how to make this function nothrow?

[Ali Çehreli]

On 2/15/21 1:04 PM, Jack wrote:

 > I have to make my function nothrow because the function that calls it
 > (not written by me) is nothrow. So I need to wrap my code in a
 > try-catch() but how will I report the error message, if the toString()
 > from Throwable isn't nothrow? how do I get out this circular dependence?

I understand that the caller is not written by you but I hope it at 
least expects an 'int' code from f(). The following "last error" is a 
common way for no-exception languages like C. I put the fprintf in g() 
but you can put it at a higher level that you control. You can print 
fLastError when g() fails.

string fLastError;

int f() nothrow
{
   import std.conv : to;
   fLastError = null;

   try {
     "hi".to!int;

   } catch(Throwable th) {
     import std.format;
     fLastError = __FUNCTION__ ~ " failed: " ~ th.msg;
     return 1;
   }

   return 0;
}

int g() nothrow {
   const err = f();
   if (err) {
     import core.stdc.stdio : fprintf, stderr;
     fprintf(stderr, "%.*s\n", cast(int)fLastError.length, fLastError.ptr);
   }

   return err;
}

int main() {
   return g();
}

Ali