2002-11-12 Andrew Cagney <ac131313@redhat.com>

	* utils.c (gdb_realpath): Rewrite.  Try, in order: realpath() with
	a constant buffer; cannonicalize_file_name(); realpath() with a
	pathconf() defined buffer, xstrdup().

1 files changed, 49 insertions, 16 deletions

diff --git a/gdb/utils.c b/gdb/utils.c
index 24a2819f492..b2a1d1810b4 100644
--- a/gdb/utils.c
+++ b/gdb/utils.c
@@ -2704,31 +2704,64 @@ string_to_core_addr (const char *my_string)
 char *
 gdb_realpath (const char *filename)
 {
+  /* Method 1: The system has a compile time upper bound on a filename
+     path.  Use that and realpath() to canonicalize the name.  This is
+     the most common case.  Note that, if there isn't a compile time
+     upper bound, you want to avoid realpath() at all costs.  */
 #if defined(HAVE_REALPATH)
+  {
 # if defined (PATH_MAX)
-  char buf[PATH_MAX];
+    char buf[PATH_MAX];
 #  define USE_REALPATH
 # elif defined (MAXPATHLEN)
-  char buf[MAXPATHLEN];
-#  define USE_REALPATH
-# elif defined (HAVE_UNISTD_H) && defined(HAVE_ALLOCA)
-  char *buf = alloca ((size_t)pathconf ("/", _PC_PATH_MAX));
+    char buf[MAXPATHLEN];
 #  define USE_REALPATH
 # endif
+# if defined (USE_REALPATH)
+    char *rp = realpath (filename, buf);
+    if (rp == NULL)
+      rp = filename;
+    return xstrdup (rp);
+  }
+# endif
 #endif /* HAVE_REALPATH */
 
-#if defined(USE_REALPATH)
-  char *rp = realpath (filename, buf);
-  return xstrdup (rp ? rp : filename);
-#elif defined(HAVE_CANONICALIZE_FILE_NAME)
-  char *rp = canonicalize_file_name (filename);
-  if (rp == NULL)
-    return xstrdup (filename);
-  else
-    return rp;
-#else
-  return xstrdup (filename);
+  /* Method 2: The host system (i.e., GNU) has the function
+     canonicalize_file_name() which malloc's a chunk of memory and
+     returns that, use that.  */
+#if defined(HAVE_CANONICALIZE_FILE_NAME)
+  {
+    char *rp = canonicalize_file_name (filename);
+    if (rp == NULL)
+      return xstrdup (filename);
+    else
+      return rp;
+  }
 #endif
+
+  /* Method 3: Now we're getting desperate!  The system doesn't have a
+     compile time buffer size and no alternative function.  Query the
+     OS, using pathconf(), for the buffer limit.  Care is needed
+     though, some systems do not limit PATH_MAX (return -1 for
+     pathconf()) making it impossible to pass a correctly sized buffer
+     to realpath() (it could always overflow).  On those systems, we
+     skip this.  */
+#if defined (HAVE_REALPATH) && defined (HAVE_UNISTD_H) && defined(HAVE_ALLOCA)
+  {
+    /* Find out the max path size.  */
+    long path_max = pathconf ("/", _PC_PATH_MAX);
+    if (path_max > 0)
+      {
+	/* PATH_MAX is bounded.  */
+	char *buf = alloca (path_max);
+	char *rp = realpath (filename, buf);
+	return xstrdup (rp ? rp : filename);
+      }
+  }
+#endif
+
+  /* This system is a lost cause, just dup the buffer.  */
+  return xstrdup (filename);
 }
 
 /* Return a copy of FILENAME, with its directory prefix canonicalized