9a5f95a82c
The purpose of this macro is to further reduce the number of allocations which occur when dealing with formatting strings. This macro will perform all of the static analysis necessary to validate that a format string is safe, and then it will wrap up the "format string" into an opaque struct which can then be passed around. Two safe functions are added (write/format) which take this opaque argument structure, unwrap it, and then call the unsafe version of write/format (in an unsafe block). Other than these two functions, it is not intended for anyone to ever look inside this opaque struct. The macro looks a bit odd, but mostly because of rvalue lifetimes this is the only way for it to be safe that I know of. Example use-cases of this are: * third-party libraries can use the default formatting syntax without any forced allocations * the fail!() macro can avoid allocating the format string * the logging macros can avoid allocation any strings
15 lines
598 B
Rust
15 lines
598 B
Rust
// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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fn main() {
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format_args!("test"); //~ ERROR: expected token
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format_args!("", || {}); //~ ERROR: must be a string literal
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}
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