Re: how to make this function nothrow?

[Jack via Digitalmars-d-learn]

On Tuesday, 16 February 2021 at 00:39:33 UTC, Steven 
Schveighoffer wrote:

On 2/15/21 4:04 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?



void f() nothrow
{
   import std.conv : to;

     try
     {
     // do something
     }
     catch(Throwable th)
     {
     auto err = th.toString;
     }
}

I can't use err variable, it result in error:

function object.Throwable.toString is not nothrow

obviously, insert a try-catch() within catch() is a circular 
dependence and doesn't solve the problem either (even if it, I 
think it would be quite ugly)


https://dlang.org/phobos/std_exception.html#assumeWontThrow

import std.exception;

auto err = assumeWontThrow(th.toString, "oops, toString threw 
something!");


-Steve


I didn't know about that function, I'll be using this one from 
now. Thanks!

Adam and Ali thank you guys too, helpful always

Re: how to make this function nothrow?

[Steven Schveighoffer via Digitalmars-d-learn]

On 2/15/21 4:04 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?



void f() nothrow
{
   import std.conv : to;

     try
     {
     // do something
     }
     catch(Throwable th)
     {
     auto err = th.toString;
     }
}

I can't use err variable, it result in error:

function object.Throwable.toString is not nothrow

obviously, insert a try-catch() within catch() is a circular dependence 
and doesn't solve the problem either (even if it, I think it would be 
quite ugly)


https://dlang.org/phobos/std_exception.html#assumeWontThrow

import std.exception;

auto err = assumeWontThrow(th.toString, "oops, toString threw something!");

-Steve

Re: how to make this function nothrow?

[Ali Çehreli via Digitalmars-d-learn]

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

Re: how to make this function nothrow?

[Adam D. Ruppe via Digitalmars-d-learn]

On Monday, 15 February 2021 at 21:04:50 UTC, Jack wrote:
obviously, insert a try-catch() within catch() is a circular 
dependence and doesn't solve the problem either (even if it, I 
think it would be quite ugly)


well that's prolly the way to do it, just catch Exception and 
like assert(0) if it happens with a static string


assert(0, "exception toString threw");

to completely abort at that point.

how to make this function nothrow?

[Jack via Digitalmars-d-learn]

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?



void f() nothrow
{
  import std.conv : to;

try
{
// do something
}
catch(Throwable th)
{
auto err = th.toString;
}
}

I can't use err variable, it result in error:

function object.Throwable.toString is not nothrow

obviously, insert a try-catch() within catch() is a circular 
dependence and doesn't solve the problem either (even if it, I 
think it would be quite ugly)