[RFC][patch for gcc12][version 1] add -ftrivial-auto-var-init and variable attribute "uninitialized" to gcc

[Kees Cook]

On Thu, Feb 25, 2021 at 05:56:38PM -0600, Qing Zhao wrote:
> Just noticed that you didn’t add -fauto-var-init-approach=D to the command line.

Ah-ha! I didn't realize that was needed; thanks. However, now some of the sources crash in a different way. Here's the reproducer:

$ cat poc.i
struct a {
  int b;
  int array[];
};
void c() {
  struct a d;
}

$ gcc -ftrivial-auto-var-init=pattern -fauto-var-init-approach=D -c /dev/null poc.i
during RTL pass: expand
poc.i: In function ‘c’:
poc.i:6:12: internal compiler error: in build_pattern_cst, at tree.c:2652
    6 |   struct a d;
      |            ^
0x75b572 build_pattern_cst(tree_node*)
        ../../../gcc/gcc/tree.c:2652
0x10db116 build_pattern_cst(tree_node*)
        ../../../gcc/gcc/tree.c:2612
0xb8a230 expand_DEFERRED_INIT
        ../../../gcc/gcc/internal-fn.c:2980
0x970e17 expand_call_stmt
        ../../../gcc/gcc/cfgexpand.c:2749
0x970e17 expand_gimple_stmt_1
        ../../../gcc/gcc/cfgexpand.c:3844
0x970e17 expand_gimple_stmt
        ../../../gcc/gcc/cfgexpand.c:4008
0x9766b3 expand_gimple_basic_block
        ../../../gcc/gcc/cfgexpand.c:6045
0x9780d6 execute
        ../../../gcc/gcc/cfgexpand.c:6729
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

I assume it's not handling the flex-array happily?

-- 
Kees Cook