test536: do not fail with threaded DNS resolver

Also tweaked comments in certain examples using curl_multi_fdset().

6 files changed, 30 insertions, 18 deletions

diff --git a/docs/examples/fopen.c b/docs/examples/fopen.c
index e3814e6ab..35e24b11f 100644
--- a/docs/examples/fopen.c
+++ b/docs/examples/fopen.c
@@ -131,7 +131,6 @@ fill_buffer(URL_FILE *file,int want,int waittime)
     fd_set fdread;
     fd_set fdwrite;
     fd_set fdexcep;
-    int maxfd;
     struct timeval timeout;
     int rc;
 
@@ -144,6 +143,7 @@ fill_buffer(URL_FILE *file,int want,int waittime)
     /* attempt to fill buffer */
     do
     {
+        int maxfd = -1;
         FD_ZERO(&fdread);
         FD_ZERO(&fdwrite);
         FD_ZERO(&fdexcep);
@@ -156,8 +156,10 @@ fill_buffer(URL_FILE *file,int want,int waittime)
         curl_multi_fdset(multi_handle, &fdread, &fdwrite, &fdexcep, &maxfd);
 
         /* In a real-world program you OF COURSE check the return code of the
-           function calls, *and* you make sure that maxfd is bigger than -1
-           so that the call to select() below makes sense! */
+           function calls.  On success, the value of maxfd is guaranteed to be
+           greater or equal than -1.  We call select(maxfd + 1, ...), specially
+           in case of (maxfd == -1), we call select(0, ...), which is basically
+           equal to sleep. */
 
         rc = select(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout);
 
diff --git a/docs/examples/multi-app.c b/docs/examples/multi-app.c
index a86dd0efd..38b50cd0d 100644
--- a/docs/examples/multi-app.c
+++ b/docs/examples/multi-app.c
@@ -66,7 +66,7 @@ int main(int argc, char **argv)
     fd_set fdread;
     fd_set fdwrite;
     fd_set fdexcep;
-    int maxfd;
+    int maxfd = -1;
 
     FD_ZERO(&fdread);
     FD_ZERO(&fdwrite);
@@ -80,8 +80,10 @@ int main(int argc, char **argv)
     curl_multi_fdset(multi_handle, &fdread, &fdwrite, &fdexcep, &maxfd);
 
     /* In a real-world program you OF COURSE check the return code of the
-       function calls, *and* you make sure that maxfd is bigger than -1 so
-       that the call to select() below makes sense! */
+       function calls.  On success, the value of maxfd is guaranteed to be
+       greater or equal than -1.  We call select(maxfd + 1, ...), specially in
+       case of (maxfd == -1), we call select(0, ...), which is basically equal
+       to sleep. */
 
     rc = select(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout);
 
diff --git a/docs/examples/multi-debugcallback.c b/docs/examples/multi-debugcallback.c
index b10b47cd1..8e964c67b 100644
--- a/docs/examples/multi-debugcallback.c
+++ b/docs/examples/multi-debugcallback.c
@@ -140,7 +140,7 @@ int main(int argc, char **argv)
     fd_set fdread;
     fd_set fdwrite;
     fd_set fdexcep;
-    int maxfd;
+    int maxfd = -1;
 
     FD_ZERO(&fdread);
     FD_ZERO(&fdwrite);
@@ -154,8 +154,10 @@ int main(int argc, char **argv)
     curl_multi_fdset(multi_handle, &fdread, &fdwrite, &fdexcep, &maxfd);
 
     /* In a real-world program you OF COURSE check the return code of the
-       function calls, *and* you make sure that maxfd is bigger than -1
-       so that the call to select() below makes sense! */
+       function calls.  On success, the value of maxfd is guaranteed to be
+       greater or equal than -1.  We call select(maxfd + 1, ...), specially in
+       case of (maxfd == -1), we call select(0, ...), which is basically equal
+       to sleep. */
 
     rc = select(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout);
 
diff --git a/docs/examples/multi-double.c b/docs/examples/multi-double.c
index ef3bf92fc..bc5b446ea 100644
--- a/docs/examples/multi-double.c
+++ b/docs/examples/multi-double.c
@@ -57,7 +57,7 @@ int main(int argc, char **argv)
     fd_set fdread;
     fd_set fdwrite;
     fd_set fdexcep;
-    int maxfd;
+    int maxfd = -1;
 
     FD_ZERO(&fdread);
     FD_ZERO(&fdwrite);
@@ -71,8 +71,10 @@ int main(int argc, char **argv)
     curl_multi_fdset(multi_handle, &fdread, &fdwrite, &fdexcep, &maxfd);
 
     /* In a real-world program you OF COURSE check the return code of the
-       function calls, *and* you make sure that maxfd is bigger than -1 so
-       that the call to select() below makes sense! */
+       function calls.  On success, the value of maxfd is guaranteed to be
+       greater or equal than -1.  We call select(maxfd + 1, ...), specially in
+       case of (maxfd == -1), we call select(0, ...), which is basically equal
+       to sleep. */
 
     rc = select(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout);
 
diff --git a/docs/examples/multi-post.c b/docs/examples/multi-post.c
index 229e84306..0d3f78e5e 100644
--- a/docs/examples/multi-post.c
+++ b/docs/examples/multi-post.c
@@ -77,7 +77,7 @@ int main(int argc, char *argv[])
       fd_set fdread;
       fd_set fdwrite;
       fd_set fdexcep;
-      int maxfd;
+      int maxfd = -1;
 
       FD_ZERO(&fdread);
       FD_ZERO(&fdwrite);
@@ -91,8 +91,10 @@ int main(int argc, char *argv[])
       curl_multi_fdset(multi_handle, &fdread, &fdwrite, &fdexcep, &maxfd);
 
       /* In a real-world program you OF COURSE check the return code of the
-         function calls, *and* you make sure that maxfd is bigger than -1
-         so that the call to select() below makes sense! */
+         function calls.  On success, the value of maxfd is guaranteed to be
+         greater or equal than -1.  We call select(maxfd + 1, ...), specially in
+         case of (maxfd == -1), we call select(0, ...), which is basically equal
+         to sleep. */
 
       rc = select(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout);
 
diff --git a/docs/examples/multi-single.c b/docs/examples/multi-single.c
index 3e236f326..cba4f32cc 100644
--- a/docs/examples/multi-single.c
+++ b/docs/examples/multi-single.c
@@ -51,7 +51,7 @@ int main(int argc, char **argv)
     fd_set fdread;
     fd_set fdwrite;
     fd_set fdexcep;
-    int maxfd;
+    int maxfd = -1;
 
     FD_ZERO(&fdread);
     FD_ZERO(&fdwrite);
@@ -65,8 +65,10 @@ int main(int argc, char **argv)
     curl_multi_fdset(multi_handle, &fdread, &fdwrite, &fdexcep, &maxfd);
 
     /* In a real-world program you OF COURSE check the return code of the
-       function calls, *and* you make sure that maxfd is bigger than -1 so
-       that the call to select() below makes sense! */
+       function calls.  On success, the value of maxfd is guaranteed to be
+       greater or equal than -1.  We call select(maxfd + 1, ...), specially in
+       case of (maxfd == -1), we call select(0, ...), which is basically equal
+       to sleep. */
 
     rc = select(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout);