[clang-tools-extra] [clang-tidy] Add new check bugprone-unintended-char-ostream-output (PR #127720)

[Oliver Stöneberg via cfe-commits]

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+.. title:: clang-tidy - bugprone-unintended-char-ostream-output
+
+bugprone-unintended-char-ostream-output
+=======================================
+
+Finds unintended character output from ``unsigned char`` and ``signed char`` to an
+``ostream``.
+
+Normally, when ``unsigned char (uint8_t)`` or ``signed char (int8_t)`` is used, it
+is more likely a number than a character. However, when it is passed directly to
+``std::ostream``'s ``operator<<``, resulting in character-based output instead
+of numeric value. This often contradicts the developer's intent to print
+integer values.
+
+.. code-block:: c++
+
+    uint8_t v = 9;
+    std::cout << v; // output '\t' instead of '9'
+
+It could be fixed as
+
+.. code-block:: c++
+
+    std::cout << static_cast<uint32_t>(v);
----------------
firewave wrote:

It is "magic" but I think it might make sense to make sure that the warning is not triggered by it.

https://github.com/llvm/llvm-project/pull/127720