Reject -L "", -L native=, and other empty search paths.

mk/main.mk

@@ -290,6 +290,7 @@ LLVM_VERSION_$(1)=$$(shell "$$(LLVM_CONFIG_$(1))" --version)
 LLVM_BINDIR_$(1)=$$(shell "$$(LLVM_CONFIG_$(1))" --bindir)
 LLVM_INCDIR_$(1)=$$(shell "$$(LLVM_CONFIG_$(1))" --includedir)
 LLVM_LIBDIR_$(1)=$$(shell "$$(LLVM_CONFIG_$(1))" --libdir)
+LLVM_LIBDIR_RUSTFLAGS_$(1)=-L "$$(LLVM_LIBDIR_$(1))"
 LLVM_LIBS_$(1)=$$(shell "$$(LLVM_CONFIG_$(1))" --libs $$(LLVM_COMPONENTS))
 LLVM_LDFLAGS_$(1)=$$(shell "$$(LLVM_CONFIG_$(1))" --ldflags)
 # On FreeBSD, it may search wrong headers (that are for pre-installed LLVM),

mk/target.mk

@@ -84,7 +84,7 @@ $$(TLIB$(1)_T_$(2)_H_$(3))/stamp.$(4): \
 	    $$(subst @,,$$(STAGE$(1)_T_$(2)_H_$(3))) \
 		$$(RUST_LIB_FLAGS_ST$(1)) \
 		-L "$$(RT_OUTPUT_DIR_$(2))" \
-		-L "$$(LLVM_LIBDIR_$(2))" \
+		$$(LLVM_LIBDIR_RUSTFLAGS_$(2)) \
 		$$(LLVM_STDCPP_RUSTFLAGS_$(2)) \
 		$$(RUSTFLAGS_$(4)) \
 		--out-dir $$(@D) \

mk/tests.mk

@@ -372,7 +372,7 @@ $(3)/stage$(1)/test/$(4)test-$(2)$$(X_$(2)): \
 	$(Q)CFG_LLVM_LINKAGE_FILE=$$(LLVM_LINKAGE_PATH_$(3)) \
 	    $$(subst @,,$$(STAGE$(1)_T_$(2)_H_$(3))) -o $$@ $$< --test \
 		-L "$$(RT_OUTPUT_DIR_$(2))" \
-		-L "$$(LLVM_LIBDIR_$(2))" \
+		$$(LLVM_LIBDIR_RUSTFLAGS_$(2)) \
 		$$(RUSTFLAGS_$(4))
 
 endef

src/librustc/session/search_paths.rs

@@ -10,6 +10,7 @@
 
 use std::slice;
 use std::path::{Path, PathBuf};
+use session::early_error;
 
 #[derive(Clone, Debug)]
 pub struct SearchPaths {
@@ -50,6 +51,9 @@ impl SearchPaths {
         } else {
             (PathKind::All, path)
         };
+        if path.is_empty() {
+            early_error("empty search path given via `-L`");
+        }
         self.paths.push((kind, PathBuf::new(path)));
     }
 

src/test/compile-fail/manual-link-bad-search-path.rs

@@ -0,0 +1,15 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// compile-flags:-L native=
+// error-pattern: empty search path given via `-L`
+
+fn main() {
+}