title: Need to know which gcc switches I miss to compile a C script
body: <p>I try to validate a <a href="/questions/tagged/x509" class="post-tag" title="show questions tagged &#39;x509&#39;" rel="tag">x509</a> signature from a <a href="/questions/tagged/c" class="post-tag" title="show questions tagged &#39;c&#39;" rel="tag">c</a> script, but I can't figure out what I miss to compile it successfully.</p>
  
  <p>I use Ubuntu 13.10, xmlsec1 1.2.18 (openssl), libxml2 2.9.1.</p>
  
  <p>What I tried : </p>
  
  <pre><code>gcc -I/usr/include/xmlsec1 -I/usr/include/libxml2 -o xmlsec-verify-with-X509 xmlsec-verify-with-X509.c 
  </code></pre>
  
  <p>But I get :</p>
  
  <pre><code>In file included from xmlsec-verify-with-X509.c:39:0:
  /usr/include/xmlsec1/xmlsec/crypto.h:59:2: error: #error No crypto library defined
   #error No crypto library defined
    ^
  </code></pre>
  
  <p>The crypto.h file until line 59 :</p>
  
  <pre><code>#ifdef XMLSEC_CRYPTO_DYNAMIC_LOADING
  #include &lt;xmlsec/app.h&gt;
  #else /* XMLSEC_CRYPTO_DYNAMIC_LOADING */
  #ifdef XMLSEC_CRYPTO_OPENSSL
  #include &lt;xmlsec/openssl/app.h&gt;
  #include &lt;xmlsec/openssl/crypto.h&gt;
  #include &lt;xmlsec/openssl/x509.h&gt;
  #include &lt;xmlsec/openssl/symbols.h&gt;
  #else /* XMLSEC_CRYPTO_OPENSSL */
  #ifdef XMLSEC_CRYPTO_MSCRYPTO
  #include &lt;xmlsec/mscrypto/app.h&gt;
  #include &lt;xmlsec/mscrypto/crypto.h&gt;
  #include &lt;xmlsec/mscrypto/x509.h&gt;
  #include &lt;xmlsec/mscrypto/symbols.h&gt;
  #else /* XMLSEC_CRYPTO_MSCRYPTO */
  #ifdef XMLSEC_CRYPTO_NSS
  #include &lt;xmlsec/nss/app.h&gt;
  #include &lt;xmlsec/nss/crypto.h&gt;
  #include &lt;xmlsec/openssl/x509.h&gt;
  #include &lt;xmlsec/nss/symbols.h&gt;
  #else /* XMLSEC_CRYPTO_NSS */
  #ifdef XMLSEC_CRYPTO_GNUTLS
  #include &lt;xmlsec/gnutls/app.h&gt;
  #include &lt;xmlsec/gnutls/crypto.h&gt;
  #include &lt;xmlsec/gnutls/symbols.h&gt;
  #else /* XMLSEC_CRYPTO_GNUTLS */
  #ifdef XMLSEC_CRYPTO_GCRYPT
  #include &lt;xmlsec/gcrypt/app.h&gt;
  #include &lt;xmlsec/gcrypt/crypto.h&gt;
  #include &lt;xmlsec/gcrypt/symbols.h&gt;
  #else /* XMLSEC_CRYPTO_GCRYPT */
  #error No crypto library defined
  </code></pre>
  
  <p>The script comes from <a href="http://www.aleksey.com/xmlsec/api/xmlsec-verify-with-x509.html" rel="nofollow">http://www.aleksey.com/xmlsec/api/xmlsec-verify-with-x509.html</a> :</p>
  
  <pre><code>#include &lt;stdlib.h&gt;
  #include &lt;string.h&gt;
  #include &lt;assert.h&gt;
  
  #include &lt;libxml/tree.h&gt;
  #include &lt;libxml/xmlmemory.h&gt;
  #include &lt;libxml/parser.h&gt;
  
  #ifndef XMLSEC_NO_XSLT
  #include &lt;libxslt/xslt.h&gt;
  #include &lt;libxslt/security.h&gt;
  #endif /* XMLSEC_NO_XSLT */
  
  #include &lt;xmlsec/xmlsec.h&gt;
  #include &lt;xmlsec/xmltree.h&gt;
  #include &lt;xmlsec/xmldsig.h&gt;
  #include &lt;xmlsec/crypto.h&gt;
  
  xmlSecKeysMngrPtr load_trusted_certs(char** files, int files_size);
  int verify_file(xmlSecKeysMngrPtr mngr, const char* xml_file);
  
  int 
  main(int argc, char **argv) {
  #ifndef XMLSEC_NO_XSLT
      xsltSecurityPrefsPtr xsltSecPrefs = NULL;
  #endif /* XMLSEC_NO_XSLT */
      xmlSecKeysMngrPtr mngr;
  
      assert(argv);
  
      if(argc &lt; 3) {
          fprintf(stderr, "Error: wrong number of arguments.\n");
          fprintf(stderr, "Usage: %s &lt;xml-file&gt; &lt;cert-file1&gt; [&lt;cert-file2&gt; [...]]\n", argv[0]);
          return(1);
      }
  
      /* Init libxml and libxslt libraries */
      xmlInitParser();
      LIBXML_TEST_VERSION
      xmlLoadExtDtdDefaultValue = XML_DETECT_IDS | XML_COMPLETE_ATTRS;
      xmlSubstituteEntitiesDefault(1);
  #ifndef XMLSEC_NO_XSLT
      xmlIndentTreeOutput = 1; 
  #endif /* XMLSEC_NO_XSLT */
  
      /* Init libxslt */
  #ifndef XMLSEC_NO_XSLT
      /* disable everything */
      xsltSecPrefs = xsltNewSecurityPrefs(); 
      xsltSetSecurityPrefs(xsltSecPrefs,  XSLT_SECPREF_READ_FILE,        xsltSecurityForbid);
      xsltSetSecurityPrefs(xsltSecPrefs,  XSLT_SECPREF_WRITE_FILE,       xsltSecurityForbid);
      xsltSetSecurityPrefs(xsltSecPrefs,  XSLT_SECPREF_CREATE_DIRECTORY, xsltSecurityForbid);
      xsltSetSecurityPrefs(xsltSecPrefs,  XSLT_SECPREF_READ_NETWORK,     xsltSecurityForbid);
      xsltSetSecurityPrefs(xsltSecPrefs,  XSLT_SECPREF_WRITE_NETWORK,    xsltSecurityForbid);
      xsltSetDefaultSecurityPrefs(xsltSecPrefs); 
  #endif /* XMLSEC_NO_XSLT */
  
      /* Init xmlsec library */
      if(xmlSecInit() &lt; 0) {
          fprintf(stderr, "Error: xmlsec initialization failed.\n");
          return(-1);
      }
  
      /* Check loaded library version */
      if(xmlSecCheckVersion() != 1) {
          fprintf(stderr, "Error: loaded xmlsec library version is not compatible.\n");
          return(-1);
      }
  
      /* Load default crypto engine if we are supporting dynamic
       * loading for xmlsec-crypto libraries. Use the crypto library
       * name ("openssl", "nss", etc.) to load corresponding 
       * xmlsec-crypto library.
       */
  #ifdef XMLSEC_CRYPTO_DYNAMIC_LOADING
      if(xmlSecCryptoDLLoadLibrary(BAD_CAST XMLSEC_CRYPTO) &lt; 0) {
          fprintf(stderr, "Error: unable to load default xmlsec-crypto library. Make sure\n"
                          "that you have it installed and check shared libraries path\n"
                          "(LD_LIBRARY_PATH) envornment variable.\n");
          return(-1);     
      }
  #endif /* XMLSEC_CRYPTO_DYNAMIC_LOADING */
  
      /* Init crypto library */
      if(xmlSecCryptoAppInit(NULL) &lt; 0) {
          fprintf(stderr, "Error: crypto initialization failed.\n");
          return(-1);
      }
  
      /* Init xmlsec-crypto library */
      if(xmlSecCryptoInit() &lt; 0) {
          fprintf(stderr, "Error: xmlsec-crypto initialization failed.\n");
          return(-1);
      }
  
      /* create keys manager and load trusted certificates */
      mngr = load_trusted_certs(&amp;(argv[2]), argc - 2);
      if(mngr == NULL) {
          return(-1);
      }
  
      /* verify file */
      if(verify_file(mngr, argv[1]) &lt; 0) {
          xmlSecKeysMngrDestroy(mngr);    
          return(-1);
      }    
  
      /* destroy keys manager */
      xmlSecKeysMngrDestroy(mngr);
  
      /* Shutdown xmlsec-crypto library */
      xmlSecCryptoShutdown();
  
      /* Shutdown crypto library */
      xmlSecCryptoAppShutdown();
  
      /* Shutdown xmlsec library */
      xmlSecShutdown();
  
      /* Shutdown libxslt/libxml */
  #ifndef XMLSEC_NO_XSLT
      xsltFreeSecurityPrefs(xsltSecPrefs);
      xsltCleanupGlobals();            
  #endif /* XMLSEC_NO_XSLT */
      xmlCleanupParser();
  
      return(0);
  }
  
  /**
   * load_trusted_certs:
   * @files:              the list of filenames.
   * @files_size:         the number of filenames in #files.
   *
   * Creates simple keys manager and load trusted certificates from PEM #files.
   * The caller is responsible for destroing returned keys manager using
   * @xmlSecKeysMngrDestroy.
   *
   * Returns the pointer to newly created keys manager or NULL if an error
   * occurs.
   */
  xmlSecKeysMngrPtr 
  load_trusted_certs(char** files, int files_size) {
      xmlSecKeysMngrPtr mngr;
      int i;
  
      assert(files);
      assert(files_size &gt; 0);
  
      /* create and initialize keys manager, we use a simple list based
       * keys manager, implement your own xmlSecKeysStore klass if you need
       * something more sophisticated 
       */
      mngr = xmlSecKeysMngrCreate();
      if(mngr == NULL) {
          fprintf(stderr, "Error: failed to create keys manager.\n");
          return(NULL);
      }
      if(xmlSecCryptoAppDefaultKeysMngrInit(mngr) &lt; 0) {
          fprintf(stderr, "Error: failed to initialize keys manager.\n");
          xmlSecKeysMngrDestroy(mngr);
          return(NULL);
      }    
  
      for(i = 0; i &lt; files_size; ++i) {
          assert(files[i]);
  
          /* load trusted cert */
          if(xmlSecCryptoAppKeysMngrCertLoad(mngr, files[i], xmlSecKeyDataFormatPem, xmlSecKeyDataTypeTrusted) &lt; 0) {
              fprintf(stderr,"Error: failed to load pem certificate from \"%s\"\n", files[i]);
              xmlSecKeysMngrDestroy(mngr);
              return(NULL);
          }
      }
  
      return(mngr);
  }
  
  /** 
   * verify_file:
   * @mngr:               the pointer to keys manager.
   * @xml_file:           the signed XML file name.
   *
   * Verifies XML signature in #xml_file.
   *
   * Returns 0 on success or a negative value if an error occurs.
   */
  int 
  verify_file(xmlSecKeysMngrPtr mngr, const char* xml_file) {
      xmlDocPtr doc = NULL;
      xmlNodePtr node = NULL;
      xmlSecDSigCtxPtr dsigCtx = NULL;
      int res = -1;
  
      assert(mngr);
      assert(xml_file);
  
      /* load file */
      doc = xmlParseFile(xml_file);
      if ((doc == NULL) || (xmlDocGetRootElement(doc) == NULL)){
          fprintf(stderr, "Error: unable to parse file \"%s\"\n", xml_file);
          goto done;      
      }
  
      /* find start node */
      node = xmlSecFindNode(xmlDocGetRootElement(doc), xmlSecNodeSignature, xmlSecDSigNs);
      if(node == NULL) {
          fprintf(stderr, "Error: start node not found in \"%s\"\n", xml_file);
          goto done;      
      }
  
      /* create signature context */
      dsigCtx = xmlSecDSigCtxCreate(mngr);
      if(dsigCtx == NULL) {
          fprintf(stderr,"Error: failed to create signature context\n");
          goto done;
      }
  
      /* Verify signature */
      if(xmlSecDSigCtxVerify(dsigCtx, node) &lt; 0) {
          fprintf(stderr,"Error: signature verify\n");
          goto done;
      }
  
      /* print verification result to stdout */
      if(dsigCtx-&gt;status == xmlSecDSigStatusSucceeded) {
          fprintf(stdout, "Signature is OK\n");
      } else {
          fprintf(stdout, "Signature is INVALID\n");
      }    
  
      /* success */
      res = 0;
  
  done:    
      /* cleanup */
      if(dsigCtx != NULL) {
          xmlSecDSigCtxDestroy(dsigCtx);
      }
  
      if(doc != NULL) {
          xmlFreeDoc(doc); 
      }
      return(res);
  }
  </code></pre>
  
  <p><strong>Edit1</strong> :</p>
  
  <p>If I try with <code>-DXMLSEC_CRYPTO_OPENSSL</code></p>
  
  <pre><code>$ gcc -DXMLSEC_CRYPTO_OPENSSL -I/usr/include/xmlsec1 -I/usr/include/libxml2 -o xmlsec-verify-with-X509 xmlsec-verify-with-X509.c 
  /tmp/ccBwmeSC.o: In function `main':
  xmlsec-verify-with-X509.c:(.text+0x86): undefined reference to `xmlInitParser'
  xmlsec-verify-with-X509.c:(.text+0x90): undefined reference to `xmlCheckVersion'
  xmlsec-verify-with-X509.c:(.text+0x95): undefined reference to `__xmlLoadExtDtdDefaultValue'
  xmlsec-verify-with-X509.c:(.text+0xa5): undefined reference to `xmlSubstituteEntitiesDefault'
  xmlsec-verify-with-X509.c:(.text+0xaa): undefined reference to `__xmlIndentTreeOutput'
  xmlsec-verify-with-X509.c:(.text+0xb5): undefined reference to `xsltNewSecurityPrefs'
  xmlsec-verify-with-X509.c:(.text+0xc2): undefined reference to `xsltSecurityForbid'
  xmlsec-verify-with-X509.c:(.text+0xcf): undefined reference to `xsltSetSecurityPrefs'
  xmlsec-verify-with-X509.c:(.text+0xd8): undefined reference to `xsltSecurityForbid'
  xmlsec-verify-with-X509.c:(.text+0xe5): undefined reference to `xsltSetSecurityPrefs'
  xmlsec-verify-with-X509.c:(.text+0xee): undefined reference to `xsltSecurityForbid'
  xmlsec-verify-with-X509.c:(.text+0xfb): undefined reference to `xsltSetSecurityPrefs'
  xmlsec-verify-with-X509.c:(.text+0x104): undefined reference to `xsltSecurityForbid'
  xmlsec-verify-with-X509.c:(.text+0x111): undefined reference to `xsltSetSecurityPrefs'
  xmlsec-verify-with-X509.c:(.text+0x11a): undefined reference to `xsltSecurityForbid'
  xmlsec-verify-with-X509.c:(.text+0x127): undefined reference to `xsltSetSecurityPrefs'
  xmlsec-verify-with-X509.c:(.text+0x133): undefined reference to `xsltSetDefaultSecurityPrefs'
  xmlsec-verify-with-X509.c:(.text+0x138): undefined reference to `xmlSecInit'
  xmlsec-verify-with-X509.c:(.text+0x17d): undefined reference to `xmlSecCheckVersionExt'
  xmlsec-verify-with-X509.c:(.text+0x1b4): undefined reference to `xmlSecOpenSSLAppInit'
  xmlsec-verify-with-X509.c:(.text+0x1e5): undefined reference to `xmlSecOpenSSLInit'
  xmlsec-verify-with-X509.c:(.text+0x265): undefined reference to `xmlSecKeysMngrDestroy'
  xmlsec-verify-with-X509.c:(.text+0x278): undefined reference to `xmlSecKeysMngrDestroy'
  xmlsec-verify-with-X509.c:(.text+0x27d): undefined reference to `xmlSecOpenSSLShutdown'
  xmlsec-verify-with-X509.c:(.text+0x282): undefined reference to `xmlSecOpenSSLAppShutdown'
  xmlsec-verify-with-X509.c:(.text+0x287): undefined reference to `xmlSecShutdown'
  xmlsec-verify-with-X509.c:(.text+0x293): undefined reference to `xsltFreeSecurityPrefs'
  xmlsec-verify-with-X509.c:(.text+0x298): undefined reference to `xsltCleanupGlobals'
  xmlsec-verify-with-X509.c:(.text+0x29d): undefined reference to `xmlCleanupParser'
  /tmp/ccBwmeSC.o: In function `load_trusted_certs':
  xmlsec-verify-with-X509.c:(.text+0x2f7): undefined reference to `xmlSecKeysMngrCreate'
  xmlsec-verify-with-X509.c:(.text+0x336): undefined reference to `xmlSecOpenSSLAppDefaultKeysMngrInit'
  xmlsec-verify-with-X509.c:(.text+0x364): undefined reference to `xmlSecKeysMngrDestroy'
  xmlsec-verify-with-X509.c:(.text+0x3dc): undefined reference to `xmlSecOpenSSLAppKeysMngrCertLoad'
  xmlsec-verify-with-X509.c:(.text+0x41c): undefined reference to `xmlSecKeysMngrDestroy'
  /tmp/ccBwmeSC.o: In function `verify_file':
  xmlsec-verify-with-X509.c:(.text+0x4b4): undefined reference to `xmlParseFile'
  xmlsec-verify-with-X509.c:(.text+0x4cb): undefined reference to `xmlDocGetRootElement'
  xmlsec-verify-with-X509.c:(.text+0x4fe): undefined reference to `xmlDocGetRootElement'
  xmlsec-verify-with-X509.c:(.text+0x503): undefined reference to `xmlSecDSigNs'
  xmlsec-verify-with-X509.c:(.text+0x508): undefined reference to `xmlSecNodeSignature'
  xmlsec-verify-with-X509.c:(.text+0x510): undefined reference to `xmlSecFindNode'
  xmlsec-verify-with-X509.c:(.text+0x549): undefined reference to `xmlSecDSigCtxCreate'
  xmlsec-verify-with-X509.c:(.text+0x58a): undefined reference to `xmlSecDSigCtxVerify'
  xmlsec-verify-with-X509.c:(.text+0x615): undefined reference to `xmlSecDSigCtxDestroy'
  xmlsec-verify-with-X509.c:(.text+0x628): undefined reference to `xmlFreeDoc'
  collect2: error: ld returned 1 exit status
  </code></pre>
  
  <p>With <code>-DXMLSEC_CRYPTO_DYNAMIC_LOADING</code></p>
  
  <pre><code>$ gcc -DXMLSEC_CRYPTO_DYNAMIC_LOADING  -I/usr/include/xmlsec1 -I/usr/include/libxml2 -o xmlsec-verify-with-X509 xmlsec-verify-with-X509.c 
  xmlsec-verify-with-X509.c: In function 'main':
  xmlsec-verify-with-X509.c:76:43: error: 'XMLSEC_CRYPTO' undeclared (first use in this function)
       if(xmlSecCryptoDLLoadLibrary(BAD_CAST XMLSEC_CRYPTO) &lt; 0) {
                                             ^
  xmlsec-verify-with-X509.c:76:43: note: each undeclared identifier is reported only once for each function it appears in
  </code></pre>