On Fri, Jul 18, 2025 at 10:57 AM Frederick Virchanza Gotham via
Std-Proposals <std-proposals_at_[hidden]> wrote:
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> On Friday, July 18, 2025, David Brown wrote:
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>> Finally, I suggest you stop writing nonsense in your code. A TCP/IP port is a number between 1 and 65535 (UDP allows port 0 in some circumstances to mean "no port"). If you have a number and you want to check its validity as a port number, check it against these two values - 1 and 65535 (or 0xffff if you prefer hex, or define an identifier for it if you think it makes the code clearer). Using "-1" as a maximum value for an unsigned type is nonsense.
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> I have a trick I do with unsigned numbers in multi-threaded programs.
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> I define the variable, maybe something like:
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> std::atomic< std::size_t > n{0u};
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> 0 is an invalid number.
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> The first threads starts the second thread. The second thread assigns to 'n'. If the second thread fails, 'n' remains as zero... but that's a problem if the first thread does this:
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> n.wait(0u);
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> Therefore in the second thread, I set 'n' to its max value upon failure so that the first thread will unblock.
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> So when I'm dealing with an unsigned integer variable shared between multiple threads, I blacklist 0 and its max value as invalid, like this:
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> if ( 0u==n || -1==n ) . . .
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> But from now on I'll write:
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> if ( 0u==n || _Max==n ) . . .

You can't. In accord with [lex.name], identifiers starting with an `_`
followed by a capital letter are reserved for implementation use only.
As such, any user-code that attempts to use such identifiers is
ill-formed, NDR.

> Of course I could instead use a second variable, maybe a semaphore or a condition variable or an atomic boolean, but I like my strategy, which can be summed up as: "If all the bits are the same, it's invalid".

That's fine. Why should the standard committee care about "my strategy"?