[libc++] Avoid UB in the no-exceptions mode in a few places

Summary:
A few places in the library seem to behave unexpectedly when the library
is compiled or used with exceptions disabled. For example, not throwing
an exception when a pointer is NULL can lead us to dereference the pointer
later on, which is UB. This patch fixes such occurences.

It's hard to tell whether there are other places where the no-exceptions
mode misbehaves like this, because the replacement for throwing an
exception does not always seem to be abort()ing, but at least this
patch will improve the situation somewhat.

See http://lists.llvm.org/pipermail/libcxx-dev/2019-January/000172.html

Reviewers: mclow.lists, EricWF

Subscribers: christof, jkorous, dexonsmith, libcxx-commits

Differential Revision: https://reviews.llvm.org/D57761

llvm-svn: 353850

1 files changed, 3 insertions, 13 deletions

diff --git a/libcxx/src/locale.cpp b/libcxx/src/locale.cpp
index 18edad73f5b..00eb574ec45 100644
--- a/libcxx/src/locale.cpp
+++ b/libcxx/src/locale.cpp
@@ -468,10 +468,8 @@ locale::__imp::install(facet* f, long id)
 const locale::facet*
 locale::__imp::use_facet(long id) const
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (!has_facet(id))
-        throw bad_cast();
-#endif  // _LIBCPP_NO_EXCEPTIONS
+        __throw_bad_cast();
     return facets_[static_cast<size_t>(id)];
 }
 
@@ -537,12 +535,8 @@ locale::operator=(const locale& other)  _NOEXCEPT
 }
 
 locale::locale(const char* name)
-#ifndef _LIBCPP_NO_EXCEPTIONS
     : __locale_(name ? new __imp(name)
-                     : throw runtime_error("locale constructed with null"))
-#else  // _LIBCPP_NO_EXCEPTIONS
-    : __locale_(new __imp(name))
-#endif
+                     : (__throw_runtime_error("locale constructed with null"), (__imp*)0))
 {
     __locale_->__add_shared();
 }
@@ -554,12 +548,8 @@ locale::locale(const string& name)
 }
 
 locale::locale(const locale& other, const char* name, category c)
-#ifndef _LIBCPP_NO_EXCEPTIONS
     : __locale_(name ? new __imp(*other.__locale_, name, c)
-                     : throw runtime_error("locale constructed with null"))
-#else  // _LIBCPP_NO_EXCEPTIONS
-    : __locale_(new __imp(*other.__locale_, name, c))
-#endif
+                     : (__throw_runtime_error("locale constructed with null"), (__imp*)0))
 {
     __locale_->__add_shared();
 }