Keep libpath length non-negative [Bug #16784]

When runtime_libruby_path does not include '/', it attempts to call
rb_str_resize with negative length. This change makes sure that the
length non-negative.

Co-Authored-By: xtkoba (Tee KOBAYASHI) <xtkoba+ruby@gmail.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/ruby.c b/ruby.c
index b94937b0da..f297c2b0a8 100644
--- a/ruby.c
+++ b/ruby.c
@@ -671,8 +671,11 @@ ruby_init_loadpath(void)
 	    p = p2;
 	}
 #endif
+        baselen = p - libpath;
+    }
+    else {
+        baselen = 0;
     }
-    baselen = p - libpath;
     rb_str_resize(sopath, baselen);
     libpath = RSTRING_PTR(sopath);
 #define PREFIX_PATH() sopath