Fix GNU/POSIX basename headers.

Including glibc's <libgen.h> will result in the user getting the POSIX
version of basename always, regardless of when it is included relative
to <string.h>. Prior to this patch, our implementation would result in
the one that's included first winning.

Bug: http://b/25459151
Change-Id: Id4aaf1670dad317d6bbc05763a84ee87596e8e59

libc/include/libgen.h

@@ -32,18 +32,19 @@
 #include <sys/cdefs.h>
 #include <sys/types.h>
 
+
 __BEGIN_DECLS
 
-#if !defined(__bionic_using_gnu_basename)
 /*
- * <string.h> gets you the GNU basename.
- * <libgen.h> the POSIX one.
- * Note that our "POSIX" one has the wrong argument cv-qualifiers, but doesn't
- * modify its input and uses thread-local storage for the result if necessary.
+ * Including <string.h> will get you the GNU basename, unless <libgen.h> is
+ * included, either before or after including <string.h>.
+ *
+ * Note that this has the wrong argument cv-qualifiers, but doesn't modify its
+ * input and uses thread-local storage for the result if necessary.
  */
-extern char* basename(const char*);
-#define __bionic_using_posix_basename
-#endif
+extern char* __posix_basename(const char*) __RENAME(basename);
+
+#define basename __posix_basename
 
 /* This has the wrong argument cv-qualifiers, but doesn't modify its input and uses thread-local storage for the result if necessary. */
 extern char* dirname(const char*);

libc/include/string.h

@@ -115,18 +115,18 @@ extern size_t strxfrm(char* __restrict, const char* __restrict, size_t);
 extern int    strcoll_l(const char *, const char *, locale_t) __purefunc;
 extern size_t strxfrm_l(char* __restrict, const char* __restrict, size_t, locale_t);
 
-#if defined(__USE_GNU) && !defined(__bionic_using_posix_basename)
+#if defined(__USE_GNU) && !defined(basename)
 /*
  * glibc has a basename in <string.h> that's different to the POSIX one in <libgen.h>.
  * It doesn't modify its argument, and in C++ it's const-correct.
  */
+
 #if defined(__cplusplus)
 extern "C++" char* basename(char*) __RENAME(__gnu_basename) __nonnull((1));
 extern "C++" const char* basename(const char*) __RENAME(__gnu_basename) __nonnull((1));
 #else
 extern char* basename(const char*) __RENAME(__gnu_basename) __nonnull((1));
 #endif
-#define __bionic_using_gnu_basename
 #endif
 
 extern void* __memchr_chk(const void*, int, size_t, size_t);

tests/Android.mk

@@ -63,6 +63,7 @@ libBionicStandardTests_src_files := \
     getcwd_test.cpp \
     inttypes_test.cpp \
     libc_logging_test.cpp \
+    libgen_basename_test.cpp \
     libgen_test.cpp \
     locale_test.cpp \
     malloc_test.cpp \

tests/libgen_basename_test.cpp

@@ -0,0 +1,89 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _GNU_SOURCE
+  #define _GNU_SOURCE 1
+#endif
+
+#include <string.h>
+
+#if defined(basename)
+  #error basename should not be defined at this point
+#endif
+
+static const char* gnu_basename(const char* in) {
+  return basename(in);
+}
+
+#include <libgen.h>
+
+#if !defined(basename)
+  #error basename should be defined at this point
+#endif
+
+static char* posix_basename(char* in) {
+  return basename(in);
+}
+
+#include <errno.h>
+#include <gtest/gtest.h>
+
+static void __TestGnuBasename(const char* in, const char* expected_out, int line) {
+  const char* out = gnu_basename(in);
+  ASSERT_STREQ(expected_out, out) << "(" << line << "): " << in << std::endl;
+  ASSERT_EQ(0, errno) << "(" << line << "): " << in << std::endl;
+}
+
+static void __TestPosixBasename(const char* in, const char* expected_out, int line) {
+  char* writable_in = (in != NULL) ? strdup(in) : NULL;
+  errno = 0;
+  const char* out = posix_basename(&writable_in[0]);
+  ASSERT_STREQ(expected_out, out) << "(" << line << "): " << in << std::endl;
+  ASSERT_EQ(0, errno) << "(" << line << "): " << in << std::endl;
+  free(writable_in);
+}
+
+#define TestGnuBasename(in, expected) __TestGnuBasename(in, expected, __LINE__)
+#define TestPosixBasename(in, expected) __TestPosixBasename(in, expected, __LINE__)
+
+TEST(libgen_basename, gnu_basename) {
+  // GNU's basename doesn't accept NULL
+  // TestGnuBasename(NULL, ".");
+  TestGnuBasename("", "");
+  TestGnuBasename("/usr/lib", "lib");
+  TestGnuBasename("/system/bin/sh/", "");
+  TestGnuBasename("/usr/", "");
+  TestGnuBasename("usr", "usr");
+  TestGnuBasename("/", "");
+  TestGnuBasename(".", ".");
+  TestGnuBasename("..", "..");
+  TestGnuBasename("///", "");
+  TestGnuBasename("//usr//lib//", "");
+}
+
+TEST(libgen_basename, posix_basename) {
+  TestPosixBasename(NULL, ".");
+  TestPosixBasename("", ".");
+  TestPosixBasename("/usr/lib", "lib");
+  TestPosixBasename("/system/bin/sh/", "sh");
+  TestPosixBasename("/usr/", "usr");
+  TestPosixBasename("usr", "usr");
+  TestPosixBasename("/", "/");
+  TestPosixBasename(".", ".");
+  TestPosixBasename("..", "..");
+  TestPosixBasename("///", "/");
+  TestPosixBasename("//usr//lib//", "lib");
+}

tests/libgen_test.cpp

@@ -19,15 +19,6 @@
 #include <errno.h>
 #include <gtest/gtest.h>
 
-static void TestBasename(const char* in, const char* expected_out) {
-  char* writable_in = (in != NULL) ? strdup(in) : NULL;
-  errno = 0;
-  const char* out = basename(&writable_in[0]);
-  ASSERT_STREQ(expected_out, out) << in;
-  ASSERT_EQ(0, errno) << in;
-  free(writable_in);
-}
-
 static void TestDirname(const char* in, const char* expected_out) {
   char* writable_in = (in != NULL) ? strdup(in) : NULL;
   errno = 0;
@@ -37,21 +28,6 @@ static void TestDirname(const char* in, const char* expected_out) {
   free(writable_in);
 }
 
-// Do not use basename as the test name, it's defined to another value in glibc
-// so leads to a differently named test on host versus target architectures.
-TEST(libgen, posix_basename) {
-  TestBasename(NULL, ".");
-  TestBasename("", ".");
-  TestBasename("/usr/lib", "lib");
-  TestBasename("/usr/", "usr");
-  TestBasename("usr", "usr");
-  TestBasename("/", "/");
-  TestBasename(".", ".");
-  TestBasename("..", "..");
-  TestBasename("///", "/");
-  TestBasename("//usr//lib//", "lib");
-}
-
 TEST(libgen, dirname) {
   TestDirname(NULL, ".");
   TestDirname("", ".");