[gnutls-devel] GnuTLS | tpm2: dynamically load tss2 libraries as needed (!1544)

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Thu Feb 24 09:42:07 CET 2022

Richard W_M_ Jones commented:

There's actually a trick using `typeof` which avoids redefining each variable type (and it's more type safe).  However I'm not sure if it requires a GCC extension or not.  See example:

#include <stdio.h>                                                              
#include <stdlib.h>                                                             
#include <assert.h>                                                             
#include <tss2/tss2_esys.h>                                                     
#include <dlfcn.h>                                                              
typeof(Esys_Initialize) (*my_Esys_Initialize);                                  
typeof(Esys_Finalize) (*my_Esys_Finalize);                                      
main ()                                                                         
  void *dl = dlopen ("libtss2-esys.so.0", RTLD_NOW);                            
  assert (dl);                                                                  
  my_Esys_Initialize = dlsym (dl, "Esys_Initialize");                           
  assert (my_Esys_Initialize);                                                  
  my_Esys_Finalize = dlsym (dl, "Esys_Finalize");                               
  assert (my_Esys_Finalize);                                                    
  ESYS_CONTEXT *ctx;                                                            
  if (my_Esys_Initialize (&ctx, NULL, NULL)) {                                  
    fprintf (stderr, "Esys_Initialize failed\n");                               
    exit (1);                                                                   
  fprintf (stderr, "ctx = %p\n", ctx);                                          
  my_Esys_Finalize (&ctx);                                                      
  exit (0);                                                                     

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