TIFFWARNING(3tiff) LibTIFF TIFFWARNING(3tiff)

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.

Please refer to TIFFOpenOptions for how to setup the
application-specific handler introduced with libtiff 4.5.

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 further warning handler functions within TIFFWarningExtR():

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

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

SEE ALSO

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

AUTHOR

LibTIFF contributors

COPYRIGHT

1988-2025, LibTIFF contributors

4.7 March 7, 2026 TIFFWARNING(3tiff)