Yalantis/uCrop · warning

cimg::fclose(): Error code

Error message

cimg::fclose(): Error code %d returned during file closing.

What it means

cimg::fclose() wraps std::fclose() and warns when the close call returns a nonzero error code, meaning buffered data may not have been flushed and the file was not closed properly. It is a non-fatal diagnostic; the return code is still propagated to the caller.

Solutions

1. Check the return value of cimg::fclose() and treat nonzero as a save failure (the file may be corrupt)
2. Check free disk space and medium health on the target volume
3. Check for prior write errors (ferror) before closing, and retry the save
4. On Windows, ensure no other process holds the file open

Example fix

// before
img.save("out.bmp");
cimg::fclose(file);
// after
if (cimg::fclose(file) != 0) {
  std::fprintf(stderr, "file close failed - output may be incomplete\n");
}

// before closing
if (file && !std::ferror(file)) {
  int r = cimg::fclose(file);
  if (r != 0) fprintf(stderr, "close failed (%d), output may be corrupt\n", r);
}

When it happens

Trigger: Calling cimg::fclose() on a real FILE* (not stdin/stdout/null) when the underlying close/flush fails — e.g. disk full, medium removed, or the stream is already in an error state after a prior failed write.

Common situations: Writing large images to a full disk or removable drive; network/USB storage dropping mid-write; ignoring earlier write errors so fclose also fails at flush time.

Related errors

• cimg::fclose(): Specified file is (null).
• cimg::fempty(): Specified filename is (null).
• cimg::fopen(): Failed to open file
• cimg::fopen(): File ' ', specified mode is (null).
• cimg::fopen(): Specified file path is (null).

AI-assisted analysis of Yalantis/uCrop@f788b534b4 (2026-09-08). Data as JSON: /api/errors/36d68d74ccb732f2. Report an issue: GitHub.

Appendix: source

Thrown at ucrop/src/main/jni/CImg.h:7584

#endif
      } else res = cimg::std_fopen(path,mode);
      if (!res) throw CImgIOException("cimg::fopen(): Failed to open file '%s' with mode '%s'.",
                                      path,mode);
      return res;
    }

    //! Close a file.
    /**
       \param file File to close.
       \return \c 0 if file has been closed properly, something else otherwise.
       \note Same as <tt>std::fclose()</tt> but display a warning message if
       the file has not been closed properly.
    **/
    inline int fclose(std::FILE *file) {
      if (!file) { warn("cimg::fclose(): Specified file is (null)."); return 0; }
      if (file==cimg::_stdin(false) || file==cimg::_stdout(false)) return 0;
      const int errn = std::fclose(file);
      if (errn!=0) warn("cimg::fclose(): Error code %d returned during file closing.",
                        errn);
      return errn;
    }

    //! Version of 'fseek()' that supports >=64bits offsets everywhere (for Windows).
    inline int fseek(FILE *stream, cimg_long offset, int origin) {
#if defined(WIN64) || defined(_WIN64) || defined(__WIN64__)
      return _fseeki64(stream,(__int64)offset,origin);
#else
      return std::fseek(stream,offset,origin);
#endif
    }

    //! Version of 'ftell()' that supports >=64bits offsets everywhere (for Windows).
    inline cimg_long ftell(FILE *stream) {
#if defined(WIN64) || defined(_WIN64) || defined(__WIN64__)
      return (cimg_long)_ftelli64(stream);
#else

View on GitHub (pinned to f788b534b4)