[PATCH] D55749: [Driver] Automatically enable -munwind-tables if -fseh-exceptions is enabled

[Reid Kleckner via Phabricator via cfe-commits]

rnk added inline comments.


================
Comment at: lib/Driver/ToolChains/Clang.cpp:3929
+      options::OPT_fno_asynchronous_unwind_tables,
+      (TC.IsUnwindTablesDefault(Args) ||
+       (ExceptionArg &&
----------------
Can you put this logic in the Windows or mingw toolchain instead by overriding IsUnwindTablesDefault? -fseh-exceptions feels fairly target specific.

If not, this boolean default feels fairly complicated. Here's how I would restructure it:
```
bool UnwindTables = false;
if (!Freestanding)
  UnwindTables = TC.IsUnwindTablesDefault(Args) || TC.getSanitizerArgs().needsUnwindTables();
UnwindTables = Args.hasFlag(OPT_fasync..., OPT_fno_async..., UnwindTables);
UnwindTables = Args.hasFlag(OPT_munwind_tables, OPT_mno_unwind_tables, UnwindTables);
```
Basically, we have some defaults dictated by the toolchain, and then two boolean flags, where one takes precedence over the other. -fno-async by itself will disable unwind tables, but `-munwind-tables -fno-asynchronous-unwind-tables` will leave them enabled, despite not following the usual "last flag wins" logic.


Repository:
  rC Clang

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D55749/new/

https://reviews.llvm.org/D55749