g++.dg/warn/Wstringop-overflow-6.C tests for a bogus overflow warning in
system headers. This testcase was generating a -Wchar-subscript warning
on AIX because ctype_inline.h was subscripting AIX _OBJ_DATA using a char.
The _M_table case cast the subscript to unsigned char, but the _OBJ_DATA
case did not.
The investigation also exposed that AIX has added a thread-safe variant
of access to __lc_type that had not been applied to the libstdc++
implementation.
This patch casts the subscript to unsigned char and adds the THREAD_SAFE
variant. libstdc++ always is compiled with pthreads, but it is good
to make the situation explicit and to document the appropriate usage.
Bootstrapped on powerpc-ibm-aix7.2.3.0.
libstdc++-v3/ChangeLog:
* config/os/aix/ctype_inline.h (bool ctype<char>:: is): Cast
_OBJ_DATA subscript to unsigned char. Add _THREAD_SAFE access to
__lc_type.
(const char* ctype<char>:: is): Same.
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