Expand one level of symbolic link in sys.argv[0] before inserting its

dirname in sys.path.  This means that you can create a symbolic link
foo in /usr/local/bin pointing to /usr/yourname/src/foo/foo.py, and
then invoking foo will insert /usr/yourname/src/foo in sys.path, not
/usr/local/bin.  This makes it easier to have multifile programs
(before, the program would have to do an os.readlink(sys.argv[0])
itself and insert the resulting directory in sys.path -- Grail does
this).

Note that the expansion is only used for sys.path; sys.argv[0] is
still the original, unadorned filename (/usr/local/bin/foo in the
example).

diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index c1eaeede5e3e5381eeeb017fb81d5bf72fb42bb3..69cb7aaccbf6456024ea9de24a699ea1a65a682a 100644 (file)
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -54,6 +54,10 @@ Data members:
 object *sys_trace, *sys_profile;
 int sys_checkinterval = 10;
 
+#if HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
 static object *sysdict;
 
 #ifdef MS_COREDLL
@@ -387,35 +391,64 @@ setpythonargv(argc, argv)
        if (sysset("argv", av) != 0)
                fatal("can't assign sys.argv");
        if (path != NULL) {
+               char *argv0 = argv[0];
                char *p = NULL;
                int n = 0;
                object *a;
+#ifdef HAVE_READLINK
+               char link[MAXPATHLEN+1];
+               char argv0copy[2*MAXPATHLEN+1];
+               int nr = 0;
+               if (argc > 0 && argv0 != NULL)
+                       nr = readlink(argv0, link, MAXPATHLEN);
+               if (nr > 0) {
+                       /* It's a symlink */
+                       link[nr] = '\0';
+                       if (link[0] == SEP)
+                               argv0 = link; /* Link to absolute path */
+                       else if (strchr(link, SEP) == NULL)
+                               ; /* Link without path */
+                       else {
+                               /* Must join(dirname(argv0), link) */
+                               char *q = strrchr(argv0, SEP);
+                               if (q == NULL)
+                                       argv0 = link; /* argv0 without path */
+                               else {
+                                       /* Must make a copy */
+                                       strcpy(argv0copy, argv0);
+                                       q = strrchr(argv0copy, SEP);
+                                       strcpy(q+1, link);
+                                       argv0 = argv0copy;
+                               }
+                       }
+               }
+#endif /* HAVE_READLINK */
 #if SEP == '\\' /* Special case for MS filename syntax */
-               if (argc > 0 && argv[0] != NULL) {
+               if (argc > 0 && argv0 != NULL) {
                        char *q;
-                       p = strrchr(argv[0], SEP);
+                       p = strrchr(argv0, SEP);
                        /* Test for alternate separator */
-                       q = strrchr(p ? p : argv[0], '/');
+                       q = strrchr(p ? p : argv0, '/');
                        if (q != NULL)
                                p = q;
                        if (p != NULL) {
-                               n = p + 1 - argv[0];
+                               n = p + 1 - argv0;
                                if (n > 1 && p[-1] != ':')
                                        n--; /* Drop trailing separator */
                        }
                }
 #else /* All other filename syntaxes */
-               if (argc > 0 && argv[0] != NULL)
-                       p = strrchr(argv[0], SEP);
+               if (argc > 0 && argv0 != NULL)
+                       p = strrchr(argv0, SEP);
                if (p != NULL) {
-                       n = p + 1 - argv[0];
+                       n = p + 1 - argv0;
 #if SEP == '/' /* Special case for Unix filename syntax */
                        if (n > 1)
                                n--; /* Drop trailing separator */
 #endif /* Unix */
                }
 #endif /* All others */
-               a = newsizedstringobject(argv[0], n);
+               a = newsizedstringobject(argv0, n);
                if (a == NULL)
                        fatal("no mem for sys.path insertion");
                if (inslistitem(path, 0, a) < 0)