---
name: "TIFFWarning"
section: "3tiff"
platform: "linux"
package: "libtiff-dev"
version: "4.7.0-3+deb13u3"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/TIFFWarning/3tiff"
---

# TIFFWarning(3tiff)

library warning interface

## 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

1988-2022, LibTIFF contributors