NAME

       TIFFWarning - library warning interface

SYNOPSIS

          #include <tiffio.h>
          #include <stdarg.h>

       void TIFFWarning(const char *module, const char *fmt, ...)

       void TIFFWarningExt(thandle_t fd, const char *module, const char *fmt, ...)

       void TIFFWarningExtR(TIFF *tif, const char *module, const char *fmt, ...)

       typedef void (*TIFFWarningHandler)(const char *module, const char *fmt, va_list ap)

       typedef void (*TIFFWarningHandlerExt)(thandle_t fd, const char *module, const char *fmt, va_list ap)

       typedef int (*TIFFWarningHandlerExtR)(TIFF *tif, void *user_data, const char *module, const char *fmt,
       va_list ap)

       TIFFWarningHandler TIFFSetWarningHandler(TIFFWarningHandler handler)

       TIFFWarningHandlerExt TIFFSetWarningHandlerExt(TIFFWarningHandlerExt handler)

DESCRIPTION

       TIFFWarning()  invokes the library-wide warning handler function to (normally) write a warning message to
       the stderr.  The fmt parameter is a printf() format string, and any number arguments can be supplied. The
       module parameter is interpreted as a string that, if non-zero, should be printed before the  message;  it
       typically is used to identify the software module in which a warning is detected.

       Applications  that desire to capture control in the event of a warning should use TIFFSetWarningHandler()
       to override the default warning handler. A NULL (0) warning handler function may be installed to suppress
       warning messages.

       Two more  application-specific  warning  handler  callbacks  are  available,  each  with  different  call
       parameters  and  passing  parameters  to the handler.  Each handler is also linked with a warning message
       function, i.e.  TIFFWarningExt() and TIFFWarningExtR() if the application intends  to  call  the  handler
       with those extended parameters.

       TIFFWarningExt()  provides a file handle as parameter.  Within libtiff TIFFWarningExt() is called passing
       tif->tif_clientdata  as  fd,  which  represents  the   TIFF   file   handle   (file   descriptor).    The
       application-specific     and    library-wide    handler    for    TIFFWarningExt()    is    setup    with
       TIFFSetWarningHandlerExt().

       TIFFWarningExtR() (introduced with libtiff 4.5) is called with its TIFF handle and thus  provides  access
       to  a  per-TIFF  handle  (re-entrant)  warning  handler. That means for different TIFF handles, different
       warning handlers can be setup. This application-specific handler can be setup when a TIFF file is  opened
       with    one   of   the   following   functions:   TIFFOpenExt(),   TIFFOpenWExt(),   TIFFFdOpenExt()   or
       TIFFClientOpenExt().  Furthermore, a custom defined data structure user_data for the warning handler  can
       be given along.

NOTE

       Both functions TIFFWarning() and TIFFWarningExt() each attempt to call both handler functions if they are
       defined.   First TIFFWarningHandler() is called and then TIFFWarningHandlerExt().  However, TIFFWarning()
       passes a "0" as a file handle to TIFFWarningHandlerExt().

       TIFFWarningExtR()  tries  first   to   call   the   per-TIFF   handle   defined   warning   handler.   If
       TIFFWarningHandlerExtR()    is    not    defined    or   returns   0,   TIFFWarningHandler()   and   then
       TIFFWarningHandlerExt() are called. From libtiff 4.5 onwards TIFFWarningExtR() is used within the libtiff
       library.

RETURN VALUES

       TIFFSetWarningHandler() and TIFFSetWarningHandlerExt()  returns  a  reference  to  the  previous  warning
       handler function.

       TIFFWarningHandlerExtR()  returns  an  integer  as  "stop" to control the call of furhter warning handler
       functions within TIFFWarningExtR():

          • 0: both functions TIFFWarningHandler() and TIFFWarningHandlerExt() are called.

          • non-zero: no further warning message function is called.

SEE ALSO

       TIFFError (3tiff), TIFFOpen (3tiff), libtiff (3tiff), printf (3)

AUTHOR

       LibTIFF contributors

COPYRIGHT

       1988-2025, LibTIFF contributors

4.5                                               Sep 24, 2025                                TIFFWARNING(3tiff)