[cfe-commits] [PATCH] Add -fcatch-undefined-behavior runtime library

[Richard Smith]

Hi,

The attached patches to compiler-rt and Clang add a new runtime library
which -fcatch-undefined-behavior will call into when it detects undefined
behavior. Output looks like this (complete with Clang-style highlighting if
it's writing to a terminal):

$ echo '
typedef int X;
int main(int argc, char**) {
  return *(X*)argc;
}' | ./bin/clang -x c++ - -fcatch-undefined-behavior
$ ./a.out
*<stdin>:4:10: fatal error: load of misaligned address 0x1 for type 'X'
(aka 'int'), which requires 4 byte alignment*
zsh: illegal hardware instruction (core dumped)  ./a.out
$

I've left -ftrapv's behavior alone, for now at least.

Review appreciated!

Thanks,
Richard
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