[libcxx] Initialize vcruntime __std_exception_data in the exception copy ctor

[mstorsjo]

This fixes failures in a number of tests, in the
clang-cl-no-vcruntime configuration (where libcxx provides dummy, no-op replacements of some vcruntime base exception classes), if building with optimization enabled.

Previously, with optimization enabled, the compiler concluded that these fields would be uninitialized at the points of asserts in the tests.

This fixes the following tests in this configuration:

llvm-libc++-shared-no-vcruntime-clangcl.cfg.in :: std/language.support/support.dynamic/alloc.errors/bad.alloc/bad_alloc.pass.cpp
llvm-libc++-shared-no-vcruntime-clangcl.cfg.in :: std/language.support/support.dynamic/alloc.errors/new.badlength/bad_array_new_length.pass.cpp
llvm-libc++-shared-no-vcruntime-clangcl.cfg.in :: std/language.support/support.exception/bad.exception/bad_exception.pass.cpp
llvm-libc++-shared-no-vcruntime-clangcl.cfg.in :: std/language.support/support.exception/exception/exception.pass.cpp
llvm-libc++-shared-no-vcruntime-clangcl.cfg.in :: std/language.support/support.rtti/bad.cast/bad_cast.pass.cpp
llvm-libc++-shared-no-vcruntime-clangcl.cfg.in :: std/language.support/support.rtti/bad.typeid/bad_typeid.pass.cpp

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Martin Storsjö (mstorsjo)

Changes

This fixes failures in a number of tests, in the
clang-cl-no-vcruntime configuration (where libcxx provides dummy, no-op replacements of some vcruntime base exception classes), if building with optimization enabled.

Previously, with optimization enabled, the compiler concluded that these fields would be uninitialized at the points of asserts in the tests.

This fixes the following tests in this configuration:

llvm-libc++-shared-no-vcruntime-clangcl.cfg.in :: std/language.support/support.dynamic/alloc.errors/bad.alloc/bad_alloc.pass.cpp
llvm-libc++-shared-no-vcruntime-clangcl.cfg.in :: std/language.support/support.dynamic/alloc.errors/new.badlength/bad_array_new_length.pass.cpp
llvm-libc++-shared-no-vcruntime-clangcl.cfg.in :: std/language.support/support.exception/bad.exception/bad_exception.pass.cpp
llvm-libc++-shared-no-vcruntime-clangcl.cfg.in :: std/language.support/support.exception/exception/exception.pass.cpp
llvm-libc++-shared-no-vcruntime-clangcl.cfg.in :: std/language.support/support.rtti/bad.cast/bad_cast.pass.cpp
llvm-libc++-shared-no-vcruntime-clangcl.cfg.in :: std/language.support/support.rtti/bad.typeid/bad_typeid.pass.cpp

---

Full diff: https://github.com/llvm/llvm-project/pull/144329.diff

1 Files Affected:

• (modified) libcxx/include/__exception/exception.h (+1-1)

diff --git a/libcxx/include/__exception/exception.h b/libcxx/include/__exception/exception.h
index f7dab6e83ad14..161cc49979e4a 100644
--- a/libcxx/include/__exception/exception.h
+++ b/libcxx/include/__exception/exception.h
@@ -48,7 +48,7 @@ class exception { // base of all library exceptions
     __data_._DoFree = true;
   }
 
-  exception(exception const&) _NOEXCEPT {}
+  exception(exception const&) _NOEXCEPT : __data_() {}
 
   exception& operator=(exception const&) _NOEXCEPT { return *this; }