[libcxx-commits] [libcxx] 049f6c2 - [libc++] Resolve missing table_size symbol

Muiez Ahmed via libcxx-commits libcxx-commits at lists.llvm.org
Thu Nov 18 12:51:58 PST 2021 

Author: Muiez Ahmed
Date: 2021-11-18T15:49:45-05:00
New Revision: 049f6c29a6f0a91263588d470c1b09dccd4c70d4

URL: https://github.com/llvm/llvm-project/commit/049f6c29a6f0a91263588d470c1b09dccd4c70d4
DIFF: https://github.com/llvm/llvm-project/commit/049f6c29a6f0a91263588d470c1b09dccd4c70d4.diff

LOG: [libc++] Resolve missing table_size symbol

The aim of this patch is to resolve the missing `table_size` symbol (see reduced test case). That const variable is declared and defined in //libcxx/include/locale//; however, the test case suggests that the symbol is missing. This is due to a C++ pitfall (highlighted [[ https://quuxplusone.github.io/blog/2020/09/19/value-or-pitfall/ | here ]]). In summary, assigning the reference of `table_size` doesn't enforce the const-ness and expects to find `table_size` in the DLL. The fix is to use `constexpr` or have an out-of-line definition in the src (for consistency).

Differential Revision: https://reviews.llvm.org/D110647

Added: 
    libcxx/test/std/localization/locale.categories/category.ctype/facet.ctype.special/facet.ctype.char.statics/table_size.pass.cpp

Modified: 
    libcxx/lib/abi/CHANGELOG.TXT
    libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist
    libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist
    libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist
    libcxx/src/locale.cpp

Removed: 
    


################################################################################
diff  --git a/libcxx/lib/abi/CHANGELOG.TXT b/libcxx/lib/abi/CHANGELOG.TXT
index 58cbf9aef038..f85738ede01d 100644
--- a/libcxx/lib/abi/CHANGELOG.TXT
+++ b/libcxx/lib/abi/CHANGELOG.TXT
@@ -16,6 +16,21 @@ New entries should be added directly below the "Version" header.
 Version 14.0
 ------------
 
+* [libc++] Resolve missing table_size symbol
+
+  This commit added an out-of-line definition for `table_size` in the library.
+  This is not an ABI break since we are just adding a symbol to the library.
+  In fact, any program that would have attempted to refer to that symbol would
+  have previously failed to link.
+
+  x86_64-apple-apple-darwin
+  -------------------------
+  Symbol added: _ZNSt3__15ctypeIcE10table_sizeE
+
+  x86_64-unknown-linux-gnu
+  ------------------------
+  Symbol added: _ZNSt3__15ctypeIcE10table_sizeE
+
 * [libc++] Always define a key function for std::bad_function_call in the dylib
 
   This commit added a new explicit instantiation of std::bad_function_call's

diff  --git a/libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist b/libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist
index f037b1bc27de..4c6661d38ae5 100644
--- a/libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist
+++ b/libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist
@@ -1646,6 +1646,7 @@
 {'is_defined': True, 'name': '__ZNSt3__14stolERKNS_12basic_stringIwNS_11char_traitsIwEENS_9allocatorIwEEEEPmi', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__14wcinE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__15alignEmmRPvRm', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__15ctypeIcE10table_sizeE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__15ctypeIcE13classic_tableEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__15ctypeIcE2idE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__15ctypeIcEC1EPKjbm', 'type': 'FUNC'}

diff  --git a/libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist b/libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist
index 2318cb41b77a..178e46ed6660 100644
--- a/libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist
+++ b/libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist
@@ -1646,6 +1646,7 @@
 {'is_defined': True, 'name': '__ZNSt3__14stolERKNS_12basic_stringIwNS_11char_traitsIwEENS_9allocatorIwEEEEPmi', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__14wcinE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__15alignEmmRPvRm', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__15ctypeIcE10table_sizeE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__15ctypeIcE13classic_tableEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__15ctypeIcE2idE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__15ctypeIcEC1EPKjbm', 'type': 'FUNC'}

diff  --git a/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist b/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist
index c815c446df1b..36f101ad4d75 100644
--- a/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist
+++ b/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist
@@ -1337,6 +1337,7 @@
 {'is_defined': True, 'name': '_ZNSt3__14stolERKNS_12basic_stringIwNS_11char_traitsIwEENS_9allocatorIwEEEEPmi', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__14wcinE', 'size': 168, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZNSt3__15alignEmmRPvRm', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__15ctypeIcE10table_sizeE', 'size': 8, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZNSt3__15ctypeIcE13classic_tableEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__15ctypeIcE21__classic_lower_tableEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__15ctypeIcE21__classic_upper_tableEv', 'type': 'FUNC'}

diff  --git a/libcxx/src/locale.cpp b/libcxx/src/locale.cpp
index 289523708163..79f03b85fab3 100644
--- a/libcxx/src/locale.cpp
+++ b/libcxx/src/locale.cpp
@@ -988,6 +988,8 @@ ctype<wchar_t>::do_narrow(const char_type* low, const char_type* high, char dfau
 
 locale::id ctype<char>::id;
 
+const size_t ctype<char>::table_size;
+
 ctype<char>::ctype(const mask* tab, bool del, size_t refs)
     : locale::facet(refs),
       __tab_(tab),

diff  --git a/libcxx/test/std/localization/locale.categories/category.ctype/facet.ctype.special/facet.ctype.char.statics/table_size.pass.cpp b/libcxx/test/std/localization/locale.categories/category.ctype/facet.ctype.special/facet.ctype.char.statics/table_size.pass.cpp
new file mode 100644
index 000000000000..576177591e88
--- /dev/null
+++ b/libcxx/test/std/localization/locale.categories/category.ctype/facet.ctype.special/facet.ctype.char.statics/table_size.pass.cpp
@@ -0,0 +1,31 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <locale>
+
+// template <> class ctype<char>
+
+// Make sure we can reference std::ctype<char>::table_size.
+
+// Before https://llvm.org/D110647, the shared library did not contain
+// std::ctype<char>::table_size, so this test fails with a link error.
+// XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx10.{{9|10|11|12|13|14|15}}
+// XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx{{11|12|13}}
+
+#include <locale>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main(int, char**) {
+  typedef std::ctype<char> F;
+  const size_t* G = &F::table_size;
+  assert(*G >= 256);
+
+  return 0;
+}

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