3 files changed, 86 insertions, 7 deletions
diff --git a/libc/include/android/api-level.h b/libc/include/android/api-level.h
index 50cb61a6b..bcddddd59 100644
--- a/libc/include/android/api-level.h
+++ b/libc/include/android/api-level.h
@@ -29,6 +29,13 @@
 #pragma once
 
 /**
+ * @defgroup apilevels API Levels
+ *
+ * Defines functions and constants for working with Android API levels.
+ * @{
+ */
+
+/**
  * @file android/api-level.h
  * @brief Functions and constants for dealing with multiple API levels.
  *
@@ -50,9 +57,40 @@ __BEGIN_DECLS
 /* This #ifndef should never be true except when doxygen is generating docs. */
 #ifndef __ANDROID_API__
 /**
- * `__ANDROID_API__` is the API level being targeted. For the OS,
- * this is `__ANDROID_API_FUTURE__`. For the NDK, this is set by the
- * compiler system based on the API level you claimed to target. See
+ * `__ANDROID_API__` is the [API
+ * level](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
+ * this code is being built for. The resulting binaries are only guaranteed to
+ * be compatible with devices which have an API level greater than or equal to
+ * `__ANDROID_API__`.
+ *
+ * For NDK and APEX builds, this macro will always be defined. It is set
+ * automatically by Clang using the version suffix that is a part of the target
+ * name. For example, `__ANDROID_API__` will be 24 when Clang is given the
+ * argument `-target aarch64-linux-android24`.
+ *
+ * For non-APEX OS code, this defaults to  __ANDROID_API_FUTURE__.
+ *
+ * The value of `__ANDROID_API__` can be compared to the named constants in
+ * `<android/api-level.h>`.
+ *
+ * The interpretation of `__ANDROID_API__` is similar to the AndroidManifest.xml
+ * `minSdkVersion`. In most cases `__ANDROID_API__` will be identical to
+ * `minSdkVersion`, but as it is a build time constant it is possible for
+ * library code to use a different value than the app it will be included in.
+ * When libraries and applications build for different API levels, the
+ * `minSdkVersion` of the application must be at least as high as the highest
+ * API level used by any of its libraries which are loaded unconditionally.
+ *
+ * Note that in some cases the resulting binaries may load successfully on
+ * devices with an older API level. That behavior should not be relied upon,
+ * even if you are careful to avoid using new APIs, as the toolchain may make
+ * use of new features by default. For example, additional FORTIFY features may
+ * implicitly make use of new APIs, SysV hashes may be omitted in favor of GNU
+ * hashes to improve library load times, or relocation packing may be enabled to
+ * reduce binary size.
+ *
+ * See android_get_device_api_level(),
+ * android_get_application_target_sdk_version() and
  * https://android.googlesource.com/platform/bionic/+/master/docs/defines.md.
  */
 #define __ANDROID_API__ __ANDROID_API_FUTURE__
@@ -114,9 +152,9 @@ __BEGIN_DECLS
 #define __ANDROID_API_S__ 31
 
 /**
- * Returns the `targetSdkVersion` of the caller, or `__ANDROID_API_FUTURE__`
- * if there is no known target SDK version (for code not running in the
- * context of an app).
+ * Returns the `targetSdkVersion` of the caller, or `__ANDROID_API_FUTURE__` if
+ * there is no known target SDK version (for code not running in the context of
+ * an app).
  *
  * The returned values correspond to the named constants in `<android/api-level.h>`,
  * and is equivalent to the AndroidManifest.xml `targetSdkVersion`.
@@ -148,3 +186,5 @@ int android_get_device_api_level() __INTRODUCED_IN(29);
 #endif
 
 __END_DECLS
+
+/** @} */
diff --git a/libc/include/android/fdsan.h b/libc/include/android/fdsan.h
index 83b9318ba..e23de85d3 100644
--- a/libc/include/android/fdsan.h
+++ b/libc/include/android/fdsan.h
@@ -186,7 +186,8 @@ enum android_fdsan_error_level android_fdsan_get_error_level() __INTRODUCED_IN(2
  * Set the error level and return the previous state.
  *
  * Error checking is automatically disabled in the child of a fork, to maintain
- * compatibility with code that forks, blindly closes FDs, and then execs.
+ * compatibility with code that forks, closes all file descriptors, and then
+ * execs.
  *
  * In cases such as the zygote, where the child has no intention of calling
  * exec, call this function to reenable fdsan checks.
diff --git a/libc/include/android/legacy_unistd_inlines.h b/libc/include/android/legacy_unistd_inlines.h
new file mode 100644
index 000000000..4a5206b88
--- /dev/null
+++ b/libc/include/android/legacy_unistd_inlines.h
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <sys/cdefs.h>
+
+#if __ANDROID_API__ < 28
+
+#define __BIONIC_SWAB_INLINE static __inline
+#include <bits/swab.h>
+
+#endif