[libc] [llvm] [libc] Add hardening for FixedVector data structure and fix exposed bug. (PR #122159)

[Michael Jones via llvm-commits]

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@@ -23,55 +24,71 @@ template <typename T, size_t CAPACITY> class FixedVector {
   size_t item_count = 0;
 
 public:
-  constexpr FixedVector() = default;
+  LIBC_INLINE constexpr FixedVector() = default;
 
   using iterator = typename cpp::array<T, CAPACITY>::iterator;
-  constexpr FixedVector(iterator begin, iterator end) : store{}, item_count{} {
+  LIBC_INLINE constexpr FixedVector(iterator begin, iterator end) : store{}, item_count{} {
     for (; begin != end; ++begin)
-      push_back(*begin);
+      LIBC_ASSERT(push_back(*begin));
   }
 
   using const_iterator = typename cpp::array<T, CAPACITY>::const_iterator;
-  constexpr FixedVector(const_iterator begin, const_iterator end)
+  LIBC_INLINE constexpr FixedVector(const_iterator begin, const_iterator end)
       : store{}, item_count{} {
     for (; begin != end; ++begin)
-      push_back(*begin);
+      LIBC_ASSERT(push_back(*begin));
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michaelrj-google wrote:

I don't know if this is a good idea, since the `LIBC_ASSERT` might get removed in non-debug mode. You might have to do `bool succeeds = push_back(*begin); LIBC_ASSERT(succeeds);` here and elsewhere.

https://github.com/llvm/llvm-project/pull/122159