From: janis_papanagnou+ng@hotmail.com   
      
   On 22.10.2025 13:44, Richard Harnden wrote:   
   > On 22/10/2025 10:32, Janis Papanagnou wrote:   
   >> On 22.10.2025 10:56, pozz wrote:   
   >>>   
   >>>> Switch statements without a default case can lead to unexpected   
   >>>> behavior and incomplete handling of all possible cases. When a switch   
   >>>> statement lacks a default case, if a value is encountered that does   
   >>>> not match any of the specified cases, the program will continue   
   >>>> execution without any defined behavior or handling.   
   >>>   
   >>> Maybe I misunderstood that sentence caused by my bad English. I knew   
   >>> that in case the switch value is not present in any case inside the   
   >>> switch, the program continues without doing anything (in the switch) and   
   >>> without any problem.   
   >>>   
   >>> int x = 3;   
   >>> switch(x) {   
   >>>    case 1: printf("Hello");break;   
   >>>    case 2: printf("World");break;   
   >>> }   
   >>>   
   >>> Will the program execution continue without any defined behaviour?   
   >>   
   >> Your program fragment is well defined.   
   >>   
   >> What the poster certainly tried to express was that in case you   
   >> haven't implemented a complete list of all possible cases and   
   >> also not provided a 'default' to catch all non-specified cases,   
   >> then you might get in troubles with your program, probably by   
   >> possible oversights, future extensions, new data, and whatnot.   
   >>   
   >> Personally I have the habit to always define a default branch,   
   >> and even if that default is impossible to reach you'll find an   
   >> error message (like "internal error with unexpected value...")   
   >> generated at that place.   
   >>   
   > Use an enum, and the compiler will warn you ...   
      
   Maybe. Although I don't recall that the "C"-compilers I formerly   
   used checked enums as you've shown below. - But anyway...   
      
   Enums don't help if you use and compare against (for example)   
   characters that are (for example) got from an external source.   
      
     char * cmds = "CMDQ";    // 'D' maybe added later   
     char cmd;   
     ...some n lines of code...   
     ...get input cmd...   
     ...optionally verify cmd with cmds...   
     ...some more m lines of code...   
     switch (cmd) {   
     case 'C': ...;   
     case 'M': ...;   
     default: printf ("Error: uncaught cmd '%c'\n", cmd);   
     }   
      
   It's good to take precautions and define the 'default' case. YMMV.   
      
   Janis   
      
   >   
   > $ cat x.c   
   > #include    
   >   
   > enum x {A, B, C};   
   >   
   > int main(void)   
   > {   
   >     enum x x = C;   
   >   
   >     switch (x)   
   >     {   
   >         case A:   
   >             printf("A\n");   
   >             break;   
   >   
   >         case B:   
   >             printf("B\n");   
   >             break;   
   >     }   
   >   
   >     return 0;   
   > }   
   >   
   > $ gcc -Wall x.c   
   > x.c: In function ‘main’:   
   > x.c:9:9: warning: enumeration value ‘C’ not handled in switch [-Wswitch]   
   >     9 |         switch (x)   
   >       |         ^~~~~~   
   >   
   >   
   >   
      
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