[libcxx-commits] [libcxx] [libc++] Fix wraparound issue with -fsanitize=integer in string operator>> (PR #106263)

[Louis Dionne via libcxx-commits]

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@@ -1211,12 +1211,11 @@ operator>>(basic_istream<_CharT, _Traits>& __is, basic_string<_CharT, _Traits, _
     try {
 #endif
       __str.clear();
-      streamsize __n = __is.width();
-      if (__n <= 0)
-        __n = __str.max_size();
-      if (__n <= 0)
-        __n = numeric_limits<streamsize>::max();
-      streamsize __c            = 0;
+      using _Size               = typename basic_string<_CharT, _Traits, _Allocator>::size_type;
+      streamsize const __width  = __is.width();
+      _Size const __max_size    = __str.max_size();
+      _Size const __n           = __width <= 0 ? __max_size : std::min(__max_size, static_cast<_Size>(__width));
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ldionne wrote:

If `width` is <= 0, we use `max_size()` as-is. Otherwise, we use the smallest of `width` and `max_size()`, which accounts for the case where `max_size()` would be e.g. a 32 bit integer.

https://github.com/llvm/llvm-project/pull/106263