src/png/pngerror.c

   1
   2 /* pngerror.c - stub functions for i/o and memory allocation
   3  *
   4  * Last changed in libpng 1.5.7 [December 15, 2011]
   5  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
   6  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
   7  * (Version 0.88 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_structp 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_structp png_ptr,
  29    png_const_charp warning_message));
  30 #endif /* PNG_WARNINGS_SUPPORTED */
  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_structp png_ptr, png_const_charp error_message),PNG_NORETURN)
  40 {
  41 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
  42    char msg[16];
  43    if (png_ptr != NULL)
  44    {
  45       if (png_ptr->flags&
  46          (PNG_FLAG_STRIP_ERROR_NUMBERS|PNG_FLAG_STRIP_ERROR_TEXT))
  47       {
  48          if (*error_message == PNG_LITERAL_SHARP)
  49          {
  50             /* Strip "#nnnn " from beginning of error message. */
  51             int offset;
  52             for (offset = 1; offset<15; offset++)
  53                if (error_message[offset] == ' ')
  54                   break;
  55
  56             if (png_ptr->flags&PNG_FLAG_STRIP_ERROR_TEXT)
  57             {
  58                int i;
  59                for (i = 0; i < offset - 1; i++)
  60                   msg[i] = error_message[i + 1];
  61                msg[i - 1] = '\0';
  62                error_message = msg;
  63             }
  64
  65             else
  66                error_message += offset;
  67       }
  68
  69       else
  70       {
  71          if (png_ptr->flags&PNG_FLAG_STRIP_ERROR_TEXT)
  72          {
  73             msg[0] = '0';
  74             msg[1] = '\0';
  75             error_message = msg;
  76          }
  77        }
  78      }
  79    }
  80 #endif
  81    if (png_ptr != NULL && png_ptr->error_fn != NULL)
  82       (*(png_ptr->error_fn))(png_ptr, error_message);
  83
  84    /* If the custom handler doesn't exist, or if it returns,
  85       use the default handler, which will not return. */
  86    png_default_error(png_ptr, error_message);
  87 }
  88 #else
  89 PNG_FUNCTION(void,PNGAPI
  90 png_err,(png_structp png_ptr),PNG_NORETURN)
  91 {
  92    /* Prior to 1.5.2 the error_fn received a NULL pointer, expressed
  93     * erroneously as '\0', instead of the empty string "".  This was
  94     * apparently an error, introduced in libpng-1.2.20, and png_default_error
  95     * will crash in this case.
  96     */
  97    if (png_ptr != NULL && png_ptr->error_fn != NULL)
  98       (*(png_ptr->error_fn))(png_ptr, "");
  99
 100    /* If the custom handler doesn't exist, or if it returns,
 101       use the default handler, which will not return. */
 102    png_default_error(png_ptr, "");
 103 }
 104 #endif /* PNG_ERROR_TEXT_SUPPORTED */
 105
 106 /* Utility to safely appends strings to a buffer.  This never errors out so
 107  * error checking is not required in the caller.
 108  */
 109 size_t
 110 png_safecat(png_charp buffer, size_t bufsize, size_t pos,
 111    png_const_charp string)
 112 {
 113    if (buffer != NULL && pos < bufsize)
 114    {
 115       if (string != NULL)
 116          while (*string != '\0' && pos < bufsize-1)
 117            buffer[pos++] = *string++;
 118
 119       buffer[pos] = '\0';
 120    }
 121
 122    return pos;
 123 }
 124
 125 #if defined(PNG_WARNINGS_SUPPORTED) || defined(PNG_TIME_RFC1123_SUPPORTED)
 126 /* Utility to dump an unsigned value into a buffer, given a start pointer and
 127  * and end pointer (which should point just *beyond* the end of the buffer!)
 128  * Returns the pointer to the start of the formatted string.
 129  */
 130 png_charp
 131 png_format_number(png_const_charp start, png_charp end, int format,
 132    png_alloc_size_t number)
 133 {
 134    int count = 0;    /* number of digits output */
 135    int mincount = 1; /* minimum number required */
 136    int output = 0;   /* digit output (for the fixed point format) */
 137
 138    *--end = '\0';
 139
 140    /* This is written so that the loop always runs at least once, even with
 141     * number zero.
 142     */
 143    while (end > start && (number != 0 || count < mincount))
 144    {
 145
 146       static const char digits[] = "0123456789ABCDEF";
 147
 148       switch (format)
 149       {
 150          case PNG_NUMBER_FORMAT_fixed:
 151             /* Needs five digits (the fraction) */
 152             mincount = 5;
 153             if (output || number % 10 != 0)
 154             {
 155                *--end = digits[number % 10];
 156                output = 1;
 157             }
 158             number /= 10;
 159             break;
 160
 161          case PNG_NUMBER_FORMAT_02u:
 162             /* Expects at least 2 digits. */
 163             mincount = 2;
 164             /* fall through */
 165
 166          case PNG_NUMBER_FORMAT_u:
 167             *--end = digits[number % 10];
 168             number /= 10;
 169             break;
 170
 171          case PNG_NUMBER_FORMAT_02x:
 172             /* This format expects at least two digits */
 173             mincount = 2;
 174             /* fall through */
 175
 176          case PNG_NUMBER_FORMAT_x:
 177             *--end = digits[number & 0xf];
 178             number >>= 4;
 179             break;
 180
 181          default: /* an error */
 182             number = 0;
 183             break;
 184       }
 185
 186       /* Keep track of the number of digits added */
 187       ++count;
 188
 189       /* Float a fixed number here: */
 190       if (format == PNG_NUMBER_FORMAT_fixed) if (count == 5) if (end > start)
 191       {
 192          /* End of the fraction, but maybe nothing was output?  In that case
 193           * drop the decimal point.  If the number is a true zero handle that
 194           * here.
 195           */
 196          if (output)
 197             *--end = '.';
 198          else if (number == 0) /* and !output */
 199             *--end = '0';
 200       }
 201    }
 202
 203    return end;
 204 }
 205 #endif
 206
 207 #ifdef PNG_WARNINGS_SUPPORTED
 208 /* This function is called whenever there is a non-fatal error.  This function
 209  * should not be changed.  If there is a need to handle warnings differently,
 210  * you should supply a replacement warning function and use
 211  * png_set_error_fn() to replace the warning function at run-time.
 212  */
 213 void PNGAPI
 214 png_warning(png_structp png_ptr, png_const_charp warning_message)
 215 {
 216    int offset = 0;
 217    if (png_ptr != NULL)
 218    {
 219 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
 220    if (png_ptr->flags&
 221        (PNG_FLAG_STRIP_ERROR_NUMBERS|PNG_FLAG_STRIP_ERROR_TEXT))
 222 #endif
 223       {
 224          if (*warning_message == PNG_LITERAL_SHARP)
 225          {
 226             for (offset = 1; offset < 15; offset++)
 227                if (warning_message[offset] == ' ')
 228                   break;
 229          }
 230       }
 231    }
 232    if (png_ptr != NULL && png_ptr->warning_fn != NULL)
 233       (*(png_ptr->warning_fn))(png_ptr, warning_message + offset);
 234    else
 235       png_default_warning(png_ptr, warning_message + offset);
 236 }
 237
 238 /* These functions support 'formatted' warning messages with up to
 239  * PNG_WARNING_PARAMETER_COUNT parameters.  In the format string the parameter
 240  * is introduced by @<number>, where 'number' starts at 1.  This follows the
 241  * standard established by X/Open for internationalizable error messages.
 242  */
 243 void
 244 png_warning_parameter(png_warning_parameters p, int number,
 245    png_const_charp string)
 246 {
 247    if (number > 0 && number <= PNG_WARNING_PARAMETER_COUNT)
 248       (void)png_safecat(p[number-1], (sizeof p[number-1]), 0, string);
 249 }
 250
 251 void
 252 png_warning_parameter_unsigned(png_warning_parameters p, int number, int format,
 253    png_alloc_size_t value)
 254 {
 255    char buffer[PNG_NUMBER_BUFFER_SIZE];
 256    png_warning_parameter(p, number, PNG_FORMAT_NUMBER(buffer, format, value));
 257 }
 258
 259 void
 260 png_warning_parameter_signed(png_warning_parameters p, int number, int format,
 261    png_int_32 value)
 262 {
 263    png_alloc_size_t u;
 264    png_charp str;
 265    char buffer[PNG_NUMBER_BUFFER_SIZE];
 266
 267    /* Avoid overflow by doing the negate in a png_alloc_size_t: */
 268    u = (png_alloc_size_t)value;
 269    if (value < 0)
 270       u = ~u + 1;
 271
 272    str = PNG_FORMAT_NUMBER(buffer, format, u);
 273
 274    if (value < 0 && str > buffer)
 275       *--str = '-';
 276
 277    png_warning_parameter(p, number, str);
 278 }
 279
 280 void
 281 png_formatted_warning(png_structp png_ptr, png_warning_parameters p,
 282    png_const_charp message)
 283 {
 284    /* The internal buffer is just 128 bytes - enough for all our messages,
 285     * overflow doesn't happen because this code checks!
 286     */
 287    size_t i;
 288    char msg[128];
 289
 290    for (i=0; i<(sizeof msg)-1 && *message != '\0'; ++i)
 291    {
 292       if (*message == '@')
 293       {
 294          int parameter = -1;
 295          switch (*++message)
 296          {
 297             case '1':
 298                parameter = 0;
 299                break;
 300
 301             case '2':
 302                parameter = 1;
 303                break;
 304
 305             case '\0':
 306                continue; /* To break out of the for loop above. */
 307
 308             default:
 309                break;
 310          }
 311
 312          if (parameter >= 0 && parameter < PNG_WARNING_PARAMETER_COUNT)
 313          {
 314             /* Append this parameter */
 315             png_const_charp parm = p[parameter];
 316             png_const_charp pend = p[parameter] + (sizeof p[parameter]);
 317
 318             /* No need to copy the trailing '\0' here, but there is no guarantee
 319              * that parm[] has been initialized, so there is no guarantee of a
 320              * trailing '\0':
 321              */
 322             for (; i<(sizeof msg)-1 && parm != '\0' && parm < pend; ++i)
 323                msg[i] = *parm++;
 324
 325             ++message;
 326             continue;
 327          }
 328
 329          /* else not a parameter and there is a character after the @ sign; just
 330           * copy that.
 331           */
 332       }
 333
 334       /* At this point *message can't be '\0', even in the bad parameter case
 335        * above where there is a lone '@' at the end of the message string.
 336        */
 337       msg[i] = *message++;
 338    }
 339
 340    /* i is always less than (sizeof msg), so: */
 341    msg[i] = '\0';
 342
 343    /* And this is the formatted message: */
 344    png_warning(png_ptr, msg);
 345 }
 346 #endif /* PNG_WARNINGS_SUPPORTED */
 347
 348 #ifdef PNG_BENIGN_ERRORS_SUPPORTED
 349 void PNGAPI
 350 png_benign_error(png_structp png_ptr, png_const_charp error_message)
 351 {
 352   if (png_ptr->flags & PNG_FLAG_BENIGN_ERRORS_WARN)
 353      png_warning(png_ptr, error_message);
 354   else
 355      png_error(png_ptr, error_message);
 356 }
 357 #endif
 358
 359 /* These utilities are used internally to build an error message that relates
 360  * to the current chunk.  The chunk name comes from png_ptr->chunk_name,
 361  * this is used to prefix the message.  The message is limited in length
 362  * to 63 bytes, the name characters are output as hex digits wrapped in []
 363  * if the character is invalid.
 364  */
 365 #define isnonalpha(c) ((c) < 65 || (c) > 122 || ((c) > 90 && (c) < 97))
 366 static PNG_CONST char png_digit[16] = {
 367    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 368    'A', 'B', 'C', 'D', 'E', 'F'
 369 };
 370
 371 #define PNG_MAX_ERROR_TEXT 64
 372 #if defined(PNG_WARNINGS_SUPPORTED) || defined(PNG_ERROR_TEXT_SUPPORTED)
 373 static void /* PRIVATE */
 374 png_format_buffer(png_structp png_ptr, png_charp buffer, png_const_charp
 375     error_message)
 376 {
 377    png_uint_32 chunk_name = png_ptr->chunk_name;
 378    int iout = 0, ishift = 24;
 379
 380    while (ishift >= 0)
 381    {
 382       int c = (int)(chunk_name >> ishift) & 0xff;
 383
 384       ishift -= 8;
 385       if (isnonalpha(c))
 386       {
 387          buffer[iout++] = PNG_LITERAL_LEFT_SQUARE_BRACKET;
 388          buffer[iout++] = png_digit[(c & 0xf0) >> 4];
 389          buffer[iout++] = png_digit[c & 0x0f];
 390          buffer[iout++] = PNG_LITERAL_RIGHT_SQUARE_BRACKET;
 391       }
 392
 393       else
 394       {
 395          buffer[iout++] = (char)c;
 396       }
 397    }
 398
 399    if (error_message == NULL)
 400       buffer[iout] = '\0';
 401
 402    else
 403    {
 404       int iin = 0;
 405
 406       buffer[iout++] = ':';
 407       buffer[iout++] = ' ';
 408
 409       while (iin < PNG_MAX_ERROR_TEXT-1 && error_message[iin] != '\0')
 410          buffer[iout++] = error_message[iin++];
 411
 412       /* iin < PNG_MAX_ERROR_TEXT, so the following is safe: */
 413       buffer[iout] = '\0';
 414    }
 415 }
 416 #endif /* PNG_WARNINGS_SUPPORTED || PNG_ERROR_TEXT_SUPPORTED */
 417
 418 #if defined(PNG_READ_SUPPORTED) && defined(PNG_ERROR_TEXT_SUPPORTED)
 419 PNG_FUNCTION(void,PNGAPI
 420 png_chunk_error,(png_structp png_ptr, png_const_charp error_message),
 421    PNG_NORETURN)
 422 {
 423    char msg[18+PNG_MAX_ERROR_TEXT];
 424    if (png_ptr == NULL)
 425       png_error(png_ptr, error_message);
 426
 427    else
 428    {
 429       png_format_buffer(png_ptr, msg, error_message);
 430       png_error(png_ptr, msg);
 431    }
 432 }
 433 #endif /* PNG_READ_SUPPORTED && PNG_ERROR_TEXT_SUPPORTED */
 434
 435 #ifdef PNG_WARNINGS_SUPPORTED
 436 void PNGAPI
 437 png_chunk_warning(png_structp png_ptr, png_const_charp warning_message)
 438 {
 439    char msg[18+PNG_MAX_ERROR_TEXT];
 440    if (png_ptr == NULL)
 441       png_warning(png_ptr, warning_message);
 442
 443    else
 444    {
 445       png_format_buffer(png_ptr, msg, warning_message);
 446       png_warning(png_ptr, msg);
 447    }
 448 }
 449 #endif /* PNG_WARNINGS_SUPPORTED */
 450
 451 #ifdef PNG_READ_SUPPORTED
 452 #ifdef PNG_BENIGN_ERRORS_SUPPORTED
 453 void PNGAPI
 454 png_chunk_benign_error(png_structp png_ptr, png_const_charp error_message)
 455 {
 456    if (png_ptr->flags & PNG_FLAG_BENIGN_ERRORS_WARN)
 457       png_chunk_warning(png_ptr, error_message);
 458
 459    else
 460       png_chunk_error(png_ptr, error_message);
 461 }
 462 #endif
 463 #endif /* PNG_READ_SUPPORTED */
 464
 465 #ifdef PNG_ERROR_TEXT_SUPPORTED
 466 #ifdef PNG_FLOATING_POINT_SUPPORTED
 467 PNG_FUNCTION(void,
 468 png_fixed_error,(png_structp png_ptr, png_const_charp name),PNG_NORETURN)
 469 {
 470 #  define fixed_message "fixed point overflow in "
 471 #  define fixed_message_ln ((sizeof fixed_message)-1)
 472    int  iin;
 473    char msg[fixed_message_ln+PNG_MAX_ERROR_TEXT];
 474    png_memcpy(msg, fixed_message, fixed_message_ln);
 475    iin = 0;
 476    if (name != NULL) while (iin < (PNG_MAX_ERROR_TEXT-1) && name[iin] != 0)
 477    {
 478       msg[fixed_message_ln + iin] = name[iin];
 479       ++iin;
 480    }
 481    msg[fixed_message_ln + iin] = 0;
 482    png_error(png_ptr, msg);
 483 }
 484 #endif
 485 #endif
 486
 487 #ifdef PNG_SETJMP_SUPPORTED
 488 /* This API only exists if ANSI-C style error handling is used,
 489  * otherwise it is necessary for png_default_error to be overridden.
 490  */
 491 jmp_buf* PNGAPI
 492 png_set_longjmp_fn(png_structp png_ptr, png_longjmp_ptr longjmp_fn,
 493     size_t jmp_buf_size)
 494 {
 495    if (png_ptr == NULL || jmp_buf_size != png_sizeof(jmp_buf))
 496       return NULL;
 497
 498    png_ptr->longjmp_fn = longjmp_fn;
 499    return &png_ptr->longjmp_buffer;
 500 }
 501 #endif
 502
 503 /* This is the default error handling function.  Note that replacements for
 504  * this function MUST NOT RETURN, or the program will likely crash.  This
 505  * function is used by default, or if the program supplies NULL for the
 506  * error function pointer in png_set_error_fn().
 507  */
 508 static PNG_FUNCTION(void /* PRIVATE */,
 509 png_default_error,(png_structp png_ptr, png_const_charp error_message),
 510    PNG_NORETURN)
 511 {
 512 #ifdef PNG_CONSOLE_IO_SUPPORTED
 513 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
 514    /* Check on NULL only added in 1.5.4 */
 515    if (error_message != NULL && *error_message == PNG_LITERAL_SHARP)
 516    {
 517       /* Strip "#nnnn " from beginning of error message. */
 518       int offset;
 519       char error_number[16];
 520       for (offset = 0; offset<15; offset++)
 521       {
 522          error_number[offset] = error_message[offset + 1];
 523          if (error_message[offset] == ' ')
 524             break;
 525       }
 526
 527       if ((offset > 1) && (offset < 15))
 528       {
 529          error_number[offset - 1] = '\0';
 530          fprintf(stderr, "libpng error no. %s: %s",
 531              error_number, error_message + offset + 1);
 532          fprintf(stderr, PNG_STRING_NEWLINE);
 533       }
 534
 535       else
 536       {
 537          fprintf(stderr, "libpng error: %s, offset=%d",
 538              error_message, offset);
 539          fprintf(stderr, PNG_STRING_NEWLINE);
 540       }
 541    }
 542    else
 543 #endif
 544    {
 545       fprintf(stderr, "libpng error: %s", error_message ? error_message :
 546          "undefined");
 547       fprintf(stderr, PNG_STRING_NEWLINE);
 548    }
 549 #else
 550    PNG_UNUSED(error_message) /* Make compiler happy */
 551 #endif
 552    png_longjmp(png_ptr, 1);
 553 }
 554
 555 PNG_FUNCTION(void,PNGAPI
 556 png_longjmp,(png_structp png_ptr, int val),PNG_NORETURN)
 557 {
 558 #ifdef PNG_SETJMP_SUPPORTED
 559    if (png_ptr && png_ptr->longjmp_fn)
 560    {
 561 #  ifdef USE_FAR_KEYWORD
 562       {
 563          jmp_buf tmp_jmpbuf;
 564          png_memcpy(tmp_jmpbuf, png_ptr->longjmp_buffer, png_sizeof(jmp_buf));
 565          png_ptr->longjmp_fn(tmp_jmpbuf, val);
 566       }
 567
 568 #  else
 569    png_ptr->longjmp_fn(png_ptr->longjmp_buffer, val);
 570 #  endif
 571    }
 572 #endif
 573    /* Here if not setjmp support or if png_ptr is null. */
 574    PNG_ABORT();
 575 }
 576
 577 #ifdef PNG_WARNINGS_SUPPORTED
 578 /* This function is called when there is a warning, but the library thinks
 579  * it can continue anyway.  Replacement functions don't have to do anything
 580  * here if you don't want them to.  In the default configuration, png_ptr is
 581  * not used, but it is passed in case it may be useful.
 582  */
 583 static void /* PRIVATE */
 584 png_default_warning(png_structp png_ptr, png_const_charp warning_message)
 585 {
 586 #ifdef PNG_CONSOLE_IO_SUPPORTED
 587 #  ifdef PNG_ERROR_NUMBERS_SUPPORTED
 588    if (*warning_message == PNG_LITERAL_SHARP)
 589    {
 590       int offset;
 591       char warning_number[16];
 592       for (offset = 0; offset < 15; offset++)
 593       {
 594          warning_number[offset] = warning_message[offset + 1];
 595          if (warning_message[offset] == ' ')
 596             break;
 597       }
 598
 599       if ((offset > 1) && (offset < 15))
 600       {
 601          warning_number[offset + 1] = '\0';
 602          fprintf(stderr, "libpng warning no. %s: %s",
 603              warning_number, warning_message + offset);
 604          fprintf(stderr, PNG_STRING_NEWLINE);
 605       }
 606
 607       else
 608       {
 609          fprintf(stderr, "libpng warning: %s",
 610              warning_message);
 611          fprintf(stderr, PNG_STRING_NEWLINE);
 612       }
 613    }
 614    else
 615 #  endif
 616
 617    {
 618       fprintf(stderr, "libpng warning: %s", warning_message);
 619       fprintf(stderr, PNG_STRING_NEWLINE);
 620    }
 621 #else
 622    PNG_UNUSED(warning_message) /* Make compiler happy */
 623 #endif
 624    PNG_UNUSED(png_ptr) /* Make compiler happy */
 625 }
 626 #endif /* PNG_WARNINGS_SUPPORTED */
 627
 628 /* This function is called when the application wants to use another method
 629  * of handling errors and warnings.  Note that the error function MUST NOT
 630  * return to the calling routine or serious problems will occur.  The return
 631  * method used in the default routine calls longjmp(png_ptr->longjmp_buffer, 1)
 632  */
 633 void PNGAPI
 634 png_set_error_fn(png_structp png_ptr, png_voidp error_ptr,
 635     png_error_ptr error_fn, png_error_ptr warning_fn)
 636 {
 637    if (png_ptr == NULL)
 638       return;
 639
 640    png_ptr->error_ptr = error_ptr;
 641    png_ptr->error_fn = error_fn;
 642 #ifdef PNG_WARNINGS_SUPPORTED
 643    png_ptr->warning_fn = warning_fn;
 644 #else
 645    PNG_UNUSED(warning_fn)
 646 #endif
 647 }
 648
 649
 650 /* This function returns a pointer to the error_ptr associated with the user
 651  * functions.  The application should free any memory associated with this
 652  * pointer before png_write_destroy and png_read_destroy are called.
 653  */
 654 png_voidp PNGAPI
 655 png_get_error_ptr(png_const_structp png_ptr)
 656 {
 657    if (png_ptr == NULL)
 658       return NULL;
 659
 660    return ((png_voidp)png_ptr->error_ptr);
 661 }
 662
 663
 664 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
 665 void PNGAPI
 666 png_set_strip_error_numbers(png_structp png_ptr, png_uint_32 strip_mode)
 667 {
 668    if (png_ptr != NULL)
 669    {
 670       png_ptr->flags &=
 671          ((~(PNG_FLAG_STRIP_ERROR_NUMBERS |
 672          PNG_FLAG_STRIP_ERROR_TEXT))&strip_mode);
 673    }
 674 }
 675 #endif
 676 #endif /* PNG_READ_SUPPORTED || PNG_WRITE_SUPPORTED */