libstdc++: Add pretty printer for std::error_code and std::error_condition

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	* python/libstdcxx/v6/printers.py (StdErrorCodePrinter): Define.
	(build_libstdcxx_dictionary): Register printer for
	std::error_code and std::error_condition.
	* testsuite/libstdc++-prettyprinters/cxx11.cc: Test it.

libstdc++-v3/python/libstdcxx/v6/printers.py

@@ -18,7 +18,7 @@
 import gdb
 import itertools
 import re
-import sys
+import sys, os, errno
 
 ### Python 2 + Python 3 compatibility code
 
@@ -1484,6 +1484,57 @@ class StdCmpCatPrinter:
             name = names[int(self.val)]
         return 'std::{}::{}'.format(self.typename, name)
 
+class StdErrorCatPrinter:
+    "Print an object derived from std::error_category"
+
+    def __init__ (self, typename, val):
+        self.val = val
+        self.typename = typename
+
+    def to_string (self):
+        gdb.set_convenience_variable('__cat', self.val)
+        name = gdb.parse_and_eval('$__cat->name()').string()
+        return 'error category = "{}"'.format(name)
+
+class StdErrorCodePrinter:
+    "Print a std::error_code or std::error_condition"
+
+    _errno_categories = None # List of categories that use errno values
+
+    def __init__ (self, typename, val):
+        self.val = val
+        self.typename = typename
+        # Do this only once ...
+        if StdErrorCodePrinter._errno_categories is None:
+            StdErrorCodePrinter._errno_categories = ['generic']
+            try:
+                import posix
+                StdErrorCodePrinter._errno_categories.append('system')
+            except ImportError:
+                pass
+
+    @staticmethod
+    def _category_name(cat):
+        "Call the virtual function that overrides std::error_category::name()"
+        gdb.set_convenience_variable('__cat', cat)
+        return gdb.parse_and_eval('$__cat->name()').string()
+
+    def to_string (self):
+        value = self.val['_M_value']
+        category = self._category_name(self.val['_M_cat'])
+        strval = str(value)
+        if value == 0:
+            default_cats = {'error_code':'system', 'error_condition':'generic'}
+            unqualified = self.typename.split('::')[-1]
+            if category == default_cats[unqualified]:
+                return self.typename + ' = { }' # default-constructed value
+        if value > 0 and category in StdErrorCodePrinter._errno_categories:
+            try:
+                strval = errno.errorcode[int(value)]
+            except:
+                pass
+        return '%s = {"%s": %s}' % (self.typename, category, strval)
+
 # A "regular expression" printer which conforms to the
 # "SubPrettyPrinter" protocol from gdb.printing.
 class RxPrinter(object):
@@ -1886,6 +1937,8 @@ def build_libstdcxx_dictionary ():
     libstdcxx_printer.add_version('std::__cxx11::', 'basic_string', StdStringPrinter)
     libstdcxx_printer.add_container('std::', 'bitset', StdBitsetPrinter)
     libstdcxx_printer.add_container('std::', 'deque', StdDequePrinter)
+    libstdcxx_printer.add_version('std::', 'error_code', StdErrorCodePrinter)
+    libstdcxx_printer.add_version('std::', 'error_condition', StdErrorCodePrinter)
     libstdcxx_printer.add_container('std::', 'list', StdListPrinter)
     libstdcxx_printer.add_container('std::__cxx11::', 'list', StdListPrinter)
     libstdcxx_printer.add_container('std::', 'map', StdMapPrinter)

libstdc++-v3/testsuite/libstdc++-prettyprinters/cxx11.cc

@@ -155,6 +155,25 @@ main()
 // { dg-final { note-test tpl {std::tuple containing = {[1] = 6, [2] = 7}} } }
   ExTuple &rtpl = tpl;
 // { dg-final { note-test rtpl {std::tuple containing = {[1] = 6, [2] = 7}} } }
+
+  std::error_code e0;
+  // { dg-final { note-test e0 {std::error_code = { }} } }
+  std::error_condition ec0;
+  // { dg-final { note-test ec0 {std::error_condition = { }} } }
+  std::error_code einval = std::make_error_code(std::errc::invalid_argument);
+  // { dg-final { note-test einval {std::error_code = {"generic": EINVAL}} } }
+  std::error_condition ecinval = std::make_error_condition(std::errc::invalid_argument);
+  // { dg-final { note-test ecinval {std::error_condition = {"generic": EINVAL}} } }
+
+  struct custom_cat : std::error_category {
+    const char* name() const noexcept { return "miaow"; }
+    std::string message(int) const { return ""; }
+  } cat;
+  std::error_code emiaow(42, cat);
+  // { dg-final { note-test emiaow {std::error_code = {"miaow": 42}} } }
+  std::error_condition ecmiaow(42, cat);
+  // { dg-final { note-test ecmiaow {std::error_condition = {"miaow": 42}} } }
+
   placeholder(""); // Mark SPOT
   use(efl);
   use(fl);