1 files changed, 45 insertions, 16 deletions
diff --git a/lib/curl_gethostname.c b/lib/curl_gethostname.c
index 5a8c6494b..7f0bfed54 100644
--- a/lib/curl_gethostname.c
+++ b/lib/curl_gethostname.c
@@ -21,32 +21,61 @@
  ***************************************************************************/
 
 #include "setup.h"
+
+#ifdef HAVE_UNISTD_H
+#  include <unistd.h>
+#endif
+
 #include "curl_gethostname.h"
 
-#include <stdlib.h>
-#include <string.h>
-#include <unistd.h>
+/*
+ * Curl_gethostname() is a wrapper around gethostname() which allows
+ * overriding the host name that the function would normally return.
+ * This capability is used by the test suite to verify exact matching
+ * of NTLM authentication, which exercises libcurl's MD4 and DES code.
+ *
+ * For libcurl debug enabled builds host name overriding takes place
+ * when environment variable CURL_GETHOSTNAME is set, using the value
+ * held by the variable to override returned host name.
+ *
+ * For libcurl shared library release builds the test suite preloads
+ * another shared library named libhostname using the LD_PRELOAD
+ * mechanism which intercepts, and might override, the gethostname()
+ * function call. In this case a given platform must support the
+ * LD_PRELOAD mechanism and additionally have environment variable
+ * CURL_GETHOSTNAME set in order to override the returned host name.
+ *
+ * For libcurl static library release builds no overriding takes place.
+ */
 
-#define GETHOSTNAME_ENV_VAR "CURL_GETHOSTNAME"
+int Curl_gethostname(char *name, GETHOSTNAME_TYPE_ARG2 namelen) {
 
-int Curl_gethostname(char *name, size_t namelen) {
-#ifdef HAVE_GETHOSTNAME
+#ifndef HAVE_GETHOSTNAME
 
-#ifdef CURLDEBUG
-  /* we check the environment variable only in case of debug build */
-  const char *force_hostname = getenv(GETHOSTNAME_ENV_VAR);
+  /* Allow compilation and return failure when unavailable */
+  (void) name;
+  (void) namelen;
+  return -1;
+
+#else
+
+#ifdef DEBUGBUILD
+
+  /* Override host name when environment variable CURL_GETHOSTNAME is set */
+  const char *force_hostname = getenv("CURL_GETHOSTNAME");
   if(force_hostname) {
     strncpy(name, force_hostname, namelen);
+    name[namelen-1] = '\0';
     return 0;
   }
-#endif
-  /* no override requested */
+
+#endif /* DEBUGBUILD */
+
+  /* The call to system's gethostname() might get intercepted by the
+     libhostname library when libcurl is built as a non-debug shared
+     library when running the test suite. */
   return gethostname(name, namelen);
 
-#else
-  /* no gethostname() available on system, we should always fail */
-  (void) name;
-  (void) namelen;
-  return -1;
 #endif
+
 }