================
@@ -0,0 +1,84 @@
+.. title:: clang-tidy - modernize-use-std-format
+
+modernize-use-std-format
+========================
+
+Converts calls to ``absl::StrFormat``, or other functions via
+configuration options, to C++20's ``std::format``, or another function
+via a configuration option, modifying the format string appropriately and
+removing now-unnecessary calls to ``std::string::c_str()`` and
+``std::string::data()``.
+
+For example, it turns lines like
+
+.. code-block:: c++
+
+ return absl::StrFormat("The %s is %3d", description.c_str(), value);
+
+into:
+
+.. code-block:: c++
+
+ return std::format("The {} is {:3}", description, value);
+
+The check uses the same format-string-conversion algorithm as
+`modernize-use-std-print <../modernize/use-std-print.html>`_ and its
+shortcomings are described in the documentation for that check.
+
+Options
+-------
+
+.. option:: StrictMode
+
+ When `true`, the check will add casts when converting from variadic
+ functions and printing signed or unsigned integer types (including
+ fixed-width integer types from ``<cstdint>``, ``ptrdiff_t``, ``size_t``
+ and ``ssize_t``) as the opposite signedness to ensure that the output
+ would matches that of a simple wrapper for ``std::sprintf`` that
+ accepted a C-style variable argument list. For example, with
+ `StrictMode` enabled,
+
+ .. code-block:: c++
+
+ extern std::string strprintf(const char *format, ...);
+ int i = -42;
+ unsigned int u = 0xffffffff;
+ return strprintf("%d %u\n", i, u);
+
+ would be converted to
+
+ .. code-block:: c++
+
+ return std::format("{} {}\n", static_cast<unsigned int>(i),
static_cast<int>(u));
+
+ to ensure that the output will continue to be the unsigned representation
+ of -42 and the signed representation of 0xffffffff (often 4294967254
+ and -1 respectively). When `false` (which is the default), these casts
+ will not be added which may cause a change in the output. Note that this
+ option makes no difference for the default value of
+ `StrFormatLikeFunctions` since ``absl::StrFormat`` takes a function
+ parameter pack and is not a variadic function.
+
+.. option:: StrFormatLikeFunctions
+
+ A semicolon-separated list of (fully qualified) extra function names to
----------------
5chmidti wrote:
The `extra` is wrong here. If you don't pass an option the default is described
later, but when you do pass something, then default `absl::StrFormat` is not
part of the checked function names.
https://github.com/llvm/llvm-project/pull/90397
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