On 18 Jul 2024, at 16:21, Ramiro Polla wrote:
> On Thu, Jul 18, 2024 at 3:41 PM Stefan Oltmanns via ffmpeg-devel > <[email protected]> wrote: >> Am 18.07.24 um 15:04 schrieb Ramiro Polla: >>>>>> [...] >>>>>> >>>>>> +static VSScriptLibrary vs_script_library; >>>>> >>>>> Does vs_script_library have to be a global? >>>>> >>>> >>>> I think it has to: ffmpeg allows multiple input files, in case you open >>>> two VapourSynth files you want to load the Library only once. >>> >>> It should be possible to dlopen()/LoadLibrary() multiple times, and >>> the library only gets really unloaded after the last call to >>> dlclose()/FreeLibrary(). In that case you could move that struct to >>> the context. If it's unavoidable to keep the global, at least add some >>> locks to access it. >> >> Yes, that should be possible. I did a quick search at it seems that >> dlopen()/LoadLibrary() is smart and will not open the same library >> multiple times, but return the same pointer. >> As dlclose won't be used anymore when removing the atexit handler, that >> is not an issue at all. > > dlclose() will have to be called at some point (i.e.: in read_close). > >>>> This is exactly how it's done for AviSynth. >>> >>> Perhaps AviSynth is not the best example to follow :) >>> >>>>>> + >>>>>> +static int vs_atexit_called = 0; >>>>>> + >>>>>> +static av_cold void vs_atexit_handler(void); >>>>>> + >>>>>> +#ifdef _WIN32 >>>>>> +static av_cold char* get_vs_script_dll_name(void) { >>>>>> + LONG r; >>>>>> + WCHAR vss_path[512]; >>>>>> + char *vss_path_utf8; >>>>>> + DWORD buf_size = sizeof(vss_path) - 2; >>>>>> + r = RegGetValueW(HKEY_CURRENT_USER, L"SOFTWARE\\VapourSynth", >>>>>> + L"VSScriptDLL", RRF_RT_REG_SZ, NULL, >>>>>> + &vss_path, &buf_size); >>>>>> + if (r == ERROR_SUCCESS && wchartoutf8(vss_path, &vss_path_utf8) >>>>>> == 0) >>>>>> + return vss_path_utf8; >>>>>> + r = RegGetValueW(HKEY_LOCAL_MACHINE, L"SOFTWARE\\VapourSynth", >>>>>> + L"VSScriptDLL", RRF_RT_REG_SZ, NULL, >>>>>> + &vss_path, &buf_size); >>>>>> + if (r == ERROR_SUCCESS && wchartoutf8(vss_path, &vss_path_utf8) >>>>>> == 0) >>>>>> + return vss_path_utf8; >>>>>> + if (wchartoutf8(L"VSScript.dll", &vss_path_utf8) == 0) >>>>>> + return vss_path_utf8; >>>>>> + return 0; >>>>>> +} >>>>>> +#endif >>>>> >>>>> Don't fetch the path on the registry on Windows. The user should set the >>>>> path outside of FFmpeg. >>>> >>>> How exactly should the user do that? Additional option to ffmpeg? >>> >>> By making sure the libraries are accessible in the PATH environment >>> variable. For example by adding the VapourSynth path to the PATH >>> environment variable, or overriding PATH on the call to FFmpeg on a >>> script. Either way that's outside the scope of FFmpeg. >> >> Well, the DLL directory is added to PATH by the VapourSynth installer, >> but for safety reasons ffmpeg explictly tells the LoadLibrary function >> to only search the application directory and system32, quote from >> w32dlfcn.h: >> >>> /** >>> * Safe function used to open dynamic libs. This attempts to improve >>> program security >>> * by removing the current directory from the dll search path. Only dll's >>> found in the >>> * executable or system directory are allowed to be loaded. >>> * @param name The dynamic lib name. >>> * @return A handle to the opened lib. >>> */ >> So ffmpeg prevents that solution on purpose. Or should that behavior be >> changed in the w32dlfcn.h? > > Oh, bummer. I would expect that overriding the PATH environment > variable would work kind of like how LD_LIBRARY_PATH works on Linux. I > don't know why that was changed. I don't really follow what goes on in > Windowsland anymore. Does anyone else care to comment on this? Martin, > maybe? IIRC this is done to prevent DLL injection attacks https://learn.microsoft.com/en-us/windows/win32/dlls/dynamic-link-library-security > > Ramiro > _______________________________________________ > ffmpeg-devel mailing list > [email protected] > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel > > To unsubscribe, visit link above, or email > [email protected] with subject "unsubscribe". _______________________________________________ ffmpeg-devel mailing list [email protected] https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email [email protected] with subject "unsubscribe".
