https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88261
--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
The ICE only affects C++. G++ 8 and prior accept the code with just a pedantic
warning:
$ cat pr88261.C && gcc -O2 -S -Wall -Wextra -Wpedantic pr88261.C
struct str { int len; char s[]; };
void foo()
{
struct str c = { 2, "c" };
}
pr88261.C:1:30: warning: ISO C++ forbids flexible array member ‘s’ [-Wpedantic]
struct str { int len; char s[]; };
^
pr88261.C: In function ‘void foo()’:
pr88261.C:5:27: warning: initialization of a flexible array member [-Wpedantic]
struct str c = { 2, "c" };
^
pr88261.C:5:14: warning: unused variable ‘c’ [-Wunused-variable]
struct str c = { 2, "c" };
^
But G++ rejects the code if it's changed like below so the C++ front-end should
probably reject it regardless of whether or not the struct is used.
int foo()
{
struct str c = { 2, "c" };
return c.s[0];
}
pr88261.C:1:30: warning: ISO C++ forbids flexible array member ‘s’ [-Wpedantic]
struct str { int len; char s[]; };
^
pr88261.C: In function ‘int foo()’:
pr88261.C:5:27: warning: initialization of a flexible array member [-Wpedantic]
struct str c = { 2, "c" };
^
pr88261.C:5:14: error: invalid use of array with unspecified bounds
struct str c = { 2, "c" };
^
pr88261.C:5:14: error: invalid use of array with unspecified bounds
The again, G++ 5 accepts the modified example above with -fpermissive:
pr88261.C:5:27: warning: initializer-string for array of chars is too long
[-fpermissive]
struct str c = { 2, "c" };
^
