Replace hand-rolled IoError class with std::system_error

4 files changed, 30 insertions, 64 deletions

diff --git a/src/operations.cc b/src/operations.cc
index c799322..44e8d6b 100644
--- a/src/operations.cc
+++ b/src/operations.cc
@@ -23,6 +23,7 @@
 #include <experimental/optional>
 #include <memory>
 #include <new>
+#include <system_error>
 #include <type_traits>
 
 #include <dirent.h>
@@ -78,8 +79,8 @@ int Getattr(const char* const path, struct stat* output) noexcept {
     LOG(INFO) << "getattr: trimming leading slash";
     *output = root_->LinkStatAt(path + 1);
     return 0;
-  } catch (const IoError& e) {
-    return -e.number();
+  } catch (const std::system_error& e) {
+    return -e.code().value();
   }
 }
 
@@ -99,8 +100,8 @@ int Open(const char* const path, fuse_file_info* const file_info) {
             root_->OpenAt(path + 1, file_info->flags)));
   } catch (const std::bad_alloc&) {
     return -ENOMEM;
-  } catch (const IoError& e) {
-    return -e.number();
+  } catch (const std::system_error& e) {
+    return -e.code().value();
   }
 
   static_assert(sizeof(file_info->fh) == sizeof(uintptr_t),
@@ -125,8 +126,8 @@ int Create(const char* const path, const mode_t mode,
     file.reset(new File(root_->OpenAt(path + 1, file_info->flags, mode)));
   } catch (const std::bad_alloc&) {
     return -ENOMEM;
-  } catch (const IoError& e) {
-    return -e.number();
+  } catch (const std::system_error& e) {
+    return -e.code().value();
   }
 
   static_assert(sizeof(file_info->fh) == sizeof(uintptr_t),
@@ -158,8 +159,8 @@ int Opendir(const char* const path, fuse_file_info* const file_info) {
             root_->OpenAt(path + 1, O_DIRECTORY)));
   } catch (const std::bad_alloc&) {
     return -ENOMEM;
-  } catch (const IoError& e) {
-    return -e.number();
+  } catch (const std::system_error& e) {
+    return -e.code().value();
   }
 
   static_assert(sizeof(file_info->fh) == sizeof(uintptr_t),
@@ -192,8 +193,8 @@ int Readdir(const char*, void* const buffer, fuse_fill_dir_t filler,
         break;
       }
     }
-  } catch (const IoError& e) {
-    return -e.number();
+  } catch (const std::system_error& e) {
+    return -e.code().value();
   }
 
   return 0;
diff --git a/src/posix_extras.cc b/src/posix_extras.cc
index 2aeda7b..4093cc0 100644
--- a/src/posix_extras.cc
+++ b/src/posix_extras.cc
@@ -12,49 +12,34 @@
 // License for the specific language governing permissions and limitations under
 // the License.
 
-#define _XOPEN_SOURCE 700
-#undef _GNU_SOURCE
-
 #include "posix_extras.h"
 
 #include <cerrno>
 #include <experimental/optional>
 #include <stdexcept>
-#include <string>
-#include <vector>
+#include <system_error>
 
 #include <dirent.h>
 #include <fcntl.h>
 #include <glog/logging.h>
-#include <string.h>  // a POSIX header, not a libc one
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
 
 namespace scoville {
 
-std::string IoError::Message(const int number) noexcept {
-  try {
-    std::vector<char> text(64);
-    int strerror_result;
-    while ((strerror_result = strerror_r(number, text.data(), text.size())) ==
-           ERANGE) {
-      VLOG(1) << "IoError::Message: doubling message size from " << text.size();
-      text.resize(text.size() * 2);
-    }
+namespace {
 
-    if (strerror_result == 0) {
-      return std::string(text.begin(), text.end());
-    }
-  } catch (...) {
-  }
-  return "(could not generate error message)";
+std::system_error SystemError() {
+  return std::system_error(errno, std::system_category());
 }
 
+}  // namespace
+
 File::File(const char* const path, const int flags, const mode_t mode)
     : path_(path) {
   if ((fd_ = open(path, flags, mode)) == -1) {
-    throw IoError();
+    throw SystemError();
   }
   VLOG(1) << "opening file descriptor " << fd_;
 }
@@ -66,15 +51,14 @@ File::File(const File& other) : path_(other.path_), fd_(other.Duplicate()) {
 File::~File() noexcept {
   VLOG(1) << "closing file descriptor " << fd_;
   if (close(fd_) == -1) {
-    LOG(ERROR) << "failed to close file descriptor " << fd_ << ": "
-               << IoError::Message(errno);
+    LOG(ERROR) << "failed to close file descriptor " << fd_;
   }
 }
 
 struct stat File::Stat() const {
   struct stat result;
   if (fstat(fd_, &result) == -1) {
-    throw IoError();
+    throw SystemError();
   }
   return result;
 }
@@ -86,7 +70,7 @@ struct stat File::LinkStatAt(const char* const path) const {
 
   struct stat result;
   if (fstatat(fd_, path, &result, AT_SYMLINK_NOFOLLOW) == -1) {
-    throw IoError();
+    throw SystemError();
   }
   return result;
 }
@@ -98,7 +82,7 @@ File File::OpenAt(const char* const path, const int flags) const {
 
   File result;
   if ((result.fd_ = openat(fd_, path, flags)) == -1) {
-    throw IoError();
+    throw SystemError();
   }
   result.path_ = path_ + "/" + path;
   return result;
@@ -112,7 +96,7 @@ File File::OpenAt(const char* const path, const int flags,
 
   File result;
   if ((result.fd_ = openat(fd_, path, flags, mode)) == -1) {
-    throw IoError();
+    throw SystemError();
   }
   result.path_ = path_ + "/" + path;
   return result;
@@ -121,7 +105,7 @@ File File::OpenAt(const char* const path, const int flags,
 int File::Duplicate() const {
   int result;
   if ((result = dup(fd_)) == -1) {
-    throw IoError();
+    throw SystemError();
   }
   return result;
 }
@@ -131,22 +115,21 @@ Directory::Directory(const File& file) {
   // implementation, and should not otherwise be used by the application."  We
   // therefore need to grab an unmanaged copy of the file descriptor from file.
   if (!(stream_ = fdopendir(file.Duplicate()))) {
-    throw IoError();
+    throw SystemError();
   }
   rewinddir(stream_);
 }
 
 Directory::~Directory() noexcept {
   if (closedir(stream_) == -1) {
-    LOG(ERROR) << "failed to close directory stream: "
-               << IoError::Message(errno);
+    LOG(ERROR) << "failed to close directory stream";
   }
 }
 
 long Directory::offset() const {
   long result;
   if ((result = telldir(stream_)) == -1) {
-    throw IoError();
+    throw SystemError();
   }
   return result;
 }
@@ -160,7 +143,7 @@ std::experimental::optional<dirent> Directory::ReadOne() {
     if (errno == 0) {
       return std::experimental::nullopt;
     } else {
-      throw IoError();
+      throw SystemError();
     }
   }
   return *result;
diff --git a/src/posix_extras.h b/src/posix_extras.h
index 6f2fb37..b6dbdfd 100644
--- a/src/posix_extras.h
+++ b/src/posix_extras.h
@@ -15,9 +15,7 @@
 #ifndef POSIX_EXTRAS_H_
 #define POSIX_EXTRAS_H_
 
-#include <cerrno>
 #include <experimental/optional>
-#include <stdexcept>
 #include <string>
 
 #include <dirent.h>
@@ -26,23 +24,6 @@
 
 namespace scoville {
 
-class IoError : public std::runtime_error {
- public:
-  IoError() : IoError(errno) {}
-
-  explicit IoError(const int number)
-      : std::runtime_error(Message(number)), number_(number) {}
-
-  int number() const noexcept { return number_; }
-
-  // Converts an errno into a human-readable message, a la strerror(3).
-  // Thread-safe.
-  static std::string Message(int) noexcept;
-
- private:
-  int number_;
-};
-
 class File;
 
 // RAII wrapper for Unix directory streams.
diff --git a/src/scoville.cc b/src/scoville.cc
index 4cc563d..2b79cf6 100644
--- a/src/scoville.cc
+++ b/src/scoville.cc
@@ -15,6 +15,7 @@
 // this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #include <memory>
+#include <system_error>
 
 #include <fcntl.h>
 #include <gflags/gflags.h>
@@ -42,7 +43,7 @@ int main(int argc, char* argv[]) {
   const char* const root_path = argv[argc - 1];
   try {
     root.reset(new scoville::File(root_path, O_DIRECTORY));
-  } catch (const scoville::IoError& e) {
+  } catch (const std::system_error& e) {
     LOG(FATAL) << "scoville: bad mount point `" << root_path
                << "': " << e.what();
   }