha(c) ((c) < 65 || (c) > 122 || ((c) > 90 && (c) < 97))
static const char png_digit[16] = {
  '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
  'A', 'B', 'C', 'D', 'E', 'F'
};

static void /* PRIVATE */
png_format_buffer(png_const_structrp png_ptr, png_charp buffer, png_const_charp
   error_message)
{
  png_uint_32 chunk_name = png_ptr->chunk_name;
  int iout = 0, ishift = 24;

  while (ishift >= 0)
  {
     int c = (int)(chunk_name >> ishift) & 0xff;

     ishift -= 8;
     if (isnonalpha(c) != 0)
     {
        buffer[iout++] = PNG_LITERAL_LEFT_SQUARE_BRACKET;
        buffer[iout++] = png_digit[(c & 0xf0) >> 4];
        buffer[iout++] = png_digit[c & 0x0f];
        buffer[iout++] = PNG_LITERAL_RIGHT_SQUARE_BRACKET;
     }

     else
     {
        buffer[iout++] = (char)c;
     }
  }

  if (error_message == NULL)
     buffer[iout] = '\0';

  else
  {
     int iin = 0;

     buffer[iout++] = ':';
     buffer[iout++] = ' ';

     while (iin < PNG_MAX_ERROR_TEXT-1 && error_message[iin] != '\0')
        buffer[iout++] = error_message[iin++];

     /* iin < PNG_MAX_ERROR_TEXT, so the following is safe: */
     buffer[iout] = '\0';
  }
}
#endif /* WARNINGS || ERROR_TEXT */

#if defined(PNG_READ_SUPPORTED) && defined(PNG_ERROR_TEXT_SUPPORTED)
PNG_FUNCTION(void,PNGAPI
png_chunk_error,(png_const_structrp png_ptr, png_const_charp error_message),
   PNG_NORETURN)
{
  char msg[18+PNG_MAX_ERROR_TEXT];
  if (png_ptr == NULL)
     png_error(png_ptr, error_message);

  else
  {
     png_format_buffer(png_ptr, msg, error_message);
     png_error(png_ptr, msg);
  }
}
#endif /* READ && ERROR_TEXT */

#ifdef PNG_WARNINGS_SUPPORTED
void PNGAPI
png_chunk_warning(png_const_structrp png_ptr, png_const_charp warning_message)
{
  char msg[18+PNG_MAX_ERROR_TEXT];
  if (png_ptr == NULL)
     png_warning(png_ptr, warning_message);

  else
  {
     png_format_buffer(png_ptr, msg, warning_message);
     png_warning(png_ptr, msg);
  }
}
#endif /* WARNINGS */

#ifdef PNG_READ_SUPPORTED
#ifdef PNG_BENIGN_ERRORS_SUPPORTED
void PNGAPI
png_chunk_benign_error(png_const_structrp png_ptr, png_const_charp
   error_message)
{
  if ((png_ptr->flags & PNG_FLAG_BENIGN_ERRORS_WARN) != 0)
     png_chunk_warning(png_ptr, error_message);

  else
     png_chunk_error(png_ptr, error_message);

#  ifndef PNG_ERROR_TEXT_SUPPORTED
     PNG_UNUSED(error_message)
#  endif
}
#endif
#endif /* READ */

void /* PRIVATE */
png_chunk_report(png_const_structrp png_ptr, png_const_charp message, int error)
{
#  ifndef PNG_WARNINGS_SUPPORTED
     PNG_UNUSED(message)
#  endif

  /* This is always supported, but for just read or just write it
   * unconditionally does the right thing.
   */
#  if defined(PNG_READ_SUPPORTED) && defined(PNG_WRITE_SUPPORTED)
     if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0)
#  endif

#  ifdef PNG_READ_SUPPORTED
     {
        if (error < PNG_CHUNK_ERROR)
           png_chunk_warning(png_ptr, message);

        else
           png_chunk_benign_error(png_ptr, message);
     }
#  endif

#  if defined(PNG_READ_SUPPORTED) && defined(PNG_WRITE_SUPPORTED)
     else if ((png_ptr->mode & PNG_IS_READ_STRUCT) == 0)
#  endif

#  ifdef PNG_WRITE_SUPPORTED
     {
        if (error < PNG_CHUNK_WRITE_ERROR)
           png_app_warning(png_ptr, message);

        else
           png_app_error(png_ptr, message);
     }
#  endif
}

#ifdef PNG_ERROR_TEXT_SUPPORTED
#ifdef PNG_FLOATING_POINT_SUPPORTED
PNG_FUNCTION(void,
png_fixed_error,(png_const_structrp png_ptr, png_const_charp name),PNG_NORETURN)
{
#  define fixed_message "fixed point overflow in "
#  define fixed_message_ln ((sizeof fixed_message)-1)
  unsigned int  iin;
  char msg[fixed_message_ln+PNG_MAX_ERROR_TEXT];
  memcpy(msg, fixed_message, fixed_message_ln);
  iin = 0;
  if (name != NULL)
     while (iin < (PNG_MAX_ERROR_TEXT-1) && name[iin] != 0)
     {
        msg[fixed_message_ln + iin] = name[iin];
        ++iin;
     }
  msg[fixed_message_ln + iin] = 0;
  png_error(png_ptr, msg);
}
#endif
#endif

#ifdef PNG_SETJMP_SUPPORTED
/* This API only exists if ANSI-C style error handling is used,
* otherwise it is necessary for png_default_error to be overridden.
*/
jmp_buf* PNGAPI
png_set_longjmp_fn(png_structrp png_ptr, png_longjmp_ptr longjmp_fn,
   size_t jmp_buf_size)
{
  /* From libpng 1.6.0 the app gets one chance to set a 'jmpbuf_size' value
   * and it must not change after that.  Libpng doesn't care how big the
   * buffer is, just that it doesn't change.
   *
   * If the buffer size is no *larger* than the size of jmp_buf when libpng is
   * compiled a built in jmp_buf is returned; this preserves the pre-1.6.0
   * semantics that this call will not fail.  If the size is larger, however,
   * the buffer is allocated and this may fail, causing the function to return
   * NULL.
   */
  if (png_ptr == NULL)
     return NULL;

  if (png_ptr->jmp_buf_ptr == NULL)
  {
     png_ptr->jmp_buf_size = 0; /* not allocated */

     if (jmp_buf_size <= (sizeof png_ptr->jmp_buf_local))
        png_ptr->jmp_buf_ptr = &png_ptr->jmp_buf_local;

     else
     {
        png_ptr->jmp_buf_ptr = png_voidcast(jmp_buf *,
            png_malloc_warn(png_ptr, jmp_buf_size));

        if (png_ptr->jmp_buf_ptr == NULL)
           return NULL; /* new NULL return on OOM */

        png_ptr->jmp_buf_size = jmp_buf_size;
     }
  }

  else /* Already allocated: check the size */
  {
     size_t size = png_ptr->jmp_buf_size;

     if (size == 0)
     {
        size = (sizeof png_ptr->jmp_buf_local);
        if (png_ptr->jmp_buf_ptr != &png_ptr->jmp_buf_local)
        {
           /* This is an internal error in libpng: somehow we have been left
            * with a stack allocated jmp_buf when the application regained
            * control.  It's always possible to fix this up, but for the moment
            * this is a png_error because that makes it easy to detect.
            */
           png_error(png_ptr, "Libpng jmp_buf still allocated");
           /* png_ptr->jmp_buf_ptr = &png_ptr->jmp_buf_local; */
        }
     }

     if (size != jmp_buf_size)
     {
        png_warning(png_ptr, "Application jmp_buf size changed");
        return NULL; /* caller will probably crash: no choice here */
     }
  }

  /* Finally fill in the function, now we have a satisfactory buffer. It is
   * valid to change the function on every call.
   */
  png_ptr->longjmp_fn = longjmp_fn;
  return png_ptr->jmp_buf_ptr;
}

void /* PRIVATE */
png_free_jmpbuf(png_structrp png_ptr)
{
  if (png_ptr != NULL)
  {
     jmp_buf *jb = png_ptr->jmp_buf_ptr;

     /* A size of 0 is used to indicate a local, stack, allocation of the
      * pointer; used here and in png.c
      */
     if (jb != NULL && png_ptr->jmp_buf_size > 0)
     {

        /* This stuff is so that a failure to free the error control structure
         * does not leave libpng in a state with no valid error handling: the
         * free always succeeds, if there is an error it gets ignored.
         */
        if (jb != &png_ptr->jmp_buf_local)
        {
           /* Make an internal, libpng, jmp_buf to return here */
           jmp_buf free_jmp_buf;

           if (!setjmp(free_jmp_buf))
           {
              png_ptr->jmp_buf_ptr = &free_jmp_buf; /* come back here */
              png_ptr->jmp_buf_size = 0; /* stack allocation */
              png_ptr->longjmp_fn = longjmp;
              png_free(png_ptr, jb); /* Return to setjmp on error */
           }
        }
     }

     /* *Always* cancel everything out: */
     png_ptr->jmp_buf_size = 0;
     png_ptr->jmp_buf_ptr = NULL;
     png_ptr->longjmp_fn = 0;
  }
}
#endif

/* This is the default error handling function.  Note that replacements for
* this function MUST NOT RETURN, or the program will likely crash.  This
* function is used by default, or if the program supplies NULL for the
* error function pointer in png_set_error_fn().
*/
static PNG_FUNCTION(void /* PRIVATE */,
png_default_error,(png_const_structrp png_ptr, png_const_charp error_message),
   PNG_NORETURN)
{
#ifdef PNG_CONSOLE_IO_SUPPORTED
  fprintf(stderr, "libpng error: %s", error_message ? error_message :
     "undefined");
  fprintf(stderr, PNG_STRING_NEWLINE);
#else
  PNG_UNUSED(error_message) /* Make compiler happy */
#endif
  png_longjmp(png_ptr, 1);
}

PNG_FUNCTION(void,PNGAPI
png_longjmp,(png_const_structrp png_ptr, int val),PNG_NORETURN)
{
#ifdef PNG_SETJMP_SUPPORTED
  if (png_ptr != NULL && png_ptr->longjmp_fn != NULL &&
      png_ptr->jmp_buf_ptr != NULL)
     png_ptr->longjmp_fn(*png_ptr->jmp_buf_ptr, val);
#else
  PNG_UNUSED(png_ptr)
  PNG_UNUSED(val)
#endif

  /* If control reaches this point, png_longjmp() must not return. The only
   * choice is to terminate the whole process (or maybe the thread); to do
   * this the ANSI-C abort() function is used unless a different method is
   * implemented by overriding the default configuration setting for
   * PNG_ABORT().
   */
  PNG_ABORT();
}

#ifdef PNG_WARNINGS_SUPPORTED
/* This function is called when there is a warning, but the library thinks
* it can continue anyway.  Replacement functions don't have to do anything
* here if you don't want them to.  In the default configuration, png_ptr is
* not used, but it is passed in case it may be useful.
*/
static void /* PRIVATE */
png_default_warning(png_const_structrp png_ptr, png_const_charp warning_message)
{
#ifdef PNG_CONSOLE_IO_SUPPORTED
  fprintf(stderr, "libpng warning: %s", warning_message);
  fprintf(stderr, PNG_STRING_NEWLINE);
#else
  PNG_UNUSED(warning_message) /* Make compiler happy */
#endif
  PNG_UNUSED(png_ptr) /* Make compiler happy */
}
#endif /* WARNINGS */

/* This function is called when the application wants to use another method
* of handling errors and warnings.  Note that the error function MUST NOT
* return to the calling routine or serious problems will occur.  The return
* method used in the default routine calls longjmp(png_ptr->jmp_buf_ptr, 1)
*/
void PNGAPI
png_set_error_fn(png_structrp png_ptr, png_voidp error_ptr,
   png_error_ptr error_fn, png_error_ptr warning_fn)
{
  if (png_ptr == NULL)
     return;

  png_ptr->error_ptr = error_ptr;
  png_ptr->error_fn = error_fn;
#ifdef PNG_WARNINGS_SUPPORTED
  png_ptr->warning_fn = warning_fn;
#else
  PNG_UNUSED(warning_fn)
#endif
}


/* This function returns a pointer to the error_ptr associated with the user
* functions.  The application should free any memory associated with this
* pointer before png_write_destroy and png_read_destroy are called.
*/
png_voidp PNGAPI
png_get_error_ptr(png_const_structrp png_ptr)
{
  if (png_ptr == NULL)
     return NULL;

  return (png_voidp)png_ptr->error_ptr;
}


#ifdef PNG_ERROR_NUMBERS_SUPPORTED
void PNGAPI
png_set_strip_error_numbers(png_structrp png_ptr, png_uint_32 strip_mode)
{
  PNG_UNUSED(png_ptr)
  PNG_UNUSED(strip_mode)
}
#endif

#if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
  defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
  /* Currently the above both depend on SETJMP_SUPPORTED, however it would be
   * possible to implement without setjmp support just so long as there is some
   * way to handle the error return here:
   */
PNG_FUNCTION(void /* PRIVATE */, (PNGCBAPI
png_safe_error),(png_structp png_nonconst_ptr, png_const_charp error_message),
   PNG_NORETURN)
{
  png_const_structrp png_ptr = png_nonconst_ptr;
  png_imagep image = png_voidcast(png_imagep, png_ptr->error_ptr);

  /* An error is always logged here, overwriting anything (typically a warning)
   * that is already there:
   */
  if (image != NULL)
  {
     png_safecat(image->message, (sizeof image->message), 0, error_message);
     image->warning_or_error |= PNG_IMAGE_ERROR;

     /* Retrieve the jmp_buf from within the png_control, making this work for
      * C++ compilation too is pretty tricky: C++ wants a pointer to the first
      * element of a jmp_buf, but C doesn't tell us the type of that.
      */
     if (image->opaque != NULL && image->opaque->error_buf != NULL)
        longjmp(png_control_jmp_buf(image->opaque), 1);

     /* Missing longjmp buffer, the following is to help debugging: */
     {
        size_t pos = png_safecat(image->message, (sizeof image->message), 0,
            "bad longjmp: ");
        png_safecat(image->message, (sizeof image->message), pos,
            error_message);
     }
  }

  /* Here on an internal programming error. */
  abort();
}

#ifdef PNG_WARNINGS_SUPPORTED
void /* PRIVATE */ PNGCBAPI
png_safe_warning(png_structp png_nonconst_ptr, png_const_charp warning_message)
{
  png_const_structrp png_ptr = png_nonconst_ptr;
  png_imagep image = png_voidcast(png_imagep, png_ptr->error_ptr);

  /* A warning is only logged if there is no prior warning or error. */
  if (image->warning_or_error == 0)
  {
     png_safecat(image->message, (sizeof image->message), 0, warning_message);
     image->warning_or_error |= PNG_IMAGE_WARNING;
  }
}
#endif

int /* PRIVATE */
png_safe_execute(png_imagep image, int (*function)(png_voidp), png_voidp arg)
{
  const png_voidp saved_error_buf = image->opaque->error_buf;
  jmp_buf safe_jmpbuf;

  /* Safely execute function(arg), with png_error returning back here. */
  if (setjmp(safe_jmpbuf) == 0)
  {
     int result;

     image->opaque->error_buf = safe_jmpbuf;
     result = function(arg);
     image->opaque->error_buf = saved_error_buf;

     if (result)
        return 1; /* success */
  }

  /* The function failed either because of a caught png_error and a regular
   * return of false above or because of an uncaught png_error from the
   * function itself.  Ensure that the error_buf is always set back to the
   * value saved above:
   */
  image->opaque->error_buf = saved_error_buf;

  /* On the final false return, when about to return control to the caller, the
   * image is freed (png_image_free does this check but it is duplicated here
   * for clarity:
   */
  if (saved_error_buf == NULL)
     png_image_free(image);

  return 0; /* failure */
}
#endif /* SIMPLIFIED READ || SIMPLIFIED_WRITE */
#endif /* READ || WRITE */