[vlc-devel] [PATCH 1/2] [RFC] core: add a function to load a system shared library

[Steve Lhomme]

On Thu, Mar 9, 2017 at 11:57 AM, Thomas Guillem <thomas at gllm.fr> wrote:
>
>
> On Thu, Mar 9, 2017, at 11:50, Steve Lhomme wrote:
>> it cannot be loaded from anywhere but the system
>> ---
>>  include/vlc_modules.h | 13 ++++++++++++
>>  src/libvlccore.sym    |  1 +
>>  src/missing.c         |  7 +++++++
>>  src/network/udp.c     |  3 ++-
>>  src/text/url.c        |  2 +-
>>  src/win32/plugin.c    | 57
>>  +++++++++++++++++++++++++++++++++++++++++++++++++++
>>  6 files changed, 81 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/vlc_modules.h b/include/vlc_modules.h
>> index 7f45217969..ec5c69c36a 100644
>> --- a/include/vlc_modules.h
>> +++ b/include/vlc_modules.h
>> @@ -65,6 +65,19 @@ VLC_API const char * module_get_capability( const
>> module_t *m ) VLC_USED;
>>  VLC_API int module_get_score( const module_t *m ) VLC_USED;
>>  VLC_API const char * module_gettext( const module_t *, const char * )
>>  VLC_USED;
>>
>> +#ifdef _WIN32
>> +typedef HMODULE vlc_lib_handle_t;
>> +#else
>> +typedef void *vlc_lib_handle_t;
>> +#endif
>
> As HMODULE is a PVOID, I would prefer to always return a void * here.

I forced the HMODULE because in C++ code it complained about a cast
from void* to HMODULE.

>> +
>> +/**
>> + * Load a system library (DLL) in memory.
>> + *
>> + * @param libname the name of system library to load.
>> + */
>> +VLC_API vlc_lib_handle_t vlc_load_syslib(const char *libname);
>> +
>>  VLC_USED static inline module_t *module_get_main (void)
>>  {
>>      return module_find ("core");
>> diff --git a/src/libvlccore.sym b/src/libvlccore.sym
>> index 57c83495a3..1c0e6ee0a3 100644
>> --- a/src/libvlccore.sym
>> +++ b/src/libvlccore.sym
>> @@ -462,6 +462,7 @@ us_vasprintf
>>  vlc_close
>>  vlc_fopen
>>  utf8_fprintf
>> +vlc_load_syslib
>>  vlc_loaddir
>>  vlc_lstat
>>  vlc_mkdir
>> diff --git a/src/missing.c b/src/missing.c
>> index c76e99a4bc..99670c8e95 100644
>> --- a/src/missing.c
>> +++ b/src/missing.c
>> @@ -442,3 +442,10 @@ update_release_t *update_GetRelease(update_t *u)
>>      vlc_assert_unreachable();
>>  }
>>  #endif /* !UPDATE_CHECK */
>> +
>> +#ifndef _WIN32
>> +void *vlc_load_syslib(const char *libname)
>> +{
>> +    return NULL;
>> +}
>> +#endif
>> diff --git a/src/network/udp.c b/src/network/udp.c
>> index d098fb1425..bf3dc2266a 100644
>> --- a/src/network/udp.c
>> +++ b/src/network/udp.c
>> @@ -36,6 +36,7 @@
>>  #include <errno.h>
>>  #include <assert.h>
>>
>> +#include <vlc_modules.h>
>>  #include <vlc_network.h>
>>
>>  #ifdef _WIN32
>> @@ -105,7 +106,7 @@ static int net_SetupDgramSocket (vlc_object_t *p_obj,
>> int fd,
>>       * receive buffer if that isn't present
>>       */
>>  #if (_WIN32_WINNT < _WIN32_WINNT_WIN8)
>> -    HINSTANCE h_Network = LoadLibrary(TEXT("Windows.Networking.dll"));
>> +    HMODULE h_Network = vlc_load_syslib("Windows.Networking.dll");
>>      if( (h_Network == NULL) ||
>>          (GetProcAddress( h_Network, "SetSocketMediaStreamingMode" ) ==
>>          NULL ) )
>>      {
>> diff --git a/src/text/url.c b/src/text/url.c
>> index 1b602b599e..682ea9665d 100644
>> --- a/src/text/url.c
>> +++ b/src/text/url.c
>> @@ -837,7 +837,7 @@ char *vlc_uri_fixup(const char *str)
>>  #  define IDN_ALLOW_UNASSIGNED 0x01
>>  static int IdnToAscii(DWORD flags, LPCWSTR str, int len, LPWSTR buf, int
>>  size)
>>  {
>> -    HMODULE h = LoadLibrary(_T("Normaliz.dll"));
>> +    HMODULE h = vlc_load_syslib("Normaliz.dll");
>>      if (h == NULL)
>>      {
>>          errno = ENOSYS;
>> diff --git a/src/win32/plugin.c b/src/win32/plugin.c
>> index 1a65521fca..6bade68fbc 100644
>> --- a/src/win32/plugin.c
>> +++ b/src/win32/plugin.c
>> @@ -29,6 +29,7 @@
>>
>>  #include <vlc_common.h>
>>  #include <vlc_charset.h>
>> +#include <vlc_modules.h>
>>  #include "modules/modules.h"
>>  #include <windows.h>
>>  #include <wchar.h>
>> @@ -133,3 +134,59 @@ void *module_Lookup( module_handle_t handle, const
>> char *psz_function )
>>  {
>>      return (void *)GetProcAddress( handle, (char *)psz_function );
>>  }
>> +
>> +HMODULE vlc_load_syslib(const char *libname)
>> +{
>> +    HMODULE module;
>> +    bool has_KB2533623 = true;
>> +    TCHAR *tlibname;
>> +#if (_WIN32_WINNT < _WIN32_WINNT_WIN8)
>> +    /* check for KB2533623 */
>> +    if (GetProcAddress(GetModuleHandle(TEXT("kernel32.dll")),
>> +                                       "SetDefaultDllDirectories") ==
>> NULL)
>> +        has_KB2533623 = false;
>> +#endif
>> +
>> +#ifdef UNICODE
>> +    tlibname = ToWide(libname);
>> +    if (unlikely(tlibname==NULL))
>> +        return NULL;
>> +#else
>> +    tlibname = libname;
>> +#endif
>> +
>> +    if (false && has_KB2533623)
>> +        module = LoadLibraryEx(tlibname, NULL,
>> LOAD_LIBRARY_SEARCH_SYSTEM32);
>> +    else
>> +    {
>> +        /* force the path of the DLL inside system32 */
>> +        DWORD systemLen = GetSystemDirectory(NULL, 0);
>> +        if (systemLen) {
>> +            systemLen += 1 + _tcslen(tlibname);
>> +            TCHAR *sysdir = malloc(systemLen * sizeof(*sysdir));
>> +            if (likely(sysdir!=NULL)) {
>> +                if (GetSystemDirectory(sysdir, systemLen)) {
>> +                    _tcsncat(sysdir, _T("\\"), systemLen);
>> +                    _tcsncat(sysdir, tlibname, systemLen);
>> +
>> +#ifdef UNICODE
>> +                    free(tlibname);
>> +#endif
>> +                    tlibname = sysdir;
>> +                }
>> +            }
>> +        }
>> +
>> +        module = LoadLibrary(tlibname);
>> +
>> +        if ((const char*)tlibname != libname) {
>> +            free(tlibname);
>> +            tlibname = NULL; /* no double free on unicode */
>> +        }
>> +    }
>> +
>> +#ifdef UNICODE
>> +    free(tlibname);
>> +#endif
>> +    return module;
>> +}
>> --
>> 2.11.1
>>
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