checksrc: reduce directory-specific exceptions

By making them defaults, then fixing and/or reshuffling remaining
exceptions as necessary.

- checksrc: ban by default: `snprintf`, `vsnprintf`, `sscanf`, `strtol`.
- examples: replace `strtol` with `atoi` to avoid a checksrc exception.
- tests/libtest: replace `strtol` with `atol`.
- tests/server: replace most `strtol` with `atol`.
- tests/server: replace most `strtoul` with `atol`/`atoi`.
- tests/server: drop no longer used `util_ultous`.
- fix typo in checksrc rules: `vsnprint` -> `vsnprintf`.
- update local exceptions.

Also:
- examples: ban curl printf functions. They're discouraged in user code.
- examples: replace curl printf with system printf.
  Add `snprintf` workaround for <VS2015.
- examples/synctime: fix `-Wfloat-equal`.
- examples/synctime: exclude for non-Windows and non-UWP Windows.
- examples/synctime: build by default.

Closes #18823

docs/examples/.checksrc

@@ -4,4 +4,14 @@ allowfunc fopen
 allowfunc gmtime
 allowfunc localtime
 allowfunc open
+allowfunc snprintf
 allowfunc socket
+allowfunc sscanf
+banfunc curl_maprintf
+banfunc curl_mfprintf
+banfunc curl_mprintf
+banfunc curl_msnprintf
+banfunc curl_mvaprintf
+banfunc curl_mvfprintf
+banfunc curl_mvprintf
+banfunc curl_mvsnprintf

docs/examples/Makefile.inc

@@ -132,6 +132,7 @@ check_PROGRAMS = \
   smtp-tls \
   smtp-vrfy \
   sslbackend \
+  synctime \
   unixsocket \
   url2file \
   urlapi \
@@ -155,7 +156,6 @@ COMPLICATED_EXAMPLES = \
   multithread.c \
   sessioninfo.c \
   smooth-gtk-thread.c \
-  synctime.c \
   threaded-ssl.c \
   usercertinmem.c \
   version-check.pl \

docs/examples/chkspeed.c

@@ -100,7 +100,7 @@ int main(int argc, char *argv[])
         case 'm':
         case 'M':
           if(argv[0][2] == '=') {
-            long m = strtol((*argv) + 3, NULL, 10);
+            int m = atoi((*argv) + 3);
             switch(m) {
             case 1:
               url = URL_1M;

docs/examples/cookie_interface.c

@@ -34,6 +34,10 @@
 #include <curl/curl.h>
 #include <curl/mprintf.h>
 
+#if defined(_MSC_VER) && (_MSC_VER < 1900)
+#define snprintf _snprintf
+#endif
+
 static int print_cookies(CURL *curl)
 {
   CURLcode res;
@@ -93,10 +97,10 @@ main(void)
     printf("-----------------------------------------------\n"
            "Setting a cookie \"PREF\" via cookie interface:\n");
     /* Netscape format cookie */
-    curl_msnprintf(nline, sizeof(nline), "%s\t%s\t%s\t%s\t%.0f\t%s\t%s",
-                   ".example.com", "TRUE", "/", "FALSE",
-                   difftime(time(NULL) + 31337, (time_t)0),
-                   "PREF", "hello example, i like you!");
+    snprintf(nline, sizeof(nline), "%s\t%s\t%s\t%s\t%.0f\t%s\t%s",
+             ".example.com", "TRUE", "/", "FALSE",
+             difftime(time(NULL) + 31337, (time_t)0),
+             "PREF", "hello example, I like you!");
     res = curl_easy_setopt(curl, CURLOPT_COOKIELIST, nline);
     if(res != CURLE_OK) {
       fprintf(stderr, "Curl curl_easy_setopt failed: %s\n",
@@ -109,7 +113,7 @@ main(void)
        modified, likely not what you intended. For more information refer to
        the CURLOPT_COOKIELIST documentation.
     */
-    curl_msnprintf(nline, sizeof(nline),
+    snprintf(nline, sizeof(nline),
       "Set-Cookie: OLD_PREF=3d141414bf4209321; "
       "expires=Sun, 17-Jan-2038 19:14:07 GMT; path=/; domain=.example.com");
     res = curl_easy_setopt(curl, CURLOPT_COOKIELIST, nline);

docs/examples/http2-download.c

@@ -38,6 +38,10 @@
 #include <curl/curl.h>
 #include <curl/mprintf.h>
 
+#if defined(_MSC_VER) && (_MSC_VER < 1900)
+#define snprintf _snprintf
+#endif
+
 #ifndef CURLPIPE_MULTIPLEX
 /* This little trick makes sure that we do not enable pipelining for libcurls
    old enough to not have this symbol. It is _not_ defined to zero in a recent
@@ -149,7 +153,7 @@ static int setup(struct transfer *t, int num)
 
   hnd = t->easy = curl_easy_init();
 
-  curl_msnprintf(filename, 128, "dl-%d", num);
+  snprintf(filename, sizeof(filename), "dl-%d", num);
 
   t->out = fopen(filename, "wb");
   if(!t->out) {

docs/examples/http2-serverpush.c

@@ -33,6 +33,10 @@
 #include <curl/curl.h>
 #include <curl/mprintf.h>
 
+#if defined(_MSC_VER) && (_MSC_VER < 1900)
+#define snprintf _snprintf
+#endif
+
 #ifndef CURLPIPE_MULTIPLEX
 #error "too old libcurl, cannot do HTTP/2 server push!"
 #endif
@@ -173,7 +177,7 @@ static int server_push_callback(CURL *parent,
 
   (void)parent;
 
-  curl_msnprintf(filename, 128, "push%u", count++);
+  snprintf(filename, sizeof(filename), "push%u", count++);
 
   /* here's a new stream, save it in a new file for each new push */
   out = fopen(filename, "wb");

docs/examples/http2-upload.c

@@ -40,6 +40,8 @@
 #ifndef _MSC_VER
 #include <sys/time.h>
 #include <unistd.h>
+#elif (_MSC_VER < 1900)
+#define snprintf _snprintf
 #endif
 
 #ifdef _WIN32
@@ -162,8 +164,8 @@ int my_trace(CURL *handle, curl_infotype type,
   }
   secs = epoch_offset + tv.tv_sec;
   now = localtime(&secs);  /* not thread safe but we do not care */
-  curl_msnprintf(timebuf, sizeof(timebuf), "%02d:%02d:%02d.%06ld",
-                 now->tm_hour, now->tm_min, now->tm_sec, (long)tv.tv_usec);
+  snprintf(timebuf, sizeof(timebuf), "%02d:%02d:%02d.%06ld",
+           now->tm_hour, now->tm_min, now->tm_sec, (long)tv.tv_usec);
 
   switch(type) {
   case CURLINFO_TEXT:
@@ -215,7 +217,7 @@ static int setup(struct input *i, int num, const char *upload)
   hnd = i->hnd = NULL;
 
   i->num = num;
-  curl_msnprintf(filename, 128, "dl-%d", num);
+  snprintf(filename, sizeof(filename), "dl-%d", num);
   out = fopen(filename, "wb");
   if(!out) {
     fprintf(stderr, "error: could not open file %s for writing: %s\n", upload,
@@ -223,7 +225,7 @@ static int setup(struct input *i, int num, const char *upload)
     return 1;
   }
 
-  curl_msnprintf(url, 256, "https://localhost:8443/upload-%d", num);
+  snprintf(url, sizeof(url), "https://localhost:8443/upload-%d", num);
 
   i->in = fopen(upload, "rb");
   if(!i->in) {

docs/examples/synctime.c

@@ -72,15 +72,32 @@
  */
 
 #include <stdio.h>
-#include <time.h>
-#include <curl/curl.h>
 
-#ifdef _WIN32
-#include <windows.h>
+#ifndef _WIN32
+int main(void) { printf("Platform not supported.\n"); return 1; }
 #else
-#error "This example requires Windows."
+
+#if (defined(_WIN32_WINNT) && (_WIN32_WINNT >= 0x0602)) || \
+   defined(WINAPI_FAMILY)
+#  include <winapifamily.h>
+#  if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP) &&  \
+     !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
+#    define CURL_WINDOWS_UWP
+#  endif
 #endif
 
+#ifdef CURL_WINDOWS_UWP
+int main(void) { printf("Platform not supported.\n"); return 1; }
+#else
+
+#include <windows.h>
+#include <time.h>
+
+#include <curl/curl.h>
+
+#if defined(_MSC_VER) && (_MSC_VER < 1900)
+#define snprintf _snprintf
+#endif
 
 #define MAX_STRING              256
 #define MAX_STRING1             MAX_STRING + 1
@@ -139,7 +156,7 @@ static size_t SyncTime_CURL_WriteHeader(void *ptr, size_t size, size_t nmemb,
       *TmpStr1 = 0;
       *TmpStr2 = 0;
       if(strlen((char *)(ptr)) > 50) /* Can prevent buffer overflow to
-                                         TmpStr1 & 2? */
+                                        TmpStr1 & 2? */
         AutoSyncTime = 0;
       else {
         int RetVal = sscanf((char *)(ptr), "Date: %25s %hu %s %hu %hu:%hu:%hu",
@@ -305,7 +322,7 @@ int main(int argc, char *argv[])
     tzonediffFloat = difftime(tt_local, tt_gmt);
     tzonediffWord  = (int)(tzonediffFloat/3600.0);
 
-    if((double)(tzonediffWord * 3600) == tzonediffFloat)
+    if(tzonediffWord == (int)(tzonediffFloat/3600.0))
       snprintf(tzoneBuf, sizeof(tzoneBuf), "%+03d'00'", tzonediffWord);
     else
       snprintf(tzoneBuf, sizeof(tzoneBuf), "%+03d'30'", tzonediffWord);
@@ -358,3 +375,5 @@ int main(int argc, char *argv[])
   }
   return RetValue;
 }
+#endif /* CURL_WINDOWS_UWP */
+#endif /* _WIN32 */