https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71504
Bug ID: 71504
Summary: bogus error: accessing value through a glvalue in a
constant expression
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
All recent versions of G++ fail to compile the following well-formed program
with the error below. Clang compiles it fine, as does EDG eccp 4.11 (though
eccp issues a bogus "subscript out of range" warning).
$ cat zzz.c && /home/msebor/build/gcc-trunk-svn/gcc/xgcc -B
/home/msebor/build/gcc-trunk-svn/gcc -Wall -Wextra -Wpedantic -fpermissive
-fdump-tree-gimple=/dev/stdout -xc++ zzz.c
typedef const char A4 [10];
constexpr A4 a [] = { "123", "123456", "123456789" };
constexpr int len (const char *s)
{
return *s ? 1 + len (s + 1) : 0;
}
constexpr const char *s = a [0];
constexpr const char *t = (a + 2)[-2];
constexpr int n0 = len (s);
constexpr int n1 = len (t);
constexpr int n2 = len (a [0]);
constexpr int n3 = len ((a + 2)[-2]);
#define A(e) static_assert ((e), #e)
A (n0 == 3);
A (n0 == n1);
A (n0 == n2);
A (n0 == n3);
zzz.c:14:24: in constexpr expansion of ‘len(((const char*)(& a)))’
zzz.c:14:26: error: accessing value of ‘a’ through a ‘const char’ glvalue in a
constant expression
constexpr int n1 = len (t);
^
zzz.c:17:24: in constexpr expansion of ‘len(((const char*)((const char
(*)[10])(& a))))’
zzz.c:17:36: error: accessing value of ‘a’ through a ‘const char’ glvalue in a
constant expression
constexpr int n3 = len ((a + 2)[-2]);
^
