examples: Fix memory leaks from realloc errors

Make sure to not overwrite the reallocated pointer in realloc() calls
to avoid a memleak on memory errors.

docs/examples/crawler.c

@@ -52,7 +52,13 @@ size_t grow_buffer(void *contents, size_t sz, size_t nmemb, void *ctx)
 {
   size_t realsize = sz * nmemb;
   memory *mem = (memory*) ctx;
-  mem->buf = realloc(mem->buf, mem->size + realsize);
+  char *ptr = realloc(mem->buf, mem->size + realsize);
+  if(!ptr) {
+    /* out of memory */
+    printf("not enough memory (realloc returned NULL)\n");
+    return 0;
+  }
+  mem->buf = ptr;
   memcpy(&(mem->buf[mem->size]), contents, realsize);
   mem->size += realsize;
   return realsize;

docs/examples/curlx.c

@@ -515,12 +515,20 @@ int main(int argc, char **argv)
   curl_easy_setopt(p.curl, CURLOPT_SSL_CTX_DATA, &p);
 
   {
+    char *ptr;
     int lu; int i = 0;
     while((lu = BIO_read(in, &binaryptr[i], tabLength-i)) >0) {
       i += lu;
       if(i == tabLength) {
         tabLength += 100;
-        binaryptr = realloc(binaryptr, tabLength); /* should be more careful */
+        ptr = realloc(binaryptr, tabLength); /* should be more careful */
+        if(!ptr) {
+          /* out of memory */
+          BIO_printf(p.errorbio, "out of memory (realloc returned NULL)\n");
+          goto fail;
+        }
+        binaryptr = ptr;
+        ptr = NULL;
       }
     }
     tabLength = i;
@@ -551,7 +559,7 @@ int main(int argc, char **argv)
   /*** code d'erreur si accept mime ***, egalement code return HTTP != 200 ***/
 
 /* free the header list*/
-
+fail:
   curl_slist_free_all(headers);
 
   /* always cleanup */

docs/examples/getinmemory.c

@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2018, 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
@@ -42,13 +42,14 @@ WriteMemoryCallback(void *contents, size_t size, size_t nmemb, void *userp)
   size_t realsize = size * nmemb;
   struct MemoryStruct *mem = (struct MemoryStruct *)userp;
 
-  mem->memory = realloc(mem->memory, mem->size + realsize + 1);
-  if(mem->memory == NULL) {
+  char *ptr = realloc(mem->memory, mem->size + realsize + 1);
+  if(ptr == NULL) {
     /* out of memory! */
     printf("not enough memory (realloc returned NULL)\n");
     return 0;
   }
 
+  mem->memory = ptr;
   memcpy(&(mem->memory[mem->size]), contents, realsize);
   mem->size += realsize;
   mem->memory[mem->size] = 0;

docs/examples/postinmemory.c

@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2018, 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
@@ -39,13 +39,14 @@ WriteMemoryCallback(void *contents, size_t size, size_t nmemb, void *userp)
   size_t realsize = size * nmemb;
   struct MemoryStruct *mem = (struct MemoryStruct *)userp;
 
-  mem->memory = realloc(mem->memory, mem->size + realsize + 1);
-  if(mem->memory == NULL) {
+  char *ptr = realloc(mem->memory, mem->size + realsize + 1);
+  if(!ptr) {
     /* out of memory! */
     printf("not enough memory (realloc returned NULL)\n");
     return 0;
   }
 
+  mem->memory = ptr;
   memcpy(&(mem->memory[mem->size]), contents, realsize);
   mem->size += realsize;
   mem->memory[mem->size] = 0;

docs/examples/xmlstream.c

@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2018, 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
@@ -69,14 +69,15 @@ static void characterDataHandler(void *userData, const XML_Char *s, int len)
   struct ParserStruct *state = (struct ParserStruct *) userData;
   struct MemoryStruct *mem = &state->characters;
 
-  mem->memory = realloc(mem->memory, mem->size + len + 1);
-  if(mem->memory == NULL) {
+  char *ptr = realloc(mem->memory, mem->size + len + 1);
+  if(!ptr) {
     /* Out of memory. */
     fprintf(stderr, "Not enough memory (realloc returned NULL).\n");
     state->ok = 0;
     return;
   }
 
+  mem->memory = ptr;
   memcpy(&(mem->memory[mem->size]), s, len);
   mem->size += len;
   mem->memory[mem->size] = 0;