TIFFWARNING(3tiff)

✨ TIFFWARNING ✨ (that's the 3tiff manual btw 💖)

okay bestie, so this is the LibTIFF page about the library's warning interface. Not errors, not drama — just lil "hey heads up" messages. Let's get into it 🫶

---

🌸 SYNOPSIS 🌸

like, here's the whole vibe in code form:

#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() calls the library-wide warning handler function, which (normally, like default behaviour) writes a warning message out to stderr. The fmt parameter is a printf() format string, and you can pass literally any number of extra arguments to it. The module parameter gets read as a string that, if it's non-zero, should be printed before the message — it's typically used to identify which software module the warning got detected in. iykyk 🎀

If your app wants to take control when a warning happens, use TIFFSetWarningHandler() to override the default warning handler. And yes, you can install a NULL (0) warning handler function to just suppress warning messages entirely — no thoughts, head empty, warnings gone 💀

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. slay 💅

TIFFWarningExt() hands you a file handle as a parameter. Inside libtiff, TIFFWarningExt() gets 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 set up with TIFFSetWarningHandlerExt(). ✨

TIFFWarningExtR() (introduced with libtiff 4.5) gets called with its TIFF handle, so it gives you access to a per-TIFF handle (re-entrant) warning handler. Which means: for different TIFF handles, you can set up different warning handlers. main character energy fr fr 👑 This application-specific handler can be set up when a TIFF file is opened with one of these functions:

• TIFFOpenExt()
• TIFFOpenWExt()
• TIFFFdOpenExt()
• TIFFClientOpenExt()

Furthermore, a custom defined data structure user_data for the warning handler can be given along. 🦋

Please refer to TIFFOpenOptions for how to set up 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, then TIFFWarningHandler() and then TIFFWarningHandlerExt() are called. From libtiff 4.5 onwards, TIFFWarningExtR() is used within the libtiff library. 🔥

---

💫 RETURN VALUES 💫

TIFFSetWarningHandler() and TIFFSetWarningHandlerExt() return a reference to the previous warning handler function. (yes, so you can put it back later, iconic behaviour 💅)

TIFFWarningHandlerExtR() returns an integer as a "stop" to control the call of further 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)
• TIFFOpenOptions
• libtiff (3tiff)
• printf (3)

---

👑 AUTHOR 👑

LibTIFF contributors 💖

---

🌈 COPYRIGHT 🌈

1988-2025, LibTIFF contributors

---

okay that's the whole page bestie, no cap, nothing skipped 🫶 and just so you know the full legal-ese footer energy: this is from LibTIFF 4.7, dated Jun 27, 2026, and it's the TIFFWARNING(3tiff) page. periodt. 💅✨🎀