https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69517
--- Comment #17 from Martin Sebor <msebor at gcc dot gnu.org> --- (In reply to Jakub Jelinek from comment #16) The bug here is in G++ accepting a VLA initializer with more elements than there is room for in the VLA, and then trashing the stack at runtime with the extra elements. It is a regression with respect to GCC 4.9.3 which implements C++ VLAs as specified in n3639 (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3639.html). This is documented in GCC 4.9 changes (https://gcc.gnu.org/gcc-4.9/changes.html) which highlights the feature using the following example: void f(int n) { int a[n] = { 1, 2, 3 }; // throws std::bad_array_length if n < 3 ... VLAs were subsequently removed from C++, and also partially (but not completely) removed from G++, which causes C++ programs developed and tested with G++ 4.9 to break when ported to a later version. C++ VLAs will be safer to use with the patch referenced in comment #9. It patch had to be reverted from GCC 6.0 because it caused problems in Java. Java has been removed and I plan/hope to resubmit the patch for GCC 8. (I wanted to do it for GCC 7 but didn't get to it.)
