diff --git a/libcxx/include/__support/solaris/xlocale.h b/libcxx/include/__support/solaris/xlocale.h
--- a/libcxx/include/__support/solaris/xlocale.h
+++ b/libcxx/include/__support/solaris/xlocale.h
@@ -43,7 +43,7 @@
 }
 
 inline _LIBCPP_HIDE_FROM_ABI unsigned long long
-strtoull_l(const char *__nptr, char **__endptr, int __base, locale_t __loc) 
+strtoull_l(const char *__nptr, char **__endptr, int __base, locale_t __loc)
   return ::strtoull(__nptr, __endptr, __base);
 }
 
diff --git a/libcxx/include/new b/libcxx/include/new
--- a/libcxx/include/new
+++ b/libcxx/include/new
@@ -164,7 +164,7 @@
 public:
   bad_array_new_length() noexcept : bad_alloc("bad array new length") {}
 };
-#endif // defined(_LIBCPP_ABI_VCRUNTIME) && defined(_HAS_EXCEPTIONS) &&_HAS_EXCEPTIONS == 0 
+#endif // defined(_LIBCPP_ABI_VCRUNTIME) && defined(_HAS_EXCEPTIONS) && _HAS_EXCEPTIONS == 0
 
 _LIBCPP_NORETURN _LIBCPP_FUNC_VIS void __throw_bad_alloc();  // not in C++ spec
 
diff --git a/libcxx/src/support/ibm/wcsnrtombs.cpp b/libcxx/src/support/ibm/wcsnrtombs.cpp
--- a/libcxx/src/support/ibm/wcsnrtombs.cpp
+++ b/libcxx/src/support/ibm/wcsnrtombs.cpp
@@ -14,7 +14,7 @@
 // Converts `max_source_chars` from the wide character buffer pointer to by *`src`,
 // into the multi byte character sequence buffer stored at `dst`, which must be
 // `dst_size_bytes` bytes in size. Returns the number of bytes in the sequence
-// converted from *src, excluding the null terminator. 
+// converted from *src, excluding the null terminator.
 // Returns (size_t) -1 if an error occurs and sets errno.
 // If `dst` is NULL, `dst_size_bytes` is ignored and no bytes are copied to `dst`.
 _LIBCPP_FUNC_VIS
diff --git a/libcxx/test/std/algorithms/alg.sorting/sortable_helpers.h b/libcxx/test/std/algorithms/alg.sorting/sortable_helpers.h
--- a/libcxx/test/std/algorithms/alg.sorting/sortable_helpers.h
+++ b/libcxx/test/std/algorithms/alg.sorting/sortable_helpers.h
@@ -17,7 +17,7 @@
 #include <compare>
 #include <iterator>
 #include "test_iterators.h"
-#endif 
+#endif
 
 struct TrivialSortable {
     int value;
@@ -112,7 +112,7 @@
 
   // TODO: some algorithms calls std::__copy
   // std::__copy(contiguous_iterator<int*>, sentinel_wrapper<contiguous_iterator<int*>>, contiguous_iterator<int*>) doesn't seem to work.
-  // It seems that it unwraps contiguous_iterator<int*> into int*, and then it failed because there is no == between int* and 
+  // It seems that it unwraps contiguous_iterator<int*> into int*, and then it failed because there is no == between int* and
   // sentinel_wrapper<contiguous_iterator<int*>>
   using Sent = std::conditional_t<std::contiguous_iterator<Iter>, Iter, sentinel_wrapper<Iter>>;
 
diff --git a/libcxx/test/std/ranges/range.adaptors/range.join.view/types.h b/libcxx/test/std/ranges/range.adaptors/range.join.view/types.h
--- a/libcxx/test/std/ranges/range.adaptors/range.join.view/types.h
+++ b/libcxx/test/std/ranges/range.adaptors/range.join.view/types.h
@@ -364,7 +364,7 @@
 
 struct move_swap_aware_iter {
 
-  // This is a proxy-like iterator where `reference` is a prvalue, and 
+  // This is a proxy-like iterator where `reference` is a prvalue, and
   // `reference` and `value_type` are distinct types (similar to `zip_view::iterator`).
   using value_type = std::pair<int, int>;
   using reference = std::pair<int&, int&>;
diff --git a/libcxx/utils/ci/run-buildbot b/libcxx/utils/ci/run-buildbot
--- a/libcxx/utils/ci/run-buildbot
+++ b/libcxx/utils/ci/run-buildbot
@@ -187,6 +187,9 @@
     # Depends on LC_COLLATE set at the top of this script.
     ! grep -rn '[^ -~]' libcxx/include/ || false
 
+    # Reject code with trailing whitespace
+    ! grep -rn '[[:blank:]]$' libcxx/include libcxx/src libcxx/test || false
+
     # Reject patches that introduce dependency cycles in the headers.
     python3 libcxx/utils/graph_header_deps.py >/dev/null
 ;;