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* [PATCH] print extended assertion failures to stderr
@ 2021-10-27  8:25 Jay Feldblum
  2021-11-04 11:30 ` Jonathan Wakely
  0 siblings, 1 reply; 7+ messages in thread
From: Jay Feldblum @ 2021-10-27  8:25 UTC (permalink / raw)
  To: libstdc++, gcc-patches

From: yfeldblum <yfeldblum@gmail.com>

The stdout stream is reserved for output intentionally produced by the
application. Assertion failures and other forms of logging must be
emitted to stderr, not to stdout.

It is common for testing and monitoring infrastructure to scan stderr
for errors, such as for assertion failures, and to collect or retain
them for analysis or observation. It is a norm that assertion failures
match this expectation in practice.

While `__builtin_fprintf` is available as a builtin, there is no
equivalent builtin for `stderr`. The only option in practice is to use
the macro `stderr`, which requires `#include <cstdio>`. It is desired
not to add such an include to `bits/c++config` so the solution is to
write and export a function which may be called by `bits/c++config`.

This is expected to be API-compatible and ABI-compatible with caveats.
Code compiled against an earlier libstdc++ will work when linked into a
later libstdc++ but the stream to which assertion failures are logged is
anybody's guess, and in practice will be determined by the link line and
the choice of linker. This fix targets builds for which all C++ code is
built against a libstdc++ with the fix.

Alternatives:
* This, which is the smallest change.
* This, but also defining symbols `std::__stdin` and `std::__stdout` for
  completeness.
* Define a symbol like `std::__printf_stderr` which prints any message
  with any formatting to stderr, just as `std::printf` does to stdout,
  and call that from `std::__replacement_assert` instead of calling
  `__builtin_printf`.
* Move `std::__replacement_assert` into libstdc++.so and no longer mark
  it as weak. This allows an application with some parts built against a
  previous libstdc++ to guarantee that the fix will be applied at least
  to the parts that are built against a libstdc++ containing the fix.

libstdc++-v3/ChangeLog:
include/bits/c++config (__glibcxx_assert): print to stderr.
---
 libstdc++-v3/include/bits/c++config |  8 ++++--
 libstdc++-v3/src/c++98/Makefile.am  |  1 +
 libstdc++-v3/src/c++98/Makefile.in  |  2 +-
 libstdc++-v3/src/c++98/stdio.cc     | 39 +++++++++++++++++++++++++++++
 4 files changed, 47 insertions(+), 3 deletions(-)
 create mode 100644 libstdc++-v3/src/c++98/stdio.cc

diff --git a/libstdc++-v3/include/bits/c++config
b/libstdc++-v3/include/bits/c++config
index a64958096718126a49e8767694e913ed96108df2..d821ba09d88dc3e42ff1807200cfece71cc18bd9
100644
--- a/libstdc++-v3/include/bits/c++config
+++ b/libstdc++-v3/include/bits/c++config
@@ -523,6 +523,10 @@ namespace std
 # ifdef _GLIBCXX_VERBOSE_ASSERT
 namespace std
 {
+  // Avoid the use of stderr, because we're trying to keep the <cstdio>
+  // include out of the mix.
+  extern "C++" void* __stderr() _GLIBCXX_NOEXCEPT;
+
   // Avoid the use of assert, because we're trying to keep the <cassert>
   // include out of the mix.
   extern "C++" _GLIBCXX_NORETURN
@@ -531,8 +535,8 @@ namespace std
         const char* __function, const char* __condition)
   _GLIBCXX_NOEXCEPT
   {
-    __builtin_printf("%s:%d: %s: Assertion '%s' failed.\n", __file, __line,
-      __function, __condition);
+    __builtin_fprintf(__stderr(), "%s:%d: %s: Assertion '%s' failed.\n",
+                      __file, __line, __function, __condition);
     __builtin_abort();
   }
 }
diff --git a/libstdc++-v3/src/c++98/Makefile.am
b/libstdc++-v3/src/c++98/Makefile.am
index b48b57a2945780bb48496d3b5e76de4be61f836e..4032f914ea20344f51f2f219c5575d2a3858c44c
100644
--- a/libstdc++-v3/src/c++98/Makefile.am
+++ b/libstdc++-v3/src/c++98/Makefile.am
@@ -136,6 +136,7 @@ sources = \
  math_stubs_float.cc \
  math_stubs_long_double.cc \
  stdexcept.cc \
+ stdio.cc \
  strstream.cc \
  tree.cc \
  istream.cc \
diff --git a/libstdc++-v3/src/c++98/Makefile.in
b/libstdc++-v3/src/c++98/Makefile.in
index f9ebb0ff4f4cb86cde7070b5ba6b8bf6a20515b3..e8aeb37d864a0ab7711d763fe8fbd3045db6e00d
100644
--- a/libstdc++-v3/src/c++98/Makefile.in
+++ b/libstdc++-v3/src/c++98/Makefile.in
@@ -142,7 +142,7 @@ am__objects_7 = bitmap_allocator.lo
pool_allocator.lo mt_allocator.lo \
  list.lo list-aux.lo list-aux-2.lo list_associated.lo \
  list_associated-2.lo locale.lo locale_init.lo locale_facets.lo \
  localename.lo math_stubs_float.lo math_stubs_long_double.lo \
- stdexcept.lo strstream.lo tree.lo istream.lo istream-string.lo \
+ stdexcept.lo stdio.lo strstream.lo tree.lo istream.lo istream-string.lo \
  streambuf.lo valarray.lo $(am__objects_1) $(am__objects_3) \
  $(am__objects_6)
 am_libc__98convenience_la_OBJECTS = $(am__objects_7)
diff --git a/libstdc++-v3/src/c++98/stdio.cc b/libstdc++-v3/src/c++98/stdio.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d0acb9117e1728f66f1a72ae3a9f471af72034ef
--- /dev/null
+++ b/libstdc++-v3/src/c++98/stdio.cc
@@ -0,0 +1,39 @@
+// Portability symbols for <cstdio> -*- C++ -*-
+
+// Copyright (C) 2021-2021 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+// <http://www.gnu.org/licenses/>.
+
+#include <bits/c++config.h>
+#include <cstdio>
+
+namespace std {
+
+// The name stderr is specified to be a macro and is specified to be defined in
+// C++ header cstdio or, equivalently, C header stdio.h. That means
it cannot be
+// used by code which intentionally avoids library includes, in particular, by
+// bits/c++config. And it cannot be declared or even aliased in such headers
+// since that would not be portable across libc implementations.
+extern "C++" void* __stderr() _GLIBCXX_NOEXCEPT {
+  return stderr;
+}
+
+}
-- 
2.30.2

^ permalink raw reply	[flat|nested] 7+ messages in thread
* [PATCH] print extended assertion failures to stderr
@ 2021-11-04 13:53 sotrdg sotrdg
  2021-11-04 13:54 ` Jonathan Wakely
  0 siblings, 1 reply; 7+ messages in thread
From: sotrdg sotrdg @ 2021-11-04 13:53 UTC (permalink / raw)
  To: unlvsur unlvsur via Libstdc++

I think We better put entire function

__replacement_assert

into other translation unit Instead of putting stderr?

Get Outlook for Android<https://aka.ms/AAb9ysg>

^ permalink raw reply	[flat|nested] 7+ messages in thread
end of thread, other threads:[~2021-11-04 23:44 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
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2021-10-27  8:25 [PATCH] print extended assertion failures to stderr Jay Feldblum
2021-11-04 11:30 ` Jonathan Wakely
2021-11-04 23:44   ` Jonathan Wakely
2021-11-04 13:53 sotrdg sotrdg
2021-11-04 13:54 ` Jonathan Wakely
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2021-11-04 14:17       ` sotrdg sotrdg
2021-11-04 15:13         ` Jonathan Wakely

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