Yalantis/uCrop · error · CImgArgumentException

cimg::load_network(): Specified URL is (null).

Error message

cimg::load_network(): Specified URL is (null).

What it means

cimg::load_network() downloads a file from a URL to a local path (via libcurl, wget, or curl). The library throws this CImgArgumentException when the url pointer itself is null, because no download can be started without an address. It is the first null-check guard in the function.

Source

Thrown at ucrop/src/main/jni/CImg.h:70061

      return f_type;
    }

    //! Load file from network as a local temporary file.
    /**
       \param url URL of the filename, as a C-string.
       \param[out] filename_local C-string containing the path to a local copy of \c filename.
       \param timeout Maximum time (in seconds) authorized for downloading the file from the URL.
       \param try_fallback When using libcurl, tells using system calls as fallbacks in case of libcurl failure.
       \param referer Referer used, as a C-string.
       \param user_agent User agent used, as a C-string.
       \return Value of \c filename_local.
       \note Use the \c libcurl library, or the external binaries \c wget or \c curl to perform the download.
    **/
    inline char *load_network(const char *const url, char *const filename_local,
                              const unsigned int timeout, const bool try_fallback,
                              const char *const referer, const char *const user_agent) {
      if (!url)
        throw CImgArgumentException("cimg::load_network(): Specified URL is (null).");
      if (!filename_local)
        throw CImgArgumentException("cimg::load_network(): Specified destination string is (null).");
      if (!network_mode())
        throw CImgIOException("cimg::load_network(): Loading files from network is disabled.");

      const char *const __ext = cimg::split_filename(url), *const _ext = (*__ext && __ext>url)?__ext - 1:__ext;
      CImg<char> ext = CImg<char>::string(_ext);
      *filename_local = 0;
      if (ext._width>16 || !cimg::strncasecmp(ext,"cgi",3)) *ext = 0;
      else cimg::strwindows_reserved(ext);
      do {
        cimg_snprintf(filename_local,256,"%s%c%s%s",
                      cimg::temporary_path(),cimg_file_separator,cimg::filenamerand(),ext._data);
      } while (cimg::path_exists(filename_local));

#ifdef cimg_use_curl
      const unsigned int omode = cimg::exception_mode();
      cimg::exception_mode(0);

View on GitHub (pinned to f788b534b4)

Solutions

1. Pass a valid, non-null URL string to load_network.
2. Check the URL variable for null/empty before calling; fall back to a default URL or fail fast with a clear message.
3. If the URL comes from config/JNI, validate at the boundary (non-empty, starts with http:// or https://).
4. Catch CImgArgumentException around the call to convert it into a handled error path.

Example fix

// before
img.load_network(url, localPath); // url may be NULL
// after
if (url && *url) img.load_network(url, localPath);
else fprintf(stderr, "no URL configured for remote image");

bool isValidUrl(const char *u) { return u && *u && (strncmp(u, "http://", 7) == 0 || strncmp(u, "https://", 8) == 0); }

bool nonEmptyString(const char *s) { return s != nullptr && *s != '\0'; }

try { img.load_network(url, local, 30, true, 0, 0); } catch (const CImgArgumentException &e) { fprintf(stderr, "bad argument for load_network: %s", e.what()); }

When it happens

Trigger: Calling cimg::load_network(NULL, dest, ...) directly, or via CImg<T>::load_network/load with a filename that resolved to a null pointer (e.g. from an unset config value or a failed string conversion).

Common situations: Fetching remote image templates where the URL config key is missing; JNI code passing a null string from Java; refactored code where the URL variable was removed or conditionally assigned.

Related errors

• cimg::load_network(): Specified destination string is (null)
• load(): Specified filename is (null).
• load_ascii(): Specified filename is (null).
• load_dlm(): Specified filename is (null).
• load_bmp(): Specified filename is (null).

AI-assisted analysis of Yalantis/uCrop@f788b534b4 (2026-09-08). Data as JSON: /api/errors/d75d75d493567aa5. Report an issue: GitHub.