CWG2811 [basic.start.main] Clarify what it means to "use" main #422

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1. eisenwave commented on Sep 12, 2023

   

   eisenwave

   on Sep 12, 2023

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   On a side note, this may have a normative effect on [basic.start.dynamic] p5 because whether "use" of main constitutes odr-use impacts until when dynamic initialization can be deferred exactly.

   See also Stack Overflow/Why are exceptions thrown during deferred dynamic initialization not caught by main?
2. frederick-vs-ja commented on Sep 13, 2023

   

   frederick-vs-ja

   on Sep 13, 2023

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   Or perhaps someone (like Clang folks?) may want to strengthen the prohibition:

   The function main shall not be used within the program. An expression shall not name ([basic.def.odr]) the function main in the global scope.
3. xmh0511 commented on Sep 20, 2023

   

   xmh0511

   on Sep 20, 2023

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   Or perhaps someone (like Clang folks?) may want to strengthen the prohibition:

   The function main shall not be used within the program. An expression shall not name ([basic.def.odr]) the function main in the global scope.

   I think "in the global socpe" can arise ambiguities. What does it mean?

   1. Does it mean the expression that appears in other namespaces other than global scope will be ok?
      2.Or, It means the function main that inhabits the global scope

   Your intent presumably is the second one.

   An expression shall not name the function main whose declaration's target scope is the global scope.

   int main(){}
   namespace A{
      int main();
      void fun(){
         extern int main();  
         main;  // ok
      }
      void g(){
        using ::main;
        main; // error
      }
   }
4. t3nsor commented on Sep 20, 2023

   

   t3nsor

   on Sep 20, 2023

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   Honestly we could just say "the function ::main shall not be odr-used". No need to overcomplicate things.

   Or "an id-expression that names the function ::main is ill-formed."
5. eisenwave commented on Sep 21, 2023

   

   eisenwave

   on Sep 21, 2023

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   @t3nsor the term usually used in the standard is "main function". There are 12 occurrences of it throughout various sections. Instead of "the function ::main", everywhere should just state "the ::main function".

   This could be done through an editorial change where all those are updated to "::main function". This is purely editorial because the intent is entirely clear.
6. eisenwave commented on Sep 21, 2023

   

   eisenwave

   on Sep 21, 2023

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   @xmh0511 I see no value in keeping the arbitrary restriction that you can't even name ::main at all (assuming that this restriction is the current intended behavior, which isn't clear). The people over at llvm-project haven't made a case for keeping their current strict implementation either.

   There could actually be value in detecting the type of main within a macro.
7. jensmaurer commented on Oct 18, 2023

   

   jensmaurer

   on Oct 18, 2023

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   CWG2811
8. jensmaurer

   changed the title [-][basic.start.main] Clarify what it means to "use" `main`[/-] [+]CWG2811 [basic.start.main] Clarify what it means to "use" `main`[/+] on Oct 18, 2023
9. tkoeppe

   closed this as completedin draft#6906on Apr 15, 2024