Implement throw_generic_error() and throw_system_error()

8 files changed, 169 insertions, 112 deletions

diff --git a/butl/fdstream.cxx b/butl/fdstream.cxx
index 41dd1f5..d841cc2 100644
--- a/butl/fdstream.cxx
+++ b/butl/fdstream.cxx
@@ -71,14 +71,36 @@ namespace butl
     throw ios_base::failure (m != nullptr ? m : e.message ().c_str ());
   }
 
+  // Throw system_error with generic_category.
+  //
   static inline void
-  throw_ios_failure (int ev, const char* m = nullptr)
+  throw_ios_failure (int errno_code, const char* m = nullptr)
   {
-    error_code ec (ev, system_category ());
+    error_code ec (errno_code, generic_category ());
     throw_ios_failure<is_base_of<system_error, ios_base::failure>::value> (
       ec, m);
   }
 
+#ifdef _WIN32
+  // Throw system_error with system_category.
+  //
+  static inline void
+  throw_ios_system_failure (int system_code)
+  {
+    // Here we work around MinGW libstdc++ that interprets Windows system error
+    // codes (for example those returned by GetLastError()) as errno codes.
+    //
+    // Note that the resulting system_error description will have ': Success.'
+    // suffix that is stripped by our custom operator<<(ostream, exception).
+    //
+    error_code ec (0, system_category ());
+    string m (win32::error_msg (system_code));
+
+    throw_ios_failure<is_base_of<system_error, ios_base::failure>::value> (
+      ec, m.c_str ());
+  }
+#endif
+
   // auto_fd
   //
   void auto_fd::
@@ -905,7 +927,7 @@ namespace butl
     {
       HANDLE h (reinterpret_cast<HANDLE> (_get_osfhandle (fd)));
       if (h == INVALID_HANDLE_VALUE)
-        throw_ios_failure (EIO, "unable to obtain file handle");
+        throw_ios_failure (errno); // EBADF (POSIX value).
 
       return h;
     };
@@ -921,7 +943,7 @@ namespace butl
 
     DWORD f;
     if (!GetHandleInformation (handle (fd), &f))
-      throw_ios_failure (EIO, last_error_msg ().c_str ());
+      throw_ios_system_failure (GetLastError ());
 
     // If the source handle is inheritable then no flag copy is required (as
     // the duplicate handle will be inheritable by default).
@@ -933,7 +955,7 @@ namespace butl
 
     auto_fd nfd (dup ());
     if (!SetHandleInformation (handle (nfd.get ()), HANDLE_FLAG_INHERIT, 0))
-      throw_ios_failure (EIO, last_error_msg ().c_str ());
+      throw_ios_system_failure (GetLastError ());
 
     return nfd;
   }
@@ -975,6 +997,10 @@ namespace butl
     }
     catch (const system_error& e)
     {
+      // Make sure that the error denotes errno portable code.
+      //
+      assert (e.code ().category () == generic_category ());
+
       errno = e.code ().value ();
       return -1;
     }
@@ -999,7 +1025,7 @@ namespace butl
     //
     int r (_setmode (fd, m == fdstream_mode::binary ? _O_BINARY : _O_TEXT));
     if (r == -1)
-      throw_ios_failure (errno);
+      throw_ios_failure (errno); // EBADF or EINVAL (POSIX values).
 
     return fdstream_mode::blocking |
       ((r & _O_BINARY) == _O_BINARY
diff --git a/butl/filesystem.cxx b/butl/filesystem.cxx
index e881417..1873bfa 100644
--- a/butl/filesystem.cxx
+++ b/butl/filesystem.cxx
@@ -37,6 +37,7 @@
 #include <system_error>
 
 #include <butl/path>
+#include <butl/utility>      // throw_generic_error()
 #include <butl/fdstream>
 #include <butl/small-vector>
 
@@ -75,7 +76,7 @@ namespace butl
       if (errno == ENOENT || errno == ENOTDIR)
         return make_pair (false, entry_type::unknown);
       else
-        throw system_error (errno, system_category ());
+        throw_generic_error (errno);
     }
 
     auto m (s.st_mode);
@@ -129,7 +130,7 @@ namespace butl
         if (errno == ENOENT || errno == ENOTDIR)
           return make_pair (false, entry_type::unknown);
         else
-          throw system_error (errno, system_category ());
+          throw_generic_error (errno);
       }
 
       auto m (s.st_mode);
@@ -166,7 +167,7 @@ namespace butl
       if (e == EEXIST && dir_exists (p))
         return mkdir_status::already_exists;
       else
-        throw system_error (e, system_category ());
+        throw_generic_error (e);
     }
 
     return mkdir_status::success;
@@ -202,7 +203,7 @@ namespace butl
       else if (errno == ENOTEMPTY || errno == EEXIST)
         r = rmdir_status::not_empty;
       else if (!ignore_error)
-        throw system_error (errno, system_category ());
+        throw_generic_error (errno);
     }
 
     return r;
@@ -229,8 +230,9 @@ namespace butl
       rmdir_status r (try_rmdir (p));
 
       if (r != rmdir_status::success && !ignore_error)
-        throw system_error (r == rmdir_status::not_empty ? ENOTEMPTY : ENOENT,
-                            system_category ());
+        throw_generic_error (r == rmdir_status::not_empty
+                             ? ENOTEMPTY
+                             : ENOENT);
     }
   }
 
@@ -251,7 +253,7 @@ namespace butl
       if (errno == ENOENT || errno == ENOTDIR)
         r = rmfile_status::not_exist;
       else if (!ignore_error)
-        throw system_error (errno, system_category ());
+        throw_generic_error (errno);
     }
 
     return r;
@@ -262,14 +264,14 @@ namespace butl
   mksymlink (const path& target, const path& link, bool)
   {
     if (symlink (target.string ().c_str (), link.string ().c_str ()) == -1)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
   }
 
   void
   mkhardlink (const path& target, const path& link, bool)
   {
     if (::link (target.string ().c_str (), link.string ().c_str ()) == -1)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
   }
 
 #else
@@ -277,7 +279,7 @@ namespace butl
   void
   mksymlink (const path&, const path&, bool)
   {
-    throw system_error (ENOSYS, system_category (), "symlinks not supported");
+    throw_generic_error (ENOSYS, "symlinks not supported");
   }
 
   void
@@ -288,14 +290,10 @@ namespace butl
       if (!CreateHardLinkA (link.string ().c_str (),
                             target.string ().c_str (),
                             nullptr))
-      {
-        string e (win32::last_error_msg ());
-        throw system_error (EIO, system_category (), e);
-      }
+        throw_system_error (GetLastError ());
     }
     else
-      throw system_error (
-        ENOSYS, system_category (), "directory hard links not supported");
+      throw_generic_error (ENOSYS, "directory hard links not supported");
   }
 #endif
 
@@ -362,7 +360,7 @@ namespace butl
       // Note that our custom operator<<(ostream, exception) doesn't strip this
       // suffix. This is a temporary code after all.
       //
-      throw system_error (EIO, system_category (), e.what ());
+      throw_generic_error (EIO, e.what ());
     }
   }
 
@@ -450,7 +448,7 @@ namespace butl
 #ifndef _WIN32
 
     if (!ovr && path_entry (to).first)
-      throw system_error (EEXIST, system_category ());
+      throw_generic_error (EEXIST);
 
     if (::rename (f, t) == 0) // POSIX implementation.
       return;
@@ -459,7 +457,7 @@ namespace butl
     // move the file ourselves.
     //
     if (errno != EXDEV)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 
     // Note that cpfile() follows symlinks, so we need to remove destination if
     // exists.
@@ -474,7 +472,7 @@ namespace butl
     //
     struct stat s;
     if (stat (f, &s) != 0)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 
     timeval times[2];
     times[0].tv_sec = s.st_atime;
@@ -483,7 +481,7 @@ namespace butl
     times[1].tv_usec = mnsec<struct stat> (&s, true) / 1000;
 
     if (utimes (t, times) != 0)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 
     // Finally, remove the source file.
     //
@@ -496,13 +494,8 @@ namespace butl
     //
     auto te (path_entry (to));
 
-    // Note that it would be nicer to just pass standard error codes to
-    // system_error ctors below, but their error descriptions horrifies for
-    // msvcrt. Actually they just don't match the semantics. The resulted error
-    // description is also not ideal (see below).
-    //
     if (!ovr && te.first)
-      throw system_error (EEXIST, system_category (), "file exists");
+      throw_generic_error (EEXIST);
 
     bool td (te.first && te.second == entry_type::directory);
 
@@ -513,7 +506,7 @@ namespace butl
     // either directories or not directories.
     //
     if (fe.first && te.first && fd != td)
-      throw system_error (EIO, system_category (), "not a directory");
+      throw_generic_error (ENOTDIR);
 
     DWORD mfl (fd ? 0 : (MOVEFILE_COPY_ALLOWED | MOVEFILE_REPLACE_EXISTING));
 
@@ -534,15 +527,7 @@ namespace butl
 	MoveFileExA (f, t, mfl))
       return;
 
-    // @@ The exception description will look like:
-    //
-    //    file not found. : Access denied
-    //
-    //    Probably need to consider such discriptions for sanitizing in
-    //    operator<<(ostream,exception).
-    //
-    string e (win32::error_msg (ec));
-    throw system_error (EIO, system_category (), e);
+    throw_system_error (ec);
 
 #endif
   }
@@ -561,7 +546,7 @@ namespace butl
       if (errno == ENOENT || errno == ENOTDIR)
         return timestamp_nonexistent;
       else
-        throw system_error (errno, system_category ());
+        throw_generic_error (errno);
     }
 
     return S_ISREG (s.st_mode)
@@ -581,7 +566,7 @@ namespace butl
     struct _stat s;
     if (_stat (p.string ().c_str (), &s) != 0)
 #endif
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 
     // VC++ has no S_IRWXU defined. MINGW GCC <= 4.9 has no S_IRWXG, S_IRWXO
     // defined.
@@ -624,7 +609,7 @@ namespace butl
 #else
     if (_chmod (p.string ().c_str (), m) == -1)
 #endif
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
   }
 
   // dir_{entry,iterator}
@@ -648,7 +633,7 @@ namespace butl
       e_ = move (x.e_);
 
       if (h_ != nullptr && closedir (h_) == -1)
-        throw system_error (errno, system_category ());
+        throw_generic_error (errno);
 
       h_ = x.h_;
       x.h_ = nullptr;
@@ -665,7 +650,7 @@ namespace butl
          ? stat (p.string ().c_str (), &s)
          : lstat (p.string ().c_str (), &s)) != 0)
     {
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
     }
 
     entry_type r;
@@ -696,7 +681,7 @@ namespace butl
     h_ = h.get ();
 
     if (h_ == nullptr)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 
     next ();
 
@@ -771,7 +756,7 @@ namespace butl
         h_ = nullptr;
       }
       else
-        throw system_error (errno, system_category ());
+        throw_generic_error (errno);
 
       break;
     }
@@ -796,7 +781,7 @@ namespace butl
       e_ = move (x.e_);
 
       if (h_ != -1 && _findclose (h_) == -1)
-        throw system_error (errno, system_category ());
+        throw_generic_error (errno);
 
       h_ = x.h_;
       x.h_ = -1;
@@ -814,7 +799,7 @@ namespace butl
 
     struct _stat s;
     if (_stat (p.string ().c_str (), &s) != 0)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 
     entry_type r;
     if (S_ISREG (s.st_mode))
@@ -876,7 +861,7 @@ namespace butl
         // Check to distinguish non-existent vs empty directories.
         //
         if (!dir_exists (e_.b_))
-          throw system_error (ENOENT, system_category ());
+          throw_generic_error (ENOENT);
 
         h_ = _findfirst ((e_.b_ / path ("*")).string ().c_str (), &fi);
         r = h_ != -1;
@@ -917,7 +902,7 @@ namespace butl
         }
       }
       else
-        throw system_error (errno, system_category ());
+        throw_generic_error (errno);
 
       break;
     }
@@ -1187,6 +1172,10 @@ namespace butl
         // other error. We consider ENOTDIR as a variety of removal, with a
         // new filesystem entry being created afterwards.
         //
+        // Make sure that the error denotes errno portable code.
+        //
+        assert (e.code ().category () == generic_category ());
+
         int ec (e.code ().value ());
         if (ec != ENOENT && ec != ENOTDIR)
           throw;
diff --git a/butl/pager.cxx b/butl/pager.cxx
index e327960..fe59e5b 100644
--- a/butl/pager.cxx
+++ b/butl/pager.cxx
@@ -16,9 +16,9 @@
 
 #include <cstring>      // strchr()
 #include <utility>      // move()
-#include <system_error>
 
-#include <butl/utility>  // operator<<(ostream, exception)
+#include <butl/utility>  // operator<<(ostream, exception),
+                         // throw_generic_error()
 #include <butl/fdstream> // fdclose()
 
 using namespace std;
@@ -139,7 +139,7 @@ namespace butl
         p_.out_fd.reset ();
 
         if (pager != nullptr)
-          throw system_error (ECHILD, system_category ());
+          throw_generic_error (ECHILD);
       }
       else
         os_.open (move (p_.out_fd));
diff --git a/butl/path.cxx b/butl/path.cxx
index 9947bbe..dfa812b 100644
--- a/butl/path.cxx
+++ b/butl/path.cxx
@@ -28,10 +28,10 @@
 #include <atomic>
 #include <cassert>
 #include <cstring> // strcpy()
-#include <system_error>
 
 #include <butl/export>
 
+#include <butl/utility> // throw_*_error()
 #include <butl/process>
 
 #ifndef _WIN32
@@ -65,12 +65,12 @@ namespace butl
 #ifdef _WIN32
     char cwd[_MAX_PATH];
     if (_getcwd (cwd, _MAX_PATH) == 0)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
     cwd[0] = toupper (cwd[0]); // Canonicalize.
 #else
     char cwd[PATH_MAX];
     if (getcwd (cwd, PATH_MAX) == 0)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 #endif
 
     return cwd;
@@ -93,10 +93,10 @@ namespace butl
                           : string_type (s + directory_separator));
 
     if (_chdir (d.c_str ()) != 0)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 #else
     if (chdir (s.c_str ()) != 0)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 #endif
   }
 
@@ -115,10 +115,10 @@ namespace butl
 
     struct stat s;
     if (stat (dir, &s) != 0)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 
     if (!S_ISDIR (s.st_mode))
-      throw system_error (ENOTDIR, system_category ());
+      throw_generic_error (ENOTDIR);
 
     return dir;
   }
@@ -141,13 +141,13 @@ namespace butl
 
     int r (getpwuid_r (getuid (), &pw, buf, sizeof (buf), &rpw));
     if (r == -1)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 
     if (r == 0 && rpw == nullptr)
       // According to POSIX errno should be left unchanged if an entry is not
       // found.
       //
-      throw system_error (ENOENT, system_category ());
+      throw_generic_error (ENOENT);
 
     return pw.pw_dir;
   }
@@ -160,10 +160,7 @@ namespace butl
 #ifdef _WIN32
     char d[_MAX_PATH + 1];
     if (GetTempPathA (_MAX_PATH + 1, d) == 0)
-    {
-      string e (last_error_msg ());
-      throw system_error (ENOTDIR, system_category (), e);
-    }
+      throw_system_error (GetLastError ());
 
     return d;
 #else
@@ -198,10 +195,7 @@ namespace butl
     HRESULT r (SHGetFolderPathA (NULL, CSIDL_PROFILE, NULL, 0, h));
 
     if (!SUCCEEDED (r))
-    {
-      string e (error_msg (r));
-      throw system_error (ENOTDIR, system_category (), e);
-    }
+      throw_system_error (r);
 
     return h;
 #endif
@@ -221,7 +215,7 @@ namespace butl
       if (errno == EACCES || errno == ENOENT || errno == ENOTDIR)
         throw invalid_basic_path<char> (s);
       else
-        throw system_error (errno, system_category ());
+        throw_generic_error (errno);
     }
 
     s = r;
@@ -239,16 +233,16 @@ namespace butl
 #ifdef _WIN32
     wchar_t wcwd[_MAX_PATH];
     if (_wgetcwd (wcwd, _MAX_PATH) == 0)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
     wcwd[0] = toupper (wcwd[0]); // Canonicalize.
 #else
     char cwd[PATH_MAX];
     if (getcwd (cwd, PATH_MAX) == 0)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 
     wchar_t wcwd[PATH_MAX];
     if (mbstowcs (wcwd, cwd, PATH_MAX) == size_type (-1))
-      throw system_error (EINVAL, system_category ());
+      throw_generic_error (EINVAL);
 #endif
 
     return wcwd;
@@ -268,17 +262,17 @@ namespace butl
                           : string_type (s + directory_separator));
 
     if (_wchdir (d.c_str ()) != 0)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 #else
     char ns[PATH_MAX + 1];
 
     if (wcstombs (ns, s.c_str (), PATH_MAX) == size_type (-1))
-      throw system_error (EINVAL, system_category ());
+      throw_generic_error (EINVAL);
 
     ns[PATH_MAX] = '\0';
 
     if (chdir (ns) != 0)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 #endif
   }
 
@@ -289,10 +283,7 @@ namespace butl
 #ifdef _WIN32
     wchar_t d[_MAX_PATH + 1];
     if (GetTempPathW (_MAX_PATH + 1, d) == 0)
-    {
-      string e (last_error_msg ());
-      throw system_error (ENOTDIR, system_category (), e);
-    }
+      throw_system_error (GetLastError ());
 #else
     wchar_t d[PATH_MAX];
 
@@ -304,10 +295,10 @@ namespace butl
     size_t r (mbstowcs (d, butl::temp_directory (), PATH_MAX));
 
     if (r == size_t (-1))
-      throw system_error (EINVAL, system_category ());
+      throw_generic_error (EINVAL);
 
     if (r == PATH_MAX)
-      throw system_error (ENOTSUP, system_category ());
+      throw_generic_error (ENOTSUP);
 #endif
 
     return d;
@@ -331,10 +322,10 @@ namespace butl
     size_t r (mbstowcs (d, home ().c_str (), PATH_MAX));
 
     if (r == size_t (-1))
-      throw system_error (EINVAL, system_category ());
+      throw_generic_error (EINVAL);
 
     if (r == PATH_MAX)
-      throw system_error (ENOTSUP, system_category ());
+      throw_generic_error (ENOTSUP);
 
     return d;
 #else
@@ -347,10 +338,7 @@ namespace butl
     HRESULT r (SHGetFolderPathW (NULL, CSIDL_PROFILE, NULL, 0, h));
 
     if (!SUCCEEDED (r))
-    {
-      string e (error_msg (r));
-      throw system_error (ENOTDIR, system_category (), e);
-    }
+      throw_system_error (r);
 
     return h;
 #endif
@@ -388,7 +376,7 @@ namespace butl
       return false;
 
     if (h == -1 || _findclose (h) == -1)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 
     r += fi.name;
     return true;
diff --git a/butl/process b/butl/process
index 19bea3a..31cb681 100644
--- a/butl/process
+++ b/butl/process
@@ -30,13 +30,14 @@ namespace butl
 
 #ifndef _WIN32
     process_error (int e, bool child)
-        : system_error (e, std::system_category ()), child_ (child) {}
+        : system_error (e, std::generic_category ()), child_ (child) {}
 #else
     process_error (int e, bool child = false)
-        : system_error (e, std::system_category ()), child_ (child) {}
+        : system_error (e, std::generic_category ()), child_ (child) {}
 
-    process_error (const std::string& d, int e = ECHILD)
-        : system_error (e, std::system_category (), d), child_ (false) {}
+    process_error (const std::string& d, int fallback_errno_code = 0)
+        : system_error (fallback_errno_code, std::system_category (), d),
+          child_ (false) {}
 #endif
 
   private:
diff --git a/butl/timestamp.cxx b/butl/timestamp.cxx
index d38c018..971f1ef 100644
--- a/butl/timestamp.cxx
+++ b/butl/timestamp.cxx
@@ -15,7 +15,8 @@
 #include <ostream>
 #include <utility>      // pair, make_pair()
 #include <stdexcept>    // runtime_error
-#include <system_error>
+
+#include <butl/utility> // throw_generic_error()
 
 using namespace std;
 
@@ -137,7 +138,7 @@ namespace butl
     if ((local
          ? details::localtime (&t, &tm)
          : details::gmtime (&t, &tm)) == nullptr)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 
     using namespace chrono;
 
@@ -147,7 +148,7 @@ namespace butl
     char fmt[256];
     size_t n (strlen (format));
     if (n + 1 > sizeof (fmt))
-      throw system_error (EINVAL, system_category ());
+      throw_generic_error (EINVAL);
     memcpy (fmt, format, n + 1);
 
     // Chunk the format string into fragments that we feed to put_time() and
@@ -175,18 +176,18 @@ namespace butl
 
           j += 2; // Character after '['.
           if (j == n)
-            throw system_error (EINVAL, system_category ());
+            throw_generic_error (EINVAL);
 
           char d ('\0');
           if (fmt[j] != 'N')
           {
             d = fmt[j];
             if (++j == n || fmt[j] != 'N')
-              throw system_error (EINVAL, system_category ());
+              throw_generic_error (EINVAL);
           }
 
           if (++j == n || fmt[j] != ']')
-            throw system_error (EINVAL, system_category ());
+            throw_generic_error (EINVAL);
 
           if (ns != nanoseconds::zero ())
           {
@@ -267,7 +268,7 @@ namespace butl
     {
       std::tm tm;
       if (details::gmtime (&t, &tm) == nullptr)
-        throw system_error (errno, system_category ());
+        throw_generic_error (errno);
 
       if (t >= 24 * 60 * 60)
         tm.tm_mday -= 1; // Make day of the month to be a zero-based number.
@@ -431,7 +432,7 @@ namespace butl
   static pair<tm, chrono::nanoseconds>
   from_string (const char* input, const char* format, const char** end)
   {
-    auto bad_val = []() {throw system_error (EINVAL, system_category ());};
+    auto bad_val = [] () {throw_generic_error (EINVAL);};
 
     // See if we have our specifier.
     //
@@ -603,7 +604,7 @@ namespace butl
 
     time_t time (local ? mktime (&t.first) : timegm (&t.first));
     if (time == -1)
-      throw system_error (errno, system_category ());
+      throw_generic_error (errno);
 
     return timestamp::clock::from_time_t (time) +
       chrono::duration_cast<duration> (t.second);
diff --git a/butl/utility b/butl/utility
index 7dc4d73..673b715 100644
--- a/butl/utility
+++ b/butl/utility
@@ -30,10 +30,10 @@ namespace butl
   //
   // See also the exception sanitization below.
   //
-  [[noreturn]] void
-  throw_generic_error (int errno_code);
+  [[noreturn]] LIBBUTL_EXPORT void
+  throw_generic_error (int errno_code, const char* what = nullptr);
 
-  [[noreturn]] void
+  [[noreturn]] LIBBUTL_EXPORT void
   throw_system_error (int system_code, int fallback_errno_code = 0);
 
   // Convert ASCII character/string case. If there is no upper/lower case
@@ -252,6 +252,7 @@ namespace std
   //
   // - stripping leading colons and spaces (see fdstream.cxx)
   // - stripping trailing newlines, periods, and spaces
+  // - stripping system error redundant suffix (see utility.cxx)
   // - lower-case the first letter if the beginning looks like a word
   //
   LIBBUTL_EXPORT ostream&
diff --git a/butl/utility.cxx b/butl/utility.cxx
index 84c8a74..03045da 100644
--- a/butl/utility.cxx
+++ b/butl/utility.cxx
@@ -2,12 +2,20 @@
 // copyright : Copyright (c) 2014-2017 Code Synthesis Ltd
 // license   : MIT; see accompanying LICENSE file
 
-#include <ostream>
-
 #include <butl/utility>
 
+#ifdef _WIN32
+#  include <butl/win32-utility>
+#endif
+
+#include <string>
+#include <ostream>
+#include <system_error>
+
 namespace butl
 {
+  using namespace std;
+
 #ifndef __cpp_lib_uncaught_exceptions
 
 #ifdef __cpp_thread_local
@@ -23,6 +31,39 @@ namespace butl
 #endif
 
 #endif
+
+  [[noreturn]] void
+  throw_generic_error (int errno_code, const char* what)
+  {
+    if (what == nullptr)
+      throw system_error (errno_code, generic_category ());
+    else
+      throw system_error (errno_code, generic_category (), what);
+  }
+
+  [[noreturn]] void
+#ifndef _WIN32
+  throw_system_error (int system_code, int)
+  {
+    throw system_error (system_code, system_category ());
+#else
+  throw_system_error (int system_code, int fallback_errno_code)
+  {
+    // Here we work around MinGW libstdc++ that interprets Windows system error
+    // codes (for example those returned by GetLastError()) as errno codes. The
+    // resulting system_error description will have the following form:
+    //
+    // <system_code description>: <fallback_errno_code description>
+    //
+    // Also note that the fallback-related description suffix is stripped by
+    // our custom operator<<(ostream, exception) for the common case (see
+    // below).
+    //
+    throw system_error (fallback_errno_code,
+                        system_category (),
+                        win32::error_msg (system_code));
+#endif
+  }
 }
 
 namespace std
@@ -63,6 +104,16 @@ namespace std
       break;
     }
 
+    // Strip the suffix for system_error thrown by
+    // throw_system_error(system_code) on Windows. For example for the
+    // ERROR_INVALID_DATA error code the original description will be
+    // 'Invalid data. : Success' for MinGW libstdc++ and
+    // 'Invalid data. : Success.' for msvcrt.
+    //
+    if (n >= 11 &&
+        string::traits_type::compare (s + n - 11, ". : Success", 11) == 0)
+      n -= 11;
+
     // Lower-case the first letter if the beginning looks like a word (the
     // second character is the lower-case letter or space).
     //