Yalantis/uCrop · warning

cimg::system() : Command

Error message

cimg::system() : Command '%s' (module name '%s) failed with error %lu: %s

What it means

cimg::system() runs an external shell command; on Windows it uses system()/popen-style helpers and reports failure via GetLastError(). When the command returns nonzero, CImg emits this warning with the OS error message from FormatMessageA and returns -1 instead of throwing. It signals that the requested external program could not be launched or executed by the OS.

Solutions

1. Verify the command's executable is installed and present in PATH on the target Windows machine
2. Print/inspect the exact command string being built (check quoting of paths with spaces)
3. Handle the -1 return value instead of assuming success, and provide a fallback path that does not shell out
4. Run the same command manually in cmd.exe to see the underlying OS error

Example fix

// before
cimg::system("convert in.png out.jpg", true);
// after
const int res = cimg::system("\"C:\\Program Files\\ImageMagick\\convert.exe\" in.png out.jpg", true);
if (res != 0) { /* fallback: use CImg's native load/save instead */ }

// before shelling out
const char* cmd = "convert";
if (!cmd || !*cmd) { fprintf(stderr, "no command configured\n"); return; }
// On Windows, optionally check availability:
// cimg::system("where convert >nul 2>&1") != 0 -> command missing

When it happens

Trigger: Calling cimg::system() (directly or indirectly via CImg features that shell out, e.g. external viewer/convert helpers) on Windows when the command binary is missing from PATH, is misspelled, or exits with a nonzero status; module_name or command may even be null as handled in the source.

Common situations: Windows deployments where ImageMagick/ffmpeg or a viewer executable is not installed or not on PATH; quoting problems with paths containing spaces; environment differences between dev and target machines.

Related errors

• assign(): Invalid assignment request of shared instance from
• assign(): Shared image instance has overlapping memory.
• at(): Empty instance.
• atN(): Empty instance.
• atNX(): Empty instance.

AI-assisted analysis of Yalantis/uCrop@f788b534b4 (2026-09-08). Data as JSON: /api/errors/b3b2fd61b21a4e4c. Report an issue: GitHub.

Appendix: source

Thrown at ucrop/src/main/jni/CImg.h:6022

      std::memset(&si,0,sizeof(STARTUPINFO));
      GetStartupInfoA(&si);
      si.cb = sizeof(si);
      si.wShowWindow = SW_HIDE;
      si.dwFlags |= SW_HIDE | STARTF_USESHOWWINDOW;
      const BOOL res = CreateProcessA((LPCSTR)module_name,(LPSTR)command,0,0,FALSE,0,0,0,&si,&pi);
      if (res) {
        WaitForSingleObject(pi.hProcess,INFINITE);
        CloseHandle(pi.hThread);
        CloseHandle(pi.hProcess);
        return 0;
      } else {
        char* lpMsgBuf;

        // Get the error message.
        DWORD errorCode = GetLastError();
        FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
                       0,errorCode,MAKELANGID(LANG_NEUTRAL,SUBLANG_DEFAULT),(LPSTR)&lpMsgBuf,0,0);
        cimg::warn("cimg::system() : Command '%s' (module name '%s) failed with error %lu: %s",
                   module_name==0?"(null)":module_name,
                   command==0?"(null)":command,
                   errorCode,lpMsgBuf);
        return -1;
      }
#else
      return std::system(command);
#endif
#endif
    }

    //! Return a reference to a temporary variable of type T.
    template<typename T>
    inline T& temporary(const T&) {
      static T temp;
      return temp;
    }

View on GitHub (pinned to f788b534b4)