simplewallet: Use default log file name when executable's file path is unknown

Default to "simplewallet.log" in current directory when file path isn't
obtained from epee.

In this situation previously, it defaulted to the file name of ".log"
("" + ".log") in the current directory.
(Thanks to @sammy007 for reporting bug.)

An earlier version yet used "" + "/" + ".log" = "/.log", which resulted
in silently not logging in most cases, due to lack of permission.

Test:
  PATH=$PATH:</path/to/simplewallet/folder> && simplewallet --wallet-file /dev/null

This results in epee not finding the executable's file path, so
simplewallet will now use a default log filename.

1 files changed, 21 insertions, 3 deletions

diff --git a/src/simplewallet/simplewallet.cpp b/src/simplewallet/simplewallet.cpp
index ed3ab4470..0c91d9787 100644
--- a/src/simplewallet/simplewallet.cpp
+++ b/src/simplewallet/simplewallet.cpp
@@ -1815,8 +1815,23 @@ int main(int argc, char* argv[])
   command_line::add_arg(desc_params, arg_log_level);
 
   bf::path default_log {log_space::log_singletone::get_default_log_folder()};
-  default_log /= log_space::log_singletone::get_default_log_file();
-  std::cout << sw::tr("default_log: ") << default_log << ENDL;
+  std::string log_file_name = log_space::log_singletone::get_default_log_file();
+  if (log_file_name.empty())
+  {
+    // Sanity check: File path should also be empty if file name is. If not,
+    // this would be a problem in epee's discovery of current process's file
+    // path.
+    if (! default_log.empty())
+    {
+      fail_msg_writer() << sw::tr("Unexpected empty log file name in presence of non-empty file path");
+      return false;
+    }
+    // epee didn't find path to executable from argv[0], so use this default file name.
+    log_file_name = "simplewallet.log";
+    // The full path will use cwd because epee also returned an empty default log folder.
+  }
+  default_log /= log_file_name;
+
   command_line::add_arg(desc_params, arg_log_file, default_log.string());
 
   command_line::add_arg(desc_params, arg_restore_deterministic_wallet );
@@ -1861,7 +1876,9 @@ int main(int argc, char* argv[])
     return 0;
 
   // log_file_path
-  //   default: <simplewallet_path>/simplewallet.log
+  //   default: < argv[0] directory >/simplewallet.log
+  //     so if ran as "simplewallet" (no path), log file will be in cwd
+  //
   //   if log-file argument given:
   //     absolute path
   //     relative path: relative to cwd
@@ -1884,6 +1901,7 @@ int main(int argc, char* argv[])
   if(command_line::has_arg(vm, arg_log_level))
     log_level = command_line::get_arg(vm, arg_log_level);
   LOG_PRINT_L0("Setting log level = " << log_level);
+  LOG_PRINT_L0(sw::tr("default_log: ") << default_log.string());
   message_writer(epee::log_space::console_color_white, true) << boost::format(sw::tr("Logging at log level %d to %s")) %
     log_level % log_file_path.string();
   log_space::get_set_log_detalisation_level(true, log_level);