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c: restore definition of _Noreturn as [[noreturn]] in C++

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c.m4 contains a definition of _Noreturn which is modeled after
gnulib's lib/_Noreturn.h.  The latter was recently
changed (b61bf2f0e8) to not using
[[noreturn]] at all, because the uses of _Noreturn in gnulib are
sometimes incompatible with the rules of [[noreturn]].

As a result glr.cc started to use _Noreturn in C++, which clang
refuses (all the glr.cc tests currently fail with Clang++).

* data/skeletons/c.m4 (b4_attribute_define): Restore the definition of
_Noreturn as [[noreturn]] in modern C++.
The generated code uses _Noreturn in places where [[noreturn]] is
valid.
This commit is contained in:
Akim Demaille
2020-05-16 17:24:31 +02:00
parent 4619b32dc0
commit 22c3839168
1 changed files with 6 additions and 9 deletions
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15
data/skeletons/c.m4
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@@ -355,18 +355,15 @@ m4_define([b4_attribute_define],
#endif
]m4_bmatch([$1], [\bnoreturn\b], [[/* The _Noreturn keyword of C11. */
]dnl This is an exact copy of lib/_Noreturn.h.
]dnl This is close to lib/_Noreturn.h, except that we do enable
dnl the use of [[noreturn]], because _Noreturn is used in places
dnl where [[noreturn]] works in C++. We need this in particular
dnl because of glr.cc which compiles code from glr.c in C++.
dnl And the C++ compiler chokes on _Noreturn.
[#ifndef _Noreturn
# if (defined __cplusplus \
&& ((201103 <= __cplusplus && !(__GNUC__ == 4 && __GNUC_MINOR__ == 7)) \
|| (defined _MSC_VER && 1900 <= _MSC_VER)) \
&& 0)
/* [[noreturn]] is not practically usable, because with it the syntax
extern _Noreturn void func (...);
would not be valid; such a declaration would only be valid with 'extern'
and '_Noreturn' swapped, or without the 'extern' keyword. However, some
AIX system header files and several gnulib header files use precisely
this syntax with 'extern'. */
|| (defined _MSC_VER && 1900 <= _MSC_VER)))
# define _Noreturn [[noreturn]]
# elif ((!defined __cplusplus || defined __clang__) \
&& (201112 <= (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0) \