https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68478
Bug ID: 68478
Summary: flexible array members have complete type
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
G++ accepts definitions of C flexible array members as an extension. However,
since C specifies that a flexible array member has an incomplete type, such a
member is not a valid operand in expressions that require an object to have a
complete type. An example is the sizeof expression. Since flexible array
members are provided for compatibility with C, they should be subject to the
same requirements and restrictions.
$ cat z.cpp && /build/gcc-trunk-svn/gcc/xgcc -B /build/gcc-trunk-svn/gcc -Wall
-Wextra -Wpedantic -xc++ z.cpp
struct S {
int n;
int a[];
} s;
extern int a[];
enum E {
e = sizeof s.a, // rejected in C, accepted in C++
f = sizeof a // rejected in both C and C++
};
z.cpp:3:11: warning: ISO C++ forbids zero-size array ‘a’ [-Wpedantic]
int a[];
^
z.cpp:10:16: error: invalid application of ‘sizeof’ to incomplete type ‘int []’
f = sizeof a // rejected in both C and C++
^
