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| Path | csiph.com!eternal-september.org!feeder.eternal-september.org!nntp.eternal-september.org!.POSTED!not-for-mail |
|---|---|
| From | Tim Rentsch <tr.17687@z991.linuxsc.com> |
| Newsgroups | comp.lang.c |
| Subject | Re: Why is this happening? |
| Date | Sun, 29 Mar 2026 10:37:23 -0700 |
| Organization | A noiseless patient Spider |
| Lines | 38 |
| Message-ID | <867bqu35bg.fsf@linuxsc.com> (permalink) |
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Richard Harnden <richard.nospam@gmail.invalid> writes: > On 29/03/2026 10:33, David Brown wrote: > >> On 28/03/2026 17:58, Richard Harnden wrote: >> >>> On 28/03/2026 15:35, David Brown wrote: >>> >>>> Well, underscore basically counts as a letter, so it's a valid >>>> identifier just like "x1234" would be. Sometimes people use >>>> identifiers like that for specific purposes, like macro >>>> parameters. >>> >>> Isn't _UPPERCASE and __anything reserved for the implementation? >> >> Yes. >> >> And identifiers with _lowercase have implicit internal linkage (when >> they would otherwise have had implicit external linkage). That's >> why I wrote "underscore /basically/ counts as a letter" - to save >> mentioning all the details. > > I didn't know that, thanks. Don't believe everything you read. Of course, as far as the C standard is concerned, defining a reserved name is undefined behavior, but actual compilers have different behavior than what is suggested above. > So, at file scope, these are equivalent ... ? > static int foo; > int _foo; If you try with gcc or clang (which I did), I expect you will find that _foo is an ordinary global symbol. It does not have "implicit internal linkage". It is treated just like any other external definition.
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Re: Why is this happening? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-29 10:37 -0700
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