Do not modify the compr buffer pointer.

The compr pointer points to the allocated memory. We must not modify
it value.
If we advance the pointer by two bytes each time we compress an answer
we will end to write in some random memory and segfault.

Now, we use a std::vector to correctly handle allocation
(and deallocation!) of the memory.

src/server/kiwix-serve.cpp

@@ -49,6 +49,7 @@ extern "C" {
 #include <getopt.h>
 #include <iostream>
 #include <string>
+#include <vector>
 #include <map>
 #include <fstream>
 #include <iostream>
@@ -142,14 +143,13 @@ bool isVerbose() {
 
 /* For compression */
 #define COMPRESSOR_BUFFER_SIZE 10000000
-static Bytef *compr = (Bytef *)malloc(COMPRESSOR_BUFFER_SIZE);
-static uLongf comprLen;
-
 
 static
 bool compress_content(string &content,
                       const string &mimeType)
 {
+  static std::vector<Bytef> compr_buffer;
+
   /* Compute the lengh */
   unsigned int contentLength = content.size();
 
@@ -164,8 +164,9 @@ bool compress_content(string &content,
   /* Compress the content if necessary */
   if (deflated) {
     pthread_mutex_lock(&compressorLock);
-    comprLen = COMPRESSOR_BUFFER_SIZE;
-    compress(compr, &comprLen, (const Bytef*)(content.data()), contentLength);
+    compr_buffer.reserve(COMPRESSOR_BUFFER_SIZE);
+    uLongf comprLen = COMPRESSOR_BUFFER_SIZE;
+    compress(&compr_buffer[0], &comprLen, (const Bytef*)(content.data()), contentLength);
 
     if (comprLen > 2 && comprLen < (contentLength+2)) {
 
@@ -174,11 +175,8 @@ bool compress_content(string &content,
 	 We need to chunk them off (move the content 2bytes)
 	 It has no incidence on other browsers
 	 See http://www.subbu.org/blog/2008/03/ie7-deflate-or-not and comments */
-      compr += 2;
-      comprLen -= 2;
 
-      content = string((char *)compr, comprLen);
-      contentLength = comprLen;
+      content = string((char *)&compr_buffer[2], comprLen-2);
     } else {
       deflated = false;
     }