typecheck-gcc.h: check CURLINFO_CERTINFO

... and update the certinfo.c example accordingly.

Fixes https://github.com/curl/curl/issues/846

docs/KNOWN_BUGS

@@ -49,7 +49,6 @@ problems may have been fixed or changed somewhat since this was written!
  5.7 Visual Studio project gaps
  5.8 configure finding libs in wrong directory
  5.9 Utilize Requires.private directives in libcurl.pc
- 5.10 Fix the gcc typechecks
 
  6. Authentication
  6.1 NTLM authentication and unicode
@@ -364,14 +363,6 @@ problems may have been fixed or changed somewhat since this was written!
 
  https://github.com/curl/curl/issues/864
 
-5.10 Fix the gcc typechecks
-
- Issue #846 identifies a problem with the gcc-typechecks and how the types are
- documented and checked for CURLINFO_CERTINFO but our attempts to fix the
- issue were futile and needs more attention.
-
- https://github.com/curl/curl/issues/846
-
 6. Authentication
 
 6.1 NTLM authentication and unicode

docs/examples/certinfo.c

@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -56,24 +56,19 @@ int main(void)
     res = curl_easy_perform(curl);
 
     if(!res) {
-      union {
-        struct curl_slist    *to_info;
-        struct curl_certinfo *to_certinfo;
-      } ptr;
+      struct curl_certinfo *certinfo;
 
-      ptr.to_info = NULL;
+      res = curl_easy_getinfo(curl, CURLINFO_CERTINFO, &certinfo);
 
-      res = curl_easy_getinfo(curl, CURLINFO_CERTINFO, &ptr.to_info);
-
-      if(!res && ptr.to_info) {
+      if(!res && certinfo) {
         int i;
 
-        printf("%d certs!\n", ptr.to_certinfo->num_of_certs);
+        printf("%d certs!\n", certinfo->num_of_certs);
 
-        for(i = 0; i < ptr.to_certinfo->num_of_certs; i++) {
+        for(i = 0; i < certinfo->num_of_certs; i++) {
           struct curl_slist *slist;
 
-          for(slist = ptr.to_certinfo->certinfo[i]; slist; slist = slist->next)
+          for(slist = certinfo->certinfo[i]; slist; slist = slist->next)
             printf("%s\n", slist->data);
 
         }

include/curl/typecheck-gcc.h

@@ -127,6 +127,9 @@ __extension__ ({                                                              \
     if(_curl_is_tlssessioninfo_info(_curl_info))                              \
       if(!_curl_is_arr((arg), struct curl_tlssessioninfo *))                  \
         _curl_easy_getinfo_err_curl_tlssesssioninfo();                        \
+    if(_curl_is_certinfo_info(_curl_info))                                    \
+      if(!_curl_is_arr((arg), struct curl_certinfo *))                        \
+        _curl_easy_getinfo_err_curl_certinfo();                               \
    if(_curl_is_socket_info(_curl_info))                                       \
       if(!_curl_is_arr((arg), curl_socket_t))                                 \
         _curl_easy_getinfo_err_curl_socket();                                 \
@@ -210,6 +213,9 @@ _CURL_WARNING(_curl_easy_getinfo_err_curl_slist,
 _CURL_WARNING(_curl_easy_getinfo_err_curl_tlssesssioninfo,
               "curl_easy_getinfo expects a pointer to "
               "'struct curl_tlssessioninfo *' for this info")
+_CURL_WARNING(_curl_easy_getinfo_err_curl_certinfo,
+              "curl_easy_getinfo expects a pointer to "
+              "'struct curl_certinfo *' for this info")
 _CURL_WARNING(_curl_easy_getinfo_err_curl_socket,
   "curl_easy_getinfo expects a pointer to curl_socket_t for this info")
 
@@ -380,6 +386,9 @@ _CURL_WARNING(_curl_easy_getinfo_err_curl_socket,
 #define _curl_is_tlssessioninfo_info(info)                              \
   (((info) == CURLINFO_TLS_SSL_PTR) || ((info) == CURLINFO_TLS_SESSION))
 
+/* true if info expects a pointer to struct curl_certinfo * argument */
+#define _curl_is_certinfo_info(info) ((info) == CURLINFO_CERTINFO)
+
 /* true if info expects a pointer to struct curl_socket_t argument */
 #define _curl_is_socket_info(info)                                            \
   (CURLINFO_SOCKET < (info))