https://github.com/JonasToth updated
https://github.com/llvm/llvm-project/pull/118209
>From b10c536f66521249a374908f0bd0eb1fe2ff42ad Mon Sep 17 00:00:00 2001
From: Jonas Toth <developm...@jonas-toth.eu>
Date: Sun, 1 Dec 2024 12:02:13 +0100
Subject: [PATCH] [clang-tidy][docs] improve documentation on
cppcoreguidelines-narrowing-conversions (#111510)
---
.../narrowing-conversions.rst | 23 +++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git
a/clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines/narrowing-conversions.rst
b/clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines/narrowing-conversions.rst
index 04260e75aa558f..f88f9101d00707 100644
---
a/clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines/narrowing-conversions.rst
+++
b/clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines/narrowing-conversions.rst
@@ -27,6 +27,29 @@ This check will flag:
- All applications of binary operators with a narrowing conversions.
For example: ``int i; i+= 0.1;``.
+Note that arithmetic with integer types may perform implicit conversions if
the used integer types are smaller than ``int``.
+These rules are documented under `"Integral Promotion" on this
cppreference.com
<https://en.cppreference.com/w/cpp/language/implicit_conversion>`_
+page. The following example demonstrates this behavior and can be explored
with `cppinsights.io <https://cppinsights.io/s/68553908>`_.
+
+.. code-block:: c++
+
+ // The following function definition demonstrates usage of arithmetic with
integer types smaller than `int`
+ // and how the narrowing conversion happens implicitly.
+ void computation(short argument1, short argument2) {
+ // Arithmetic written by humans:
+ short result = argument1 + argument2;
+ // Arithmetic actually performed by C++:
+ short result = static_cast<short>(static_cast<int>(argument1) +
static_cast<int>(argument2));
+ }
+
+ void recommended_with_gsl(short argument1, short argument2) {
+ // This will throw an exception if the conversion will be lossy.
+ short result = gsl::narrow<short>(argument1 + argument2);
+ // This will just cast through and may yield incorrect results if the sum
is not representable
+ // by `short`.
+ short result = gsl::narrow_cast<short>(argument1 + argument2);
+ }
+
Options
-------
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