openjdk/jdk · warning

libpng warning: %s

Error message

libpng warning: %s

What it means

libpng's default warning handler inside the JDK splashscreen: prints 'libpng warning: <message>' for conditions libpng considers non-fatal (e.g. a chunk with bad CRC that will be skipped, extra zero bytes at end of file, sRGB profile mismatches). Decoding continues; the longjmp is only taken by the error path, not here.

Source

Thrown at src/java.desktop/share/native/libsplashscreen/libpng/pngerror.c:732

    * choice is to terminate the whole process (or maybe the thread); to do
    * this the ANSI-C abort() function is used unless a different method is
    * implemented by overriding the default configuration setting for
    * PNG_ABORT().
    */
   PNG_ABORT();
}

#ifdef PNG_WARNINGS_SUPPORTED
/* This function is called when there is a warning, but the library thinks
 * it can continue anyway.  Replacement functions don't have to do anything
 * here if you don't want them to.  In the default configuration, png_ptr is
 * not used, but it is passed in case it may be useful.
 */
static void /* PRIVATE */
png_default_warning(png_const_structrp png_ptr, png_const_charp warning_message)
{
#ifdef PNG_CONSOLE_IO_SUPPORTED
   fprintf(stderr, "libpng warning: %s", warning_message);
   fprintf(stderr, PNG_STRING_NEWLINE);
#else
   PNG_UNUSED(warning_message) /* Make compiler happy */
#endif
   PNG_UNUSED(png_ptr) /* Make compiler happy */
}
#endif /* WARNINGS */

/* This function is called when the application wants to use another method
 * of handling errors and warnings.  Note that the error function MUST NOT
 * return to the calling routine or serious problems will occur.  The return
 * method used in the default routine calls longjmp(png_ptr->jmp_buf_ptr, 1)
 */
void PNGAPI
png_set_error_fn(png_structrp png_ptr, png_voidp error_ptr,
    png_error_ptr error_fn, png_error_ptr warning_fn)
{
   if (png_ptr == NULL)

View on GitHub (pinned to 88dfb74bbe)

Solutions

1. Run 'pngcheck -v image.png' and fix the specific chunk it flags
2. Strip ancillary chunks: 'pngcrush -brute in.png out.png' or 'optipng -strip all' produces a clean file
3. Re-export from the original source rather than round-tripping through editors that mutate profiles
4. Ignore it — warnings do not stop splash rendering

// CI step: fail on any pngcheck warning
// pngcheck -vw splash.png || echo "fix warnings before release"

When it happens

Trigger: Loading a splash PNG that has a recoverable defect: incorrect but ignorable chunk CRC, trailing garbage after IEND, an iCCP/sRGB chunk with an odd profile, or an interlaced file with benign issues. Each such chunk makes libpng emit this warning during splash image parsing.

Common situations: Images passed through multiple tools that append metadata; PNGs saved by older Photoshop/GIMP with non-standard iCCP profiles; files with trailing newline bytes appended by text-mode transfers. Cosmetic: the splash still renders.

Related errors

• libpng error: %s
• %s\n
• Could not create SplashScreen thread, error number:%d\n
• Error: Out of memory in ADLC\n
• JVM caught ASAN Error

AI-assisted analysis of openjdk/jdk@88dfb74bbe (2026-08-14). Data as JSON: /api/errors/3d72bbe271992bf0. Report an issue: GitHub.