VLAs should be deallocated on a jump to before their definition, including a jump to a label in an inner scope. void *volatile p; int main (void) { int n = 0; if (0) { lab:; } int x[n % 1000 + 1]; x[0] = 1; x[n % 1000] = 2; p = x; n++; if (n < 1000000) goto lab; return 0; } should execute successfully. (Mentioned in <http://gcc.gnu.org/ml/gcc-patches/2004-08/msg00738.html>.)
Confirmed.
The problem here is that the C front end is not creating a new BIND_EXPR for the scope starting at the declaration for X. Insert one by hand and you'll see that the tree optimizers are doing the right thing.
Created attachment 17557 [details] Always create a new BIND_EXPR for VLA decls I tried to make use of scopes: If a label is defined in a parent scope, start a new BIND_EXPR. This did not work. So the attached patch takes the brute-force approach. When optimizing, this _should_ not hurt, but we get two __builtin_stack_restore calls now. Apparently Jakub's PR23848 fix doesn't work for our case. Anyway, this patch does, of course, make the test case of comment #0 run.
Jakub, this is what we discussed last night.
Subject: Bug 19771 Author: jsm28 Date: Sun Apr 19 20:19:54 2009 New Revision: 146358 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=146358 Log: PR c/19771 * c-semantics.c (pop_stmt_list): Propagate STATEMENT_LIST_HAS_LABEL to parent statement list. testsuite: * gcc.c-torture/execute/vla-dealloc-1.c: New test. Added: trunk/gcc/testsuite/gcc.c-torture/execute/vla-dealloc-1.c Modified: trunk/gcc/ChangeLog trunk/gcc/c-semantics.c trunk/gcc/testsuite/ChangeLog
Fixed for 4.5.