• Wulfklaue (17/33) Jun 01 2017 There does not seem to be a type check on calling the C printf...
• Nicholas Wilson (3/36) Jun 01 2017 you want issues.dlang.org
• Jonathan M Davis via Digitalmars-d (12/49) Jun 01 2017 You're literally calling C's printf here, so you're going to get the sam...
• Mike Parker (3/11) Jun 01 2017 That's not a crash. It's an exception. You can catch it and

Wulfklaue <wulfklaue wulfklaue.com> writes:

Some C playing around:

 import core.stdc.stdio;
 
 void main()
 {
     int x = 5;
     printf("The action is:\n%s", x);
 }

There does not seem to be a type check on calling the C printf... 
%s expects a string but entering the wrong type like a integer 
simply dumps down to this.

 The action is:
 object.Error (0): Access Violation

Playing around a bit more and even D can be made to crash:

 import std.stdio : writefln;
 void main()
 {
     int x = 5;
     writefln("The action is:\n%i", x);
 }

 std.format.FormatException C:\D\dmd2\windows\bin\..\..\src\phobos\std\format.d(1744):

Interesting ways to crash the code. I do not think this is 
expected behavior. :)

And yes, i know that %i is not valid in this case but the fact 
that phobos simply crashes with a exception, no proper error 
warning ...

If this error was somewhere in a large code base, it will be hard 
and time consuming to track down as the dumps do not show any 
trace / line error information.

And side note: The first spot i look to report a bug, is on the 
DMD git repository ( and so do a lot of other people these days 
). Do not even know where the bugs are reported here. Not very 
convenient.

Nicholas Wilson <iamthewilsonator hotmail.com> writes:

On Thursday, 1 June 2017 at 08:45:56 UTC, Wulfklaue wrote:
 Some C playing around:

 import core.stdc.stdio;
 
 void main()
 {
     int x = 5;
     printf("The action is:\n%s", x);
 }

 There does not seem to be a type check on calling the C 
 printf... %s expects a string but entering the wrong type like 
 a integer simply dumps down to this.

There is a check in LDC for that.

 The action is:
 object.Error (0): Access Violation

 Playing around a bit more and even D can be made to crash:

 import std.stdio : writefln;
 void main()
 {
     int x = 5;
     writefln("The action is:\n%i", x);
 }

 std.format.FormatException C:\D\dmd2\windows\bin\..\..\src\phobos\std\format.d(1744):

 Interesting ways to crash the code. I do not think this is 
 expected behavior. :)

 And yes, i know that %i is not valid in this case but the fact 
 that phobos simply crashes with a exception, no proper error 
 warning ...

 If this error was somewhere in a large code base, it will be 
 hard and time consuming to track down as the dumps do not show 
 any trace / line error information.

 And side note: The first spot i look to report a bug, is on the 
 DMD git repository ( and so do a lot of other people these days 
 ). Do not even know where the bugs are reported here. Not very 
 convenient.

you want issues.dlang.org

Jonathan M Davis via Digitalmars-d <digitalmars-d puremagic.com> writes:

On Thursday, June 01, 2017 08:45:56 Wulfklaue via Digitalmars-d wrote:
 Some C playing around:
 import core.stdc.stdio;

 void main()
 {

     int x = 5;
     printf("The action is:\n%s", x);

 }

 There does not seem to be a type check on calling the C printf...
 %s expects a string but entering the wrong type like a integer
 simply dumps down to this.

 The action is:
 object.Error (0): Access Violation


You're literally calling C's printf here, so you're going to get the same
behavior as printf, and there is no type checking. If you want type
checking, use writef or writefln.

 Playing around a bit more and even D can be made to crash:
 import std.stdio : writefln;
 void main()
 {

     int x = 5;
     writefln("The action is:\n%i", x);

 }

 std.format.FormatException C:\D\dmd2\windows\bin\..\..


\src\phobos\std\format.d(1744):
 Interesting ways to crash the code. I do not think this is
 expected behavior. :)

 And yes, i know that %i is not valid in this case but the fact
 that phobos simply crashes with a exception, no proper error
 warning ...

 If this error was somewhere in a large code base, it will be hard
 and time consuming to track down as the dumps do not show any
 trace / line error information.

 And side note: The first spot i look to report a bug, is on the
 DMD git repository ( and so do a lot of other people these days
 ). Do not even know where the bugs are reported here. Not very
 convenient.

The format string is a runtime argument. Why would you expect a compile-time
warning?

If you want it to be tested at compile time, then pass the string as a
compile-time argument. e.g.

writefln!"The action is:\n%i"(x);

and that will result in a static assertion failure.

- Jonathan M Davis

Mike Parker <aldacron gmail.com> writes:

On Thursday, 1 June 2017 at 08:45:56 UTC, Wulfklaue wrote:

 Playing around a bit more and even D can be made to crash:

 import std.stdio : writefln;
 void main()
 {
     int x = 5;
     writefln("The action is:\n%i", x);
 }

 std.format.FormatException C:\D\dmd2\windows\bin\..\..\src\phobos\std\format.d(1744):


That's not a crash. It's an exception. You can catch it and 
respond to it.