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carbon-lang/bazel
Dana Jansens 239ad9fe8b Disable C++ exceptions in the toolchain (#7532)
Pass `-fno-exceptions` when building the toolchain. We do not use
exceptions, so we do not have any try/catch in main, so uncaught
exceptions just unwind and exit. They do not hit our signal handler and
we do not print the stack trace.

Instead of adding a try/catch in main, and redirecting that, we can
build with `-fno-exceptions`. This turns any throw into an `abort()`.
And indeed with that flag, the following code crashes and prints a stack
trace:
```cpp
  std::variant<int, bool> a = {1};
  std::get<bool>(a);
```

Note that libc++ and libc++abi need to be built with exceptions enabled.
It is explicitly allowed to use different compiler flags when building
these libraries even though they share some headers with users of the
libraries, so this does not cause ODR violations.

Fixes #5225
2026-07-30 20:15:03 +00:00
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