Fix bug #410274 - sys.prefix isn't always set.

If after calculating sys.path we do not have sys.prefix set, we loop over all path entries checking if one can point to our home directory.

diff --git a/PC/getpathp.c b/PC/getpathp.c
index f32c9d3159bfa7f42662fa1a957e35fb476e4042..f736899af2ca19b7f558ad89fe2b7c5a56513765 100644 (file)
--- a/PC/getpathp.c
+++ b/PC/getpathp.c
@@ -44,7 +44,7 @@
 
   * When Python is hosted in another exe (different directory, embedded via 
     COM, etc), the Python Home will not be deduced, so the core path from
-    the registry is used.  Other "application paths "in the registry are 
+    the registry is used.  Other "application paths" in the registry are 
     always read.
 
   * If Python can't find its home and there is no registry (eg, frozen
@@ -576,6 +576,40 @@ calculate_path(void)
                buf = strchr(buf, '\0');
        }
        *buf = '\0';
+       /* Now to pull one last hack/trick.  If sys.prefix is
+          empty, then try and find it somewhere on the paths
+          we calculated.  We scan backwards, as our general policy
+          is that Python core directories are at the *end* of
+          sys.path.  We assume that our "lib" directory is
+          on the path, and that our 'prefix' directory is
+          the parent of that.
+       */
+       if (*prefix=='\0') {
+               char lookBuf[MAXPATHLEN+1];
+               char *look = buf - 1; /* 'buf' is at the end of the buffer */
+               while (1) {
+                       int nchars;
+                       char *lookEnd = look;
+                       /* 'look' will end up one character before the
+                          start of the path in question - even if this
+                          is one character before the start of the buffer
+                       */
+                       while (*look != DELIM && look >= module_search_path)
+                               look--;
+                       nchars = lookEnd-look;
+                       strncpy(lookBuf, look+1, nchars);
+                       lookBuf[nchars] = '\0';
+                       /* Up one level to the parent */
+                       reduce(lookBuf);
+                       if (search_for_prefix(lookBuf, LANDMARK)) {
+                               break;
+                       }
+                       /* If we are out of paths to search - give up */
+                       if (look < module_search_path)
+                               break;
+                       look--;
+               }
+       }
 }