[gcc r10-10189] libstdc++: Add pretty printer for std::error_code and std::error_condition

[gcc r10-10189] libstdc++: Add pretty printer for std::error_code and std::error_condition

[Jonathan Wakely]

https://gcc.gnu.org/g:58d2ce4d496f4021e85431f0e958757414309764

commit r10-10189-g58d2ce4d496f4021e85431f0e958757414309764
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Aug 16 17:41:50 2021 +0100

    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.
    
    (cherry picked from commit 2db38d9fcacf522fe9b98ba847e79ba33abdcadc)

Diff:
---
 libstdc++-v3/python/libstdcxx/v6/printers.py       | 43 +++++++++++++++++++++-
 .../testsuite/libstdc++-prettyprinters/cxx11.cc    | 19 ++++++++++
 2 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/python/libstdcxx/v6/printers.py b/libstdc++-v3/python/libstdcxx/v6/printers.py
index 01f3bf6c6a4..52abcdedb2e 100644
--- a/libstdc++-v3/python/libstdcxx/v6/printers.py
+++ b/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
 
@@ -1465,6 +1465,45 @@ class StdCmpCatPrinter:
             name = names[int(self.val)]
         return 'std::{}::{}'.format(self.typename, 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):
@@ -1867,6 +1906,8 @@ 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)
diff --git a/libstdc++-v3/testsuite/libstdc++-prettyprinters/cxx11.cc b/libstdc++-v3/testsuite/libstdc++-prettyprinters/cxx11.cc
index 001b121dcec..d66df64285f 100644
--- a/libstdc++-v3/testsuite/libstdc++-prettyprinters/cxx11.cc
+++ b/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);