Implement support for dlsym() with RTLD_DEFAULT and RTLD_NEXT

dlsym() with RTLD_DEFAULT handle behaves in same way like with global handle
returned by dlopen() with NULL file name.

dlsym() with RTLD_NEXT handle search for next loaded module which provides
specified symbol. "Next" means module which in EnumProcessModules() result
after the module which called dlsym().

To get caller function of dlsym() use _ReturnAddress() intrinsic. To get
module where is caller function use the fact that HMODULE is the same value
as the module's base address.

When compiling under gcc, defines _ReturnAddress() macro via gcc's builtin
as it does not provide MSC's specific _ReturnAddress() intrinsic.

Added tests demonstrate that both RTLD_DEFAULT and RTLD_NEXT are working as
expected.

1 files changed, 60 insertions, 0 deletions

diff --git a/test.c b/test.c
index 10c655e..814aca1 100644
--- a/test.c
+++ b/test.c
@@ -73,10 +73,13 @@
 int main()

 {

     void *global;

+    void *library2;

     void *library;

     char *error;

     int (*function)( void );

+    int (*function2_from_library2)( void );

     size_t (*fwrite_local) ( const void *, size_t, size_t, FILE * );

+    size_t (*fputs_default) ( const char *, FILE * );

     int (*nonexistentfunction)( void );

     int ret;

     HMODULE library3;

@@ -90,6 +93,16 @@ int main()
     _CrtSetReportFile(_CRT_ASSERT, _CRTDBG_FILE_STDOUT);

 #endif

 

+    library2 = dlopen( "testdll2.dll", RTLD_GLOBAL );

+    if( !library2 )

+    {

+        error = dlerror( );

+        printf( "ERROR\tCould not open library2 globally: %s\n", error ? error : "" );

+        RETURN_ERROR; 

+    }

+    else

+        printf( "SUCCESS\tOpened library2 globally: %p\n", library2 );

+

     library = dlopen( "testdll.dll", RTLD_GLOBAL );

     if( !library )

     {

@@ -127,6 +140,22 @@ int main()
     fwrite_local(hello_world,sizeof(char),strlen(hello_world),stderr);

     fflush(stderr);

 

+    fputs_default = dlsym(RTLD_DEFAULT, "fputs");

+    if (!fputs_default)

+    {

+        error = dlerror();

+        printf("ERROR\tCould not get symbol from default handle: %s\n",

+            error ? error : "");

+        CLOSE_LIB;

+        CLOSE_GLOBAL;

+        RETURN_ERROR;

+    }

+    else

+        printf("SUCCESS\tGot symbol from default handle: %p\n", fputs_default);

+    char * hello_world_fputs = "Hello world from default fputs!\n";

+    fputs_default(hello_world_fputs, stderr);

+    fflush(stderr);

+

     function = dlsym( library, "function" );

     if( !function )

     {

@@ -142,6 +171,27 @@ int main()
 

     RUNFUNC;

 

+    function2_from_library2 = dlsym( library2, "function2" );

+    if( !function2_from_library2 )

+    {

+        error = dlerror( );

+        printf( "ERROR\tCould not get symbol from library2 handle: %s\n",

+                error ? error : "" );

+        CLOSE_LIB;

+        CLOSE_GLOBAL;

+        RETURN_ERROR;

+    }

+    else

+        printf( "SUCCESS\tGot symbol from library2 handle: %p\n", function2_from_library2 );

+

+    ret = function2_from_library2 ();

+    if( ret != 2 )

+    {

+        CLOSE_LIB;

+        CLOSE_GLOBAL;

+        RETURN_ERROR;

+    }

+

     nonexistentfunction = dlsym( library, "nonexistentfunction" );

     if( nonexistentfunction )

     {

@@ -197,6 +247,16 @@ int main()
     else

         printf( "SUCCESS\tClosed library.\n" );

 

+    ret = dlclose( library2 );

+    if( ret )

+    {

+        error = dlerror( );

+        printf( "ERROR\tCould not close library2: %s\n", error ? error : "" );

+        RETURN_ERROR;

+    }

+    else

+        printf( "SUCCESS\tClosed library2.\n" );

+

     library = dlopen( "testdll.dll", RTLD_LOCAL );

     if( !library )

     {