tidy - modernize-use-std-format — Extra Clang Tools 22.0.0git documentation (original) (raw)

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:🧵:c_str() andstd:🧵:data().

For example, it turns lines like

return absl::StrFormat("The %s is %3d", description.c_str(), value);

into:

return std::format("The {} is {:3}", description, value);

The check uses the same format-string-conversion algorithm asmodernize-use-std-print and its shortcomings and behaviour in combination with macros are described in the documentation for that check.

Options¶

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_tand 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, withStrictMode enabled,

extern std::string strprintf(const char *format, ...); int i = -42; unsigned int u = 0xffffffff; return strprintf("%u %d\n", i, u);

would be converted to

return std::format("{} {}\n", static_cast(i), static_cast(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 ofStrFormatLikeFunctions since absl::StrFormat takes a function parameter pack and is not a variadic function.

StrFormatLikeFunctions¶

A semicolon-separated list of regular expressions matching the (fully qualified) names of functions to replace, with the requirement that the first parameter contains the printf-style format string and the arguments to be formatted follow immediately afterwards. Qualified member function names are supported, but the replacement function name must be unqualified. The default value is absl::StrFormat.

ReplacementFormatFunction¶

The function that will be used to replace the function set by theStrFormatLikeFunctions option rather than the defaultstd::format. It is expected that the function provides an interface that is compatible with std::format. A suitable candidate would befmt::format.

The header that must be included for the declaration ofReplacementFormatFunction so that a #include directive can be added if required. If ReplacementFormatFunction is std::format then this option will default to <format>, otherwise this option will default to nothing and no #include directive will be added.