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authorPedro Alves <pedro@palves.net>2020-09-29 20:08:51 +0100
committerPedro Alves <pedro@palves.net>2020-09-29 23:48:04 +0100
commitde38d64ad2502312afb0000ac806474c1e2c0fe5 (patch)
tree7f0eaefadcc4b0d8bbcc780f30917cfe597efbf6 /gdbsupport
parentaeaccbf4c55033bd6641709f98f3f6d65e695f85 (diff)
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Tweak gdbsupport/valid-expr.h for GCC 6, fix build
With GCC 6.4 and 6.5 (at least), unit tests that use gdbsupport/valid-expr.h's CHECK_VALID fail to compile, with: In file included from src/gdb/unittests/offset-type-selftests.c:24:0: src/gdb/unittests/offset-type-selftests.c: In substitution of 'template<class Expected, template<class ...> class Op, class ... Args> using is_detected_exact = std::is_same<Expected, typename gdb::detection_detail::detector<gdb::nonesuch, void, Op, Args ...>::type> [with Expected = selftests::offset_type::off_A&; Op = selftests::offset_type::check_valid_expr75::archetype; Args = {selftests::offset_type::off_A, selftests::offset_type::off_B}]': src/gdb/unittests/offset-type-selftests.c:75:1: required from here src/gdb/../gdbsupport/valid-expr.h:65:20: error: type/value mismatch at argument 2 in template parameter list for 'template<class Expected, template<class ...> class Op, class ... Args> using is_detected_exact = std::is_same<Expected, typename gdb::detection_detail::detector<gdb::nonesuch, void, Op, Args ...>::type>' archetype, TYPES>::value == VALID, \ ^ The important part is the "error: type/value mismatch" error. Seems like that GCC doesn't understand that archetype is an alias template, and is being strict in requiring a template class. The fix here is then to make archetype a template class, to pacify GCC. The resulting code looks like this: template <TYPENAMES, typename = decltype (EXPR)> struct archetype { }; static_assert (gdb::is_detected_exact<archetype<TYPES, EXPR_TYPE>, archetype, TYPES>::value == VALID, ""); is_detected_exact<Expected, Op, Args> checks whether Op<Args> is type Expected: - For Expected, we pass the explicit EXPR_TYPE, overriding the default parameter type of archetype. - For Args we don't pass the last template parameter, so archtype defaults to the EXPR's decltype. So in essence, we're really checking whether EXPR_TYPE is the same as decltype(EXPR). We need to do the decltype in a template context in order to trigger SFINAE instead of failing to compile. The hunk in unittests/enum-flags-selftests.c becomes necessary, because unlike with the current alias template version, this new version makes GCC trigger -Wenum-compare warnings as well: src/gdb/unittests/enum-flags-selftests.c:328:33: error: comparison between 'enum selftests::enum_flags_tests::RE' and 'enum selftests::enum_flags_tests::RE2' [-Werror=enum-compare] CHECK_VALID (true, bool, RE () != RE2 ()) ^ src/gdb/../gdbsupport/valid-expr.h:61:45: note: in definition of macro 'CHECK_VALID_EXPR_INT' template <TYPENAMES, typename = decltype (EXPR)> \ ^ Build-tested with: - GCC {4.8.5, 6.4, 6.5, 7.3.1, 9.3.0, 11.0.0-20200910} - Clang 10.0.0 gdbsupport/ChangeLog: * valid-expr.h (CHECK_VALID_EXPR_INT): Make archetype a template class instead of an alias template and adjust static_assert. gdb/ChangeLog: * unittests/enum-flags-selftests.c: Check whether __GNUC__ is defined before using '#pragma GCC diagnostic' instead of checking __clang__.
Diffstat (limited to 'gdbsupport')
-rw-r--r--gdbsupport/ChangeLog5
-rw-r--r--gdbsupport/valid-expr.h8
2 files changed, 10 insertions, 3 deletions
diff --git a/gdbsupport/ChangeLog b/gdbsupport/ChangeLog
index a2f563c..91435ff 100644
--- a/gdbsupport/ChangeLog
+++ b/gdbsupport/ChangeLog
@@ -1,3 +1,8 @@
+2020-09-29 Pedro Alves <pedro@palves.net>
+
+ * valid-expr.h (CHECK_VALID_EXPR_INT): Make archetype a template
+ class instead of an alias template and adjust static_assert.
+
2020-09-24 Simon Marchi <simon.marchi@efficios.com>
* event-loop.c (struct file_handler): Remove typedef, re-format.
diff --git a/gdbsupport/valid-expr.h b/gdbsupport/valid-expr.h
index 459de17..ff5b8f5 100644
--- a/gdbsupport/valid-expr.h
+++ b/gdbsupport/valid-expr.h
@@ -58,10 +58,12 @@
#define CHECK_VALID_EXPR_INT(TYPENAMES, TYPES, VALID, EXPR_TYPE, EXPR) \
namespace CONCAT (check_valid_expr, __LINE__) { \
\
- template <TYPENAMES> \
- using archetype = decltype (EXPR); \
+ template <TYPENAMES, typename = decltype (EXPR)> \
+ struct archetype \
+ { \
+ }; \
\
- static_assert (gdb::is_detected_exact<EXPR_TYPE, \
+ static_assert (gdb::is_detected_exact<archetype<TYPES, EXPR_TYPE>, \
archetype, TYPES>::value == VALID, \
""); \
} /* namespace */