media/libpng/pngerror.c

   1
   2 /* pngerror.c - stub functions for i/o and memory allocation
   3  *
   4  * Copyright (c) 2018 Cosmin Truta
   5  * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
   6  * Copyright (c) 1996-1997 Andreas Dilger
   7  * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
   8  *
   9  * This code is released under the libpng license.
  10  * For conditions of distribution and use, see the disclaimer
  11  * and license in png.h
  12  *
  13  * This file provides a location for all error handling.  Users who
  14  * need special error handling are expected to write replacement functions
  15  * and use png_set_error_fn() to use those functions.  See the instructions
  16  * at each function.
  17  */
  18
  19 #include "pngpriv.h"
  20
  21 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
  22
  23 static PNG_FUNCTION(void, png_default_error,PNGARG((png_const_structrp png_ptr,
  24     png_const_charp error_message)),PNG_NORETURN);
  25
  26 #ifdef PNG_WARNINGS_SUPPORTED
  27 static void /* PRIVATE */
  28 png_default_warning PNGARG((png_const_structrp png_ptr,
  29     png_const_charp warning_message));
  30 #endif /* WARNINGS */
  31
  32 /* This function is called whenever there is a fatal error.  This function
  33  * should not be changed.  If there is a need to handle errors differently,
  34  * you should supply a replacement error function and use png_set_error_fn()
  35  * to replace the error function at run-time.
  36  */
  37 #ifdef PNG_ERROR_TEXT_SUPPORTED
  38 PNG_FUNCTION(void,PNGAPI
  39 png_error,(png_const_structrp png_ptr, png_const_charp error_message),
  40     PNG_NORETURN)
  41 {
  42 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
  43    char msg[16];
  44    if (png_ptr != NULL)
  45    {
  46       if ((png_ptr->flags &
  47          (PNG_FLAG_STRIP_ERROR_NUMBERS|PNG_FLAG_STRIP_ERROR_TEXT)) != 0)
  48       {
  49          if (*error_message == PNG_LITERAL_SHARP)
  50          {
  51             /* Strip "#nnnn " from beginning of error message. */
  52             int offset;
  53             for (offset = 1; offset<15; offset++)
  54                if (error_message[offset] == ' ')
  55                   break;
  56
  57             if ((png_ptr->flags & PNG_FLAG_STRIP_ERROR_TEXT) != 0)
  58             {
  59                int i;
  60                for (i = 0; i < offset - 1; i++)
  61                   msg[i] = error_message[i + 1];
  62                msg[i - 1] = '\0';
  63                error_message = msg;
  64             }
  65
  66             else
  67                error_message += offset;
  68          }
  69
  70          else
  71          {
  72             if ((png_ptr->flags & PNG_FLAG_STRIP_ERROR_TEXT) != 0)
  73             {
  74                msg[0] = '0';
  75                msg[1] = '\0';
  76                error_message = msg;
  77             }
  78          }
  79       }
  80    }
  81 #endif
  82    if (png_ptr != NULL && png_ptr->error_fn != NULL)
  83       (*(png_ptr->error_fn))(png_constcast(png_structrp,png_ptr),
  84           error_message);
  85
  86    /* If the custom handler doesn't exist, or if it returns,
  87       use the default handler, which will not return. */
  88    png_default_error(png_ptr, error_message);
  89 }
  90 #else
  91 PNG_FUNCTION(void,PNGAPI
  92 png_err,(png_const_structrp png_ptr),PNG_NORETURN)
  93 {
  94    /* Prior to 1.5.2 the error_fn received a NULL pointer, expressed
  95     * erroneously as '\0', instead of the empty string "".  This was
  96     * apparently an error, introduced in libpng-1.2.20, and png_default_error
  97     * will crash in this case.
  98     */
  99    if (png_ptr != NULL && png_ptr->error_fn != NULL)
 100       (*(png_ptr->error_fn))(png_constcast(png_structrp,png_ptr), "");
 101
 102    /* If the custom handler doesn't exist, or if it returns,
 103       use the default handler, which will not return. */
 104    png_default_error(png_ptr, "");
 105 }
 106 #endif /* ERROR_TEXT */
 107
 108 /* Utility to safely appends strings to a buffer.  This never errors out so
 109  * error checking is not required in the caller.
 110  */
 111 size_t
 112 png_safecat(png_charp buffer, size_t bufsize, size_t pos,
 113     png_const_charp string)
 114 {
 115    if (buffer != NULL && pos < bufsize)
 116    {
 117       if (string != NULL)
 118          while (*string != '\0' && pos < bufsize-1)
 119            buffer[pos++] = *string++;
 120
 121       buffer[pos] = '\0';
 122    }
 123
 124    return pos;
 125 }
 126
 127 #if defined(PNG_WARNINGS_SUPPORTED) || defined(PNG_TIME_RFC1123_SUPPORTED)
 128 /* Utility to dump an unsigned value into a buffer, given a start pointer and
 129  * and end pointer (which should point just *beyond* the end of the buffer!)
 130  * Returns the pointer to the start of the formatted string.
 131  */
 132 png_charp
 133 png_format_number(png_const_charp start, png_charp end, int format,
 134     png_alloc_size_t number)
 135 {
 136    int count = 0;    /* number of digits output */
 137    int mincount = 1; /* minimum number required */
 138    int output = 0;   /* digit output (for the fixed point format) */
 139
 140    *--end = '\0';
 141
 142    /* This is written so that the loop always runs at least once, even with
 143     * number zero.
 144     */
 145    while (end > start && (number != 0 || count < mincount))
 146    {
 147
 148       static const char digits[] = "0123456789ABCDEF";
 149
 150       switch (format)
 151       {
 152          case PNG_NUMBER_FORMAT_fixed:
 153             /* Needs five digits (the fraction) */
 154             mincount = 5;
 155             if (output != 0 || number % 10 != 0)
 156             {
 157                *--end = digits[number % 10];
 158                output = 1;
 159             }
 160             number /= 10;
 161             break;
 162
 163          case PNG_NUMBER_FORMAT_02u:
 164             /* Expects at least 2 digits. */
 165             mincount = 2;
 166             /* FALLTHROUGH */
 167
 168          case PNG_NUMBER_FORMAT_u:
 169             *--end = digits[number % 10];
 170             number /= 10;
 171             break;
 172
 173          case PNG_NUMBER_FORMAT_02x:
 174             /* This format expects at least two digits */
 175             mincount = 2;
 176             /* FALLTHROUGH */
 177
 178          case PNG_NUMBER_FORMAT_x:
 179             *--end = digits[number & 0xf];
 180             number >>= 4;
 181             break;
 182
 183          default: /* an error */
 184             number = 0;
 185             break;
 186       }
 187
 188       /* Keep track of the number of digits added */
 189       ++count;
 190
 191       /* Float a fixed number here: */
 192       if ((format == PNG_NUMBER_FORMAT_fixed) && (count == 5) && (end > start))
 193       {
 194          /* End of the fraction, but maybe nothing was output?  In that case
 195           * drop the decimal point.  If the number is a true zero handle that
 196           * here.
 197           */
 198          if (output != 0)
 199             *--end = '.';
 200          else if (number == 0) /* and !output */
 201             *--end = '0';
 202       }
 203    }
 204
 205    return end;
 206 }
 207 #endif
 208
 209 #ifdef PNG_WARNINGS_SUPPORTED
 210 /* This function is called whenever there is a non-fatal error.  This function
 211  * should not be changed.  If there is a need to handle warnings differently,
 212  * you should supply a replacement warning function and use
 213  * png_set_error_fn() to replace the warning function at run-time.
 214  */
 215 void PNGAPI
 216 png_warning(png_const_structrp png_ptr, png_const_charp warning_message)
 217 {
 218    int offset = 0;
 219    if (png_ptr != NULL)
 220    {
 221 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
 222    if ((png_ptr->flags &
 223        (PNG_FLAG_STRIP_ERROR_NUMBERS|PNG_FLAG_STRIP_ERROR_TEXT)) != 0)
 224 #endif
 225       {
 226          if (*warning_message == PNG_LITERAL_SHARP)
 227          {
 228             for (offset = 1; offset < 15; offset++)
 229                if (warning_message[offset] == ' ')
 230                   break;
 231          }
 232       }
 233    }
 234    if (png_ptr != NULL && png_ptr->warning_fn != NULL)
 235       (*(png_ptr->warning_fn))(png_constcast(png_structrp,png_ptr),
 236           warning_message + offset);
 237    else
 238       png_default_warning(png_ptr, warning_message + offset);
 239 }
 240
 241 /* These functions support 'formatted' warning messages with up to
 242  * PNG_WARNING_PARAMETER_COUNT parameters.  In the format string the parameter
 243  * is introduced by @<number>, where 'number' starts at 1.  This follows the
 244  * standard established by X/Open for internationalizable error messages.
 245  */
 246 void
 247 png_warning_parameter(png_warning_parameters p, int number,
 248     png_const_charp string)
 249 {
 250    if (number > 0 && number <= PNG_WARNING_PARAMETER_COUNT)
 251       (void)png_safecat(p[number-1], (sizeof p[number-1]), 0, string);
 252 }
 253
 254 void
 255 png_warning_parameter_unsigned(png_warning_parameters p, int number, int format,
 256     png_alloc_size_t value)
 257 {
 258    char buffer[PNG_NUMBER_BUFFER_SIZE];
 259    png_warning_parameter(p, number, PNG_FORMAT_NUMBER(buffer, format, value));
 260 }
 261
 262 void
 263 png_warning_parameter_signed(png_warning_parameters p, int number, int format,
 264     png_int_32 value)
 265 {
 266    png_alloc_size_t u;
 267    png_charp str;
 268    char buffer[PNG_NUMBER_BUFFER_SIZE];
 269
 270    /* Avoid overflow by doing the negate in a png_alloc_size_t: */
 271    u = (png_alloc_size_t)value;
 272    if (value < 0)
 273       u = ~u + 1;
 274
 275    str = PNG_FORMAT_NUMBER(buffer, format, u);
 276
 277    if (value < 0 && str > buffer)
 278       *--str = '-';
 279
 280    png_warning_parameter(p, number, str);
 281 }
 282
 283 void
 284 png_formatted_warning(png_const_structrp png_ptr, png_warning_parameters p,
 285     png_const_charp message)
 286 {
 287    /* The internal buffer is just 192 bytes - enough for all our messages,
 288     * overflow doesn't happen because this code checks!  If someone figures
 289     * out how to send us a message longer than 192 bytes, all that will
 290     * happen is that the message will be truncated appropriately.
 291     */
 292    size_t i = 0; /* Index in the msg[] buffer: */
 293    char msg[192];
 294
 295    /* Each iteration through the following loop writes at most one character
 296     * to msg[i++] then returns here to validate that there is still space for
 297     * the trailing '\0'.  It may (in the case of a parameter) read more than
 298     * one character from message[]; it must check for '\0' and continue to the
 299     * test if it finds the end of string.
 300     */
 301    while (i<(sizeof msg)-1 && *message != '\0')
 302    {
 303       /* '@' at end of string is now just printed (previously it was skipped);
 304        * it is an error in the calling code to terminate the string with @.
 305        */
 306       if (p != NULL && *message == '@' && message[1] != '\0')
 307       {
 308          int parameter_char = *++message; /* Consume the '@' */
 309          static const char valid_parameters[] = "123456789";
 310          int parameter = 0;
 311
 312          /* Search for the parameter digit, the index in the string is the
 313           * parameter to use.
 314           */
 315          while (valid_parameters[parameter] != parameter_char &&
 316             valid_parameters[parameter] != '\0')
 317             ++parameter;
 318
 319          /* If the parameter digit is out of range it will just get printed. */
 320          if (parameter < PNG_WARNING_PARAMETER_COUNT)
 321          {
 322             /* Append this parameter */
 323             png_const_charp parm = p[parameter];
 324             png_const_charp pend = p[parameter] + (sizeof p[parameter]);
 325
 326             /* No need to copy the trailing '\0' here, but there is no guarantee
 327              * that parm[] has been initialized, so there is no guarantee of a
 328              * trailing '\0':
 329              */
 330             while (i<(sizeof msg)-1 && *parm != '\0' && parm < pend)
 331                msg[i++] = *parm++;
 332
 333             /* Consume the parameter digit too: */
 334             ++message;
 335             continue;
 336          }
 337
 338          /* else not a parameter and there is a character after the @ sign; just
 339           * copy that.  This is known not to be '\0' because of the test above.
 340           */
 341       }
 342
 343       /* At this point *message can't be '\0', even in the bad parameter case
 344        * above where there is a lone '@' at the end of the message string.
 345        */
 346       msg[i++] = *message++;
 347    }
 348
 349    /* i is always less than (sizeof msg), so: */
 350    msg[i] = '\0';
 351
 352    /* And this is the formatted message. It may be larger than
 353     * PNG_MAX_ERROR_TEXT, but that is only used for 'chunk' errors and these
 354     * are not (currently) formatted.
 355     */
 356    png_warning(png_ptr, msg);
 357 }
 358 #endif /* WARNINGS */
 359
 360 #ifdef PNG_BENIGN_ERRORS_SUPPORTED
 361 void PNGAPI
 362 png_benign_error(png_const_structrp png_ptr, png_const_charp error_message)
 363 {
 364    if ((png_ptr->flags & PNG_FLAG_BENIGN_ERRORS_WARN) != 0)
 365    {
 366 #     ifdef PNG_READ_SUPPORTED
 367          if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
 368             png_ptr->chunk_name != 0)
 369             png_chunk_warning(png_ptr, error_message);
 370          else
 371 #     endif
 372       png_warning(png_ptr, error_message);
 373    }
 374
 375    else
 376    {
 377 #     ifdef PNG_READ_SUPPORTED
 378          if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
 379             png_ptr->chunk_name != 0)
 380             png_chunk_error(png_ptr, error_message);
 381          else
 382 #     endif
 383       png_error(png_ptr, error_message);
 384    }
 385
 386 #  ifndef PNG_ERROR_TEXT_SUPPORTED
 387       PNG_UNUSED(error_message)
 388 #  endif
 389 }
 390
 391 void /* PRIVATE */
 392 png_app_warning(png_const_structrp png_ptr, png_const_charp error_message)
 393 {
 394    if ((png_ptr->flags & PNG_FLAG_APP_WARNINGS_WARN) != 0)
 395       png_warning(png_ptr, error_message);
 396    else
 397       png_error(png_ptr, error_message);
 398
 399 #  ifndef PNG_ERROR_TEXT_SUPPORTED
 400       PNG_UNUSED(error_message)
 401 #  endif
 402 }
 403
 404 void /* PRIVATE */
 405 png_app_error(png_const_structrp png_ptr, png_const_charp error_message)
 406 {
 407    if ((png_ptr->flags & PNG_FLAG_APP_ERRORS_WARN) != 0)
 408       png_warning(png_ptr, error_message);
 409    else
 410       png_error(png_ptr, error_message);
 411
 412 #  ifndef PNG_ERROR_TEXT_SUPPORTED
 413       PNG_UNUSED(error_message)
 414 #  endif
 415 }
 416 #endif /* BENIGN_ERRORS */
 417
 418 #define PNG_MAX_ERROR_TEXT 196 /* Currently limited by profile_error in png.c */
 419 #if defined(PNG_WARNINGS_SUPPORTED) || \
 420    (defined(PNG_READ_SUPPORTED) && defined(PNG_ERROR_TEXT_SUPPORTED))
 421 /* These utilities are used internally to build an error message that relates
 422  * to the current chunk.  The chunk name comes from png_ptr->chunk_name,
 423  * which is used to prefix the message.  The message is limited in length
 424  * to 63 bytes. The name characters are output as hex digits wrapped in []
 425  * if the character is invalid.
 426  */
 427 #define isnonalpha(c) ((c) < 65 || (c) > 122 || ((c) > 90 && (c) < 97))
 428 static const char png_digit[16] = {
 429    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 430    'A', 'B', 'C', 'D', 'E', 'F'
 431 };
 432
 433 static void /* PRIVATE */
 434 png_format_buffer(png_const_structrp png_ptr, png_charp buffer, png_const_charp
 435     error_message)
 436 {
 437    png_uint_32 chunk_name = png_ptr->chunk_name;
 438    int iout = 0, ishift = 24;
 439
 440    while (ishift >= 0)
 441    {
 442       int c = (int)(chunk_name >> ishift) & 0xff;
 443
 444       ishift -= 8;
 445       if (isnonalpha(c) != 0)
 446       {
 447          buffer[iout++] = PNG_LITERAL_LEFT_SQUARE_BRACKET;
 448          buffer[iout++] = png_digit[(c & 0xf0) >> 4];
 449          buffer[iout++] = png_digit[c & 0x0f];
 450          buffer[iout++] = PNG_LITERAL_RIGHT_SQUARE_BRACKET;
 451       }
 452
 453       else
 454       {
 455          buffer[iout++] = (char)c;
 456       }
 457    }
 458
 459    if (error_message == NULL)
 460       buffer[iout] = '\0';
 461
 462    else
 463    {
 464       int iin = 0;
 465
 466       buffer[iout++] = ':';
 467       buffer[iout++] = ' ';
 468
 469       while (iin < PNG_MAX_ERROR_TEXT-1 && error_message[iin] != '\0')
 470          buffer[iout++] = error_message[iin++];
 471
 472       /* iin < PNG_MAX_ERROR_TEXT, so the following is safe: */
 473       buffer[iout] = '\0';
 474    }
 475 }
 476 #endif /* WARNINGS || ERROR_TEXT */
 477
 478 #if defined(PNG_READ_SUPPORTED) && defined(PNG_ERROR_TEXT_SUPPORTED)
 479 PNG_FUNCTION(void,PNGAPI
 480 png_chunk_error,(png_const_structrp png_ptr, png_const_charp error_message),
 481     PNG_NORETURN)
 482 {
 483    char msg[18+PNG_MAX_ERROR_TEXT];
 484    if (png_ptr == NULL)
 485       png_error(png_ptr, error_message);
 486
 487    else
 488    {
 489       png_format_buffer(png_ptr, msg, error_message);
 490       png_error(png_ptr, msg);
 491    }
 492 }
 493 #endif /* READ && ERROR_TEXT */
 494
 495 #ifdef PNG_WARNINGS_SUPPORTED
 496 void PNGAPI
 497 png_chunk_warning(png_const_structrp png_ptr, png_const_charp warning_message)
 498 {
 499    char msg[18+PNG_MAX_ERROR_TEXT];
 500    if (png_ptr == NULL)
 501       png_warning(png_ptr, warning_message);
 502
 503    else
 504    {
 505       png_format_buffer(png_ptr, msg, warning_message);
 506       png_warning(png_ptr, msg);
 507    }
 508 }
 509 #endif /* WARNINGS */
 510
 511 #ifdef PNG_READ_SUPPORTED
 512 #ifdef PNG_BENIGN_ERRORS_SUPPORTED
 513 void PNGAPI
 514 png_chunk_benign_error(png_const_structrp png_ptr, png_const_charp
 515     error_message)
 516 {
 517    if ((png_ptr->flags & PNG_FLAG_BENIGN_ERRORS_WARN) != 0)
 518       png_chunk_warning(png_ptr, error_message);
 519
 520    else
 521       png_chunk_error(png_ptr, error_message);
 522
 523 #  ifndef PNG_ERROR_TEXT_SUPPORTED
 524       PNG_UNUSED(error_message)
 525 #  endif
 526 }
 527 #endif
 528 #endif /* READ */
 529
 530 void /* PRIVATE */
 531 png_chunk_report(png_const_structrp png_ptr, png_const_charp message, int error)
 532 {
 533 #  ifndef PNG_WARNINGS_SUPPORTED
 534       PNG_UNUSED(message)
 535 #  endif
 536
 537    /* This is always supported, but for just read or just write it
 538     * unconditionally does the right thing.
 539     */
 540 #  if defined(PNG_READ_SUPPORTED) && defined(PNG_WRITE_SUPPORTED)
 541       if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0)
 542 #  endif
 543
 544 #  ifdef PNG_READ_SUPPORTED
 545       {
 546          if (error < PNG_CHUNK_ERROR)
 547             png_chunk_warning(png_ptr, message);
 548
 549          else
 550             png_chunk_benign_error(png_ptr, message);
 551       }
 552 #  endif
 553
 554 #  if defined(PNG_READ_SUPPORTED) && defined(PNG_WRITE_SUPPORTED)
 555       else if ((png_ptr->mode & PNG_IS_READ_STRUCT) == 0)
 556 #  endif
 557
 558 #  ifdef PNG_WRITE_SUPPORTED
 559       {
 560          if (error < PNG_CHUNK_WRITE_ERROR)
 561             png_app_warning(png_ptr, message);
 562
 563          else
 564             png_app_error(png_ptr, message);
 565       }
 566 #  endif
 567 }
 568
 569 #ifdef PNG_ERROR_TEXT_SUPPORTED
 570 #ifdef PNG_FLOATING_POINT_SUPPORTED
 571 PNG_FUNCTION(void,
 572 png_fixed_error,(png_const_structrp png_ptr, png_const_charp name),PNG_NORETURN)
 573 {
 574 #  define fixed_message "fixed point overflow in "
 575 #  define fixed_message_ln ((sizeof fixed_message)-1)
 576    unsigned int  iin;
 577    char msg[fixed_message_ln+PNG_MAX_ERROR_TEXT];
 578    memcpy(msg, fixed_message, fixed_message_ln);
 579    iin = 0;
 580    if (name != NULL)
 581       while (iin < (PNG_MAX_ERROR_TEXT-1) && name[iin] != 0)
 582       {
 583          msg[fixed_message_ln + iin] = name[iin];
 584          ++iin;
 585       }
 586    msg[fixed_message_ln + iin] = 0;
 587    png_error(png_ptr, msg);
 588 }
 589 #endif
 590 #endif
 591
 592 #ifdef PNG_SETJMP_SUPPORTED
 593 /* This API only exists if ANSI-C style error handling is used,
 594  * otherwise it is necessary for png_default_error to be overridden.
 595  */
 596 jmp_buf* PNGAPI
 597 png_set_longjmp_fn(png_structrp png_ptr, png_longjmp_ptr longjmp_fn,
 598     size_t jmp_buf_size)
 599 {
 600    /* From libpng 1.6.0 the app gets one chance to set a 'jmpbuf_size' value
 601     * and it must not change after that.  Libpng doesn't care how big the
 602     * buffer is, just that it doesn't change.
 603     *
 604     * If the buffer size is no *larger* than the size of jmp_buf when libpng is
 605     * compiled a built in jmp_buf is returned; this preserves the pre-1.6.0
 606     * semantics that this call will not fail.  If the size is larger, however,
 607     * the buffer is allocated and this may fail, causing the function to return
 608     * NULL.
 609     */
 610    if (png_ptr == NULL)
 611       return NULL;
 612
 613    if (png_ptr->jmp_buf_ptr == NULL)
 614    {
 615       png_ptr->jmp_buf_size = 0; /* not allocated */
 616
 617       if (jmp_buf_size <= (sizeof png_ptr->jmp_buf_local))
 618          png_ptr->jmp_buf_ptr = &png_ptr->jmp_buf_local;
 619
 620       else
 621       {
 622          png_ptr->jmp_buf_ptr = png_voidcast(jmp_buf *,
 623              png_malloc_warn(png_ptr, jmp_buf_size));
 624
 625          if (png_ptr->jmp_buf_ptr == NULL)
 626             return NULL; /* new NULL return on OOM */
 627
 628          png_ptr->jmp_buf_size = jmp_buf_size;
 629       }
 630    }
 631
 632    else /* Already allocated: check the size */
 633    {
 634       size_t size = png_ptr->jmp_buf_size;
 635
 636       if (size == 0)
 637       {
 638          size = (sizeof png_ptr->jmp_buf_local);
 639          if (png_ptr->jmp_buf_ptr != &png_ptr->jmp_buf_local)
 640          {
 641             /* This is an internal error in libpng: somehow we have been left
 642              * with a stack allocated jmp_buf when the application regained
 643              * control.  It's always possible to fix this up, but for the moment
 644              * this is a png_error because that makes it easy to detect.
 645              */
 646             png_error(png_ptr, "Libpng jmp_buf still allocated");
 647             /* png_ptr->jmp_buf_ptr = &png_ptr->jmp_buf_local; */
 648          }
 649       }
 650
 651       if (size != jmp_buf_size)
 652       {
 653          png_warning(png_ptr, "Application jmp_buf size changed");
 654          return NULL; /* caller will probably crash: no choice here */
 655       }
 656    }
 657
 658    /* Finally fill in the function, now we have a satisfactory buffer. It is
 659     * valid to change the function on every call.
 660     */
 661    png_ptr->longjmp_fn = longjmp_fn;
 662    return png_ptr->jmp_buf_ptr;
 663 }
 664
 665 void /* PRIVATE */
 666 png_free_jmpbuf(png_structrp png_ptr)
 667 {
 668    if (png_ptr != NULL)
 669    {
 670       jmp_buf *jb = png_ptr->jmp_buf_ptr;
 671
 672       /* A size of 0 is used to indicate a local, stack, allocation of the
 673        * pointer; used here and in png.c
 674        */
 675       if (jb != NULL && png_ptr->jmp_buf_size > 0)
 676       {
 677
 678          /* This stuff is so that a failure to free the error control structure
 679           * does not leave libpng in a state with no valid error handling: the
 680           * free always succeeds, if there is an error it gets ignored.
 681           */
 682          if (jb != &png_ptr->jmp_buf_local)
 683          {
 684             /* Make an internal, libpng, jmp_buf to return here */
 685             jmp_buf free_jmp_buf;
 686
 687             if (!setjmp(free_jmp_buf))
 688             {
 689                png_ptr->jmp_buf_ptr = &free_jmp_buf; /* come back here */
 690                png_ptr->jmp_buf_size = 0; /* stack allocation */
 691                png_ptr->longjmp_fn = longjmp;
 692                png_free(png_ptr, jb); /* Return to setjmp on error */
 693             }
 694          }
 695       }
 696
 697       /* *Always* cancel everything out: */
 698       png_ptr->jmp_buf_size = 0;
 699       png_ptr->jmp_buf_ptr = NULL;
 700       png_ptr->longjmp_fn = 0;
 701    }
 702 }
 703 #endif
 704
 705 /* This is the default error handling function.  Note that replacements for
 706  * this function MUST NOT RETURN, or the program will likely crash.  This
 707  * function is used by default, or if the program supplies NULL for the
 708  * error function pointer in png_set_error_fn().
 709  */
 710 static PNG_FUNCTION(void /* PRIVATE */,
 711 png_default_error,(png_const_structrp png_ptr, png_const_charp error_message),
 712     PNG_NORETURN)
 713 {
 714 #ifdef PNG_CONSOLE_IO_SUPPORTED
 715 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
 716    /* Check on NULL only added in 1.5.4 */
 717    if (error_message != NULL && *error_message == PNG_LITERAL_SHARP)
 718    {
 719       /* Strip "#nnnn " from beginning of error message. */
 720       int offset;
 721       char error_number[16];
 722       for (offset = 0; offset<15; offset++)
 723       {
 724          error_number[offset] = error_message[offset + 1];
 725          if (error_message[offset] == ' ')
 726             break;
 727       }
 728
 729       if ((offset > 1) && (offset < 15))
 730       {
 731          error_number[offset - 1] = '\0';
 732          fprintf(stderr, "libpng error no. %s: %s",
 733              error_number, error_message + offset + 1);
 734          fprintf(stderr, PNG_STRING_NEWLINE);
 735       }
 736
 737       else
 738       {
 739          fprintf(stderr, "libpng error: %s, offset=%d",
 740              error_message, offset);
 741          fprintf(stderr, PNG_STRING_NEWLINE);
 742       }
 743    }
 744    else
 745 #endif
 746    {
 747       fprintf(stderr, "libpng error: %s", error_message ? error_message :
 748          "undefined");
 749       fprintf(stderr, PNG_STRING_NEWLINE);
 750    }
 751 #else
 752    PNG_UNUSED(error_message) /* Make compiler happy */
 753 #endif
 754    png_longjmp(png_ptr, 1);
 755 }
 756
 757 PNG_FUNCTION(void,PNGAPI
 758 png_longjmp,(png_const_structrp png_ptr, int val),PNG_NORETURN)
 759 {
 760 #ifdef PNG_SETJMP_SUPPORTED
 761    if (png_ptr != NULL && png_ptr->longjmp_fn != NULL &&
 762        png_ptr->jmp_buf_ptr != NULL)
 763       png_ptr->longjmp_fn(*png_ptr->jmp_buf_ptr, val);
 764 #else
 765    PNG_UNUSED(png_ptr)
 766    PNG_UNUSED(val)
 767 #endif
 768
 769    /* If control reaches this point, png_longjmp() must not return. The only
 770     * choice is to terminate the whole process (or maybe the thread); to do
 771     * this the ANSI-C abort() function is used unless a different method is
 772     * implemented by overriding the default configuration setting for
 773     * PNG_ABORT().
 774     */
 775    PNG_ABORT();
 776 }
 777
 778 #ifdef PNG_WARNINGS_SUPPORTED
 779 /* This function is called when there is a warning, but the library thinks
 780  * it can continue anyway.  Replacement functions don't have to do anything
 781  * here if you don't want them to.  In the default configuration, png_ptr is
 782  * not used, but it is passed in case it may be useful.
 783  */
 784 static void /* PRIVATE */
 785 png_default_warning(png_const_structrp png_ptr, png_const_charp warning_message)
 786 {
 787 #ifdef PNG_CONSOLE_IO_SUPPORTED
 788 #  ifdef PNG_ERROR_NUMBERS_SUPPORTED
 789    if (*warning_message == PNG_LITERAL_SHARP)
 790    {
 791       int offset;
 792       char warning_number[16];
 793       for (offset = 0; offset < 15; offset++)
 794       {
 795          warning_number[offset] = warning_message[offset + 1];
 796          if (warning_message[offset] == ' ')
 797             break;
 798       }
 799
 800       if ((offset > 1) && (offset < 15))
 801       {
 802          warning_number[offset + 1] = '\0';
 803          fprintf(stderr, "libpng warning no. %s: %s",
 804              warning_number, warning_message + offset);
 805          fprintf(stderr, PNG_STRING_NEWLINE);
 806       }
 807
 808       else
 809       {
 810          fprintf(stderr, "libpng warning: %s",
 811              warning_message);
 812          fprintf(stderr, PNG_STRING_NEWLINE);
 813       }
 814    }
 815    else
 816 #  endif
 817
 818    {
 819       fprintf(stderr, "libpng warning: %s", warning_message);
 820       fprintf(stderr, PNG_STRING_NEWLINE);
 821    }
 822 #else
 823    PNG_UNUSED(warning_message) /* Make compiler happy */
 824 #endif
 825    PNG_UNUSED(png_ptr) /* Make compiler happy */
 826 }
 827 #endif /* WARNINGS */
 828
 829 /* This function is called when the application wants to use another method
 830  * of handling errors and warnings.  Note that the error function MUST NOT
 831  * return to the calling routine or serious problems will occur.  The return
 832  * method used in the default routine calls longjmp(png_ptr->jmp_buf_ptr, 1)
 833  */
 834 void PNGAPI
 835 png_set_error_fn(png_structrp png_ptr, png_voidp error_ptr,
 836     png_error_ptr error_fn, png_error_ptr warning_fn)
 837 {
 838    if (png_ptr == NULL)
 839       return;
 840
 841    png_ptr->error_ptr = error_ptr;
 842    png_ptr->error_fn = error_fn;
 843 #ifdef PNG_WARNINGS_SUPPORTED
 844    png_ptr->warning_fn = warning_fn;
 845 #else
 846    PNG_UNUSED(warning_fn)
 847 #endif
 848 }
 849
 850
 851 /* This function returns a pointer to the error_ptr associated with the user
 852  * functions.  The application should free any memory associated with this
 853  * pointer before png_write_destroy and png_read_destroy are called.
 854  */
 855 png_voidp PNGAPI
 856 png_get_error_ptr(png_const_structrp png_ptr)
 857 {
 858    if (png_ptr == NULL)
 859       return NULL;
 860
 861    return ((png_voidp)png_ptr->error_ptr);
 862 }
 863
 864
 865 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
 866 void PNGAPI
 867 png_set_strip_error_numbers(png_structrp png_ptr, png_uint_32 strip_mode)
 868 {
 869    if (png_ptr != NULL)
 870    {
 871       png_ptr->flags &=
 872          ((~(PNG_FLAG_STRIP_ERROR_NUMBERS |
 873          PNG_FLAG_STRIP_ERROR_TEXT))&strip_mode);
 874    }
 875 }
 876 #endif
 877
 878 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
 879    defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
 880    /* Currently the above both depend on SETJMP_SUPPORTED, however it would be
 881     * possible to implement without setjmp support just so long as there is some
 882     * way to handle the error return here:
 883     */
 884 PNG_FUNCTION(void /* PRIVATE */, (PNGCBAPI
 885 png_safe_error),(png_structp png_nonconst_ptr, png_const_charp error_message),
 886     PNG_NORETURN)
 887 {
 888    png_const_structrp png_ptr = png_nonconst_ptr;
 889    png_imagep image = png_voidcast(png_imagep, png_ptr->error_ptr);
 890
 891    /* An error is always logged here, overwriting anything (typically a warning)
 892     * that is already there:
 893     */
 894    if (image != NULL)
 895    {
 896       png_safecat(image->message, (sizeof image->message), 0, error_message);
 897       image->warning_or_error |= PNG_IMAGE_ERROR;
 898
 899       /* Retrieve the jmp_buf from within the png_control, making this work for
 900        * C++ compilation too is pretty tricky: C++ wants a pointer to the first
 901        * element of a jmp_buf, but C doesn't tell us the type of that.
 902        */
 903       if (image->opaque != NULL && image->opaque->error_buf != NULL)
 904          longjmp(png_control_jmp_buf(image->opaque), 1);
 905
 906       /* Missing longjmp buffer, the following is to help debugging: */
 907       {
 908          size_t pos = png_safecat(image->message, (sizeof image->message), 0,
 909              "bad longjmp: ");
 910          png_safecat(image->message, (sizeof image->message), pos,
 911              error_message);
 912       }
 913    }
 914
 915    /* Here on an internal programming error. */
 916    abort();
 917 }
 918
 919 #ifdef PNG_WARNINGS_SUPPORTED
 920 void /* PRIVATE */ PNGCBAPI
 921 png_safe_warning(png_structp png_nonconst_ptr, png_const_charp warning_message)
 922 {
 923    png_const_structrp png_ptr = png_nonconst_ptr;
 924    png_imagep image = png_voidcast(png_imagep, png_ptr->error_ptr);
 925
 926    /* A warning is only logged if there is no prior warning or error. */
 927    if (image->warning_or_error == 0)
 928    {
 929       png_safecat(image->message, (sizeof image->message), 0, warning_message);
 930       image->warning_or_error |= PNG_IMAGE_WARNING;
 931    }
 932 }
 933 #endif
 934
 935 int /* PRIVATE */
 936 png_safe_execute(png_imagep image_in, int (*function)(png_voidp), png_voidp arg)
 937 {
 938    volatile png_imagep image = image_in;
 939    volatile int result;
 940    volatile png_voidp saved_error_buf;
 941    jmp_buf safe_jmpbuf;
 942
 943    /* Safely execute function(arg) with png_error returning to this function. */
 944    saved_error_buf = image->opaque->error_buf;
 945    result = setjmp(safe_jmpbuf) == 0;
 946
 947    if (result != 0)
 948    {
 949
 950       image->opaque->error_buf = safe_jmpbuf;
 951       result = function(arg);
 952    }
 953
 954    image->opaque->error_buf = saved_error_buf;
 955
 956    /* And do the cleanup prior to any failure return. */
 957    if (result == 0)
 958       png_image_free(image);
 959
 960    return result;
 961 }
 962 #endif /* SIMPLIFIED READ || SIMPLIFIED_WRITE */
 963 #endif /* READ || WRITE */