https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70075
Bug ID: 70075
Summary: incorrect initialization of multidimensional VLAs
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: ---
Unlike GCC in C mode, G++ accepts explicitly initialized variable length arrays
(as specified in WG21 N3639,
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3639.html). However,
when initializing VLAs with more elements than explicitly specified in the
initializer, G++ fails to zero-initialize the remaining elements as would be
the case for ordinary arrays.
The following test case demonstrates the problem:
cat z.cpp && /build/gcc-trunk/gcc/xgcc -B /build/gcc-trunk/gcc -Wall -Wextra
-Wpedantic z.cpp && ./a.out
void __attribute__ ((noclone, noinline)) bar (int n)
{
const int m = 2;
char a [m][n] = { { 0, 1, 2 } };
for (int i = 0; i < m; ++i)
for (int j = 0; j < n; ++j)
__builtin_printf ("%hhi ", a [i][j]);
__builtin_printf ("\n");
if (a [0][n - 1] != 0)
__builtin_abort ();
}
int main ()
{
bar (4);
}
z.cpp: In function ‘void bar(int)’:
z.cpp:4:15: warning: ISO C++ forbids variable length array ‘a’ [-Wvla]
char a [m][n] = { { 0, 1, 2 } };
^
0 1 2 12 -1 127 0 0
Aborted (core dumped)
