Comment by spc476

7 days ago

For adapting code to different versions of libraries for one thing:

    #if defined(__SunOS)
        presult = getprotobyname_r(proto,&result,tmp,sizeof(tmp));
        if (presult == NULL)
          return luaL_error(L,"protocol: %s",strerror(errno));
    #elif defined(__linux__)
        if (getprotobyname_r(proto,&result,tmp,sizeof(tmp),&presult) != 0)
          return luaL_error(L,"protocol: %s",strerror(errno));
    #else
        presult = getprotobyname(proto);
        if (presult == NULL)
          return luaL_error(L,"protocol: %s",strerror(errno));
        result = *presult;
    #endif

The sometimes annoyingly small differences between platforms.

14 comments

spc476

lerno 7 days ago

Oh, I think you missed something then:

There is both `$if` and `$switch` compile time statements for this: https://c3-lang.org/generic-programming/compiletime/#if-and-...

At the top level and `@if` attribute is used to achieve the same thing: https://c3-lang.org/language-common/attributes/#if

owlstuffing 7 days ago
Ah. The top-level lang description claims “No preprocessor”, but my definition of that word doesn’t appear to be the same as yours :/
- lerno 6 days ago
  
  The difference here is that a preprocessor runs before parsing and semantic analysis. In C3 compile time if runs in the analysis step, so after parsing.
  So the macros and compile time execution occurs after parsing in C3, but in C everything happens at lexing, before the code is parsed.
  
  11 replies →