commit 130e3d7204d2b2d3d2ba956c3243fbc0fb1cabe4
author Tom Cherry <tomcherry@google.com> Tue Aug 22 16:07:15 2017 -0700
committer Tom Cherry <tomcherry@google.com> Wed Aug 23 11:04:32 2017 -0700
tree 1aeef41d7c988db4d02026af31a3290e9288245f
parent 6de21f11125941ea1b94fdeec754bacea3916fd5

init: pass errors from one Result<T> to another better

Result<T> currently has two problems,
1) A failing Result<T> cannot be easily constructed from a Result<U>'s
error.
2) errno is lost when passing .error() through multiple Result<T>'s

This change fixes both problems having Result<T>::error() return a
ResultError class that contains the std::string error message and int
errno.

It additionally has ostream operators to continue to allow printing
the error string directly to an ostream and also to pass the errno
through to another Result<T> class via Error() creation.

Lastly, it provides a new constructor for Result<T> for ResultError,
such that a Result<T> can be constructed from Result<U>::error().

Test: boot bullhead, init unit tests
Change-Id: Id9614b727cdabd2f5498b0da0e598e9aff7d9ae0

init/util_test.cpp

diff --git a/init/util_test.cpp b/init/util_test.cpp
index 007d10e..3ae53a4 100644
--- a/init/util_test.cpp
+++ b/init/util_test.cpp
@@ -34,7 +34,7 @@
     auto file_contents = ReadFile("/proc/does-not-exist");
     EXPECT_EQ(ENOENT, errno);
     ASSERT_FALSE(file_contents);
-    EXPECT_EQ("open() failed: No such file or directory", file_contents.error());
+    EXPECT_EQ("open() failed: No such file or directory", file_contents.error_string());
 }
 
 TEST(util, ReadFileGroupWriteable) {
@@ -45,7 +45,7 @@
     EXPECT_NE(-1, fchmodat(AT_FDCWD, tf.path, 0620, AT_SYMLINK_NOFOLLOW)) << strerror(errno);
     auto file_contents = ReadFile(tf.path);
     ASSERT_FALSE(file_contents) << strerror(errno);
-    EXPECT_EQ("Skipping insecure file", file_contents.error());
+    EXPECT_EQ("Skipping insecure file", file_contents.error_string());
 }
 
 TEST(util, ReadFileWorldWiteable) {
@@ -56,7 +56,7 @@
     EXPECT_NE(-1, fchmodat(AT_FDCWD, tf.path, 0602, AT_SYMLINK_NOFOLLOW)) << strerror(errno);
     auto file_contents = ReadFile(tf.path);
     ASSERT_FALSE(file_contents) << strerror(errno);
-    EXPECT_EQ("Skipping insecure file", file_contents.error());
+    EXPECT_EQ("Skipping insecure file", file_contents.error_string());
 }
 
 TEST(util, ReadFileSymbolicLink) {
@@ -65,7 +65,7 @@
     auto file_contents = ReadFile("/charger");
     EXPECT_EQ(ELOOP, errno);
     ASSERT_FALSE(file_contents);
-    EXPECT_EQ("open() failed: Too many symbolic links encountered", file_contents.error());
+    EXPECT_EQ("open() failed: Too many symbolic links encountered", file_contents.error_string());
 }
 
 TEST(util, ReadFileSuccess) {
@@ -130,7 +130,7 @@
 
     decoded_uid = DecodeUid("toot");
     EXPECT_FALSE(decoded_uid);
-    EXPECT_EQ("getpwnam failed: No such file or directory", decoded_uid.error());
+    EXPECT_EQ("getpwnam failed: No such file or directory", decoded_uid.error_string());
 
     decoded_uid = DecodeUid("123");
     EXPECT_TRUE(decoded_uid);