gh-71052: Add Android build script and instructions (#116426)

1 files changed, 24 insertions, 11 deletions

diff --git a/configure.ac b/configure.ac
index cd17977..cdfafc2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4934,13 +4934,21 @@ fi
 if test "$ac_sys_system" = "Linux-android"; then
   # When these functions are used in an unprivileged process, they crash rather
   # than returning an error.
-  privileged_funcs="chroot initgroups setegid seteuid setgid setregid setresgid
-    setresuid setreuid setuid"
-
-  # These functions are unimplemented and always return an error.
-  unimplemented_funcs="sem_open sem_unlink"
+  blocked_funcs="chroot initgroups setegid seteuid setgid sethostname
+    setregid setresgid setresuid setreuid setuid"
+
+  # These functions are unimplemented and always return an error
+  # (https://android.googlesource.com/platform/system/sepolicy/+/refs/heads/android13-release/public/domain.te#1044)
+  blocked_funcs="$blocked_funcs sem_open sem_unlink"
+
+  # Before API level 23, when fchmodat is called with the unimplemented flag
+  # AT_SYMLINK_NOFOLLOW, instead of returning ENOTSUP as it should, it actually
+  # follows the symlink.
+  if test "$ANDROID_API_LEVEL" -lt 23; then
+    blocked_funcs="$blocked_funcs fchmodat"
+  fi
 
-  for name in $privileged_funcs $unimplemented_funcs; do
+  for name in $blocked_funcs; do
     AS_VAR_PUSHDEF([func_var], [ac_cv_func_$name])
     AS_VAR_SET([func_var], [no])
     AS_VAR_POPDEF([func_var])
@@ -5303,11 +5311,16 @@ then
   ])
 fi
 
-AC_CHECK_FUNCS([clock_nanosleep], [], [
-    AC_CHECK_LIB([rt], [clock_nanosleep], [
-        AC_DEFINE([HAVE_CLOCK_NANOSLEEP], [1])
-    ])
-])
+# On Android before API level 23, clock_nanosleep returns the wrong value when
+# interrupted by a signal (https://issuetracker.google.com/issues/216495770).
+if ! { test "$ac_sys_system" = "Linux-android" &&
+       test "$ANDROID_API_LEVEL" -lt 23; }; then
+  AC_CHECK_FUNCS([clock_nanosleep], [], [
+      AC_CHECK_LIB([rt], [clock_nanosleep], [
+          AC_DEFINE([HAVE_CLOCK_NANOSLEEP], [1])
+      ])
+  ])
+fi
 
 AC_CHECK_FUNCS([nanosleep], [], [
     AC_CHECK_LIB([rt], [nanosleep], [