commit 557946e57c375b05deb5ba07b739f27abc70697e
author Tom Cherry <tomcherry@google.com> Tue Aug 01 13:50:23 2017 -0700
committer Tom Cherry <tomcherry@google.com> Mon Aug 14 14:07:39 2017 -0700
tree a073dadfaa7529739187ae7264abc21b881c8b97
parent 11a3aeeae3dc887b889d4086d4d26d95c324c08d

init: use Result<T> for builtin functions

We currently throw out the return values from builtin functions and
occasionally log errors with no supporting context.  This change uses
the newly introduced Result<T> class to communicate a successful result
or an error back to callers in order to print an error with clear
context when a builtin fails.

Example:

init: Command 'write /sys/class/leds/vibrator/trigger transient' action=init (/init.rc:245) took 0ms and failed: Unable to write to file '/sys/class/leds/vibrator/trigger': open() failed: No such file or directory

Test: boot bullhead
Merged-In: Idc18f331d2d646629c6093c1e0f2996cf9b42aec
Change-Id: Idc18f331d2d646629c6093c1e0f2996cf9b42aec

init/action.cpp

diff --git a/init/action.cpp b/init/action.cpp
index 4ec5f17..671e285 100644
--- a/init/action.cpp
+++ b/init/action.cpp
@@ -31,14 +31,13 @@
 Command::Command(BuiltinFunction f, const std::vector<std::string>& args, int line)
     : func_(f), args_(args), line_(line) {}
 
-int Command::InvokeFunc() const {
+Result<Success> Command::InvokeFunc() const {
     std::vector<std::string> expanded_args;
     expanded_args.resize(args_.size());
     expanded_args[0] = args_[0];
     for (std::size_t i = 1; i < args_.size(); ++i) {
         if (!expand_props(args_[i], &expanded_args[i])) {
-            LOG(ERROR) << args_[0] << ": cannot expand '" << args_[i] << "'";
-            return -EINVAL;
+            return Error() << "cannot expand '" << args_[i] << "'";
         }
     }
 
@@ -92,17 +91,17 @@
 
 void Action::ExecuteCommand(const Command& command) const {
     android::base::Timer t;
-    int result = command.InvokeFunc();
-
+    auto result = command.InvokeFunc();
     auto duration = t.duration();
+
     // Any action longer than 50ms will be warned to user as slow operation
     if (duration > 50ms || android::base::GetMinimumLogSeverity() <= android::base::DEBUG) {
         std::string trigger_name = BuildTriggersString();
         std::string cmd_str = command.BuildCommandString();
 
         LOG(INFO) << "Command '" << cmd_str << "' action=" << trigger_name << " (" << filename_
-                  << ":" << command.line() << ") returned " << result << " took "
-                  << duration.count() << "ms.";
+                  << ":" << command.line() << ") took " << duration.count() << "ms and "
+                  << (result ? "succeeded" : "failed: " + result.error());
     }
 }