Re: io_write (io.c) bug (and its fix) under MS Windows for GUI apps (rubyw)

Is it good style to #ifdef the if statement guard?

Does ProcessHasConsole return the right value when:

(a) The console's title is more than 127 characters? MSDN says "total
size of the buffer required will be less than 64K."

(b) When the console's title is blank? MSDN says "If the function
succeeds, the return value is the length of the string copied to the
buffer, in characters. If the buffer is not large enough to store the
title, the return value is zero and GetLastError returns
ERROR_SUCCESS." Does that mean empty string => \0 => return value 1?
Have you tried it out?

I think a better bet would be:

if (GetStdHandle(STD_OUTPUT_HANDLE)) // or STD_ERROR_HANDLE, as appropriate

would be safer. You might want to test for INVALID_HANDLE_VALUE as well as NULL.

Dominic Cooney

On 11/19/06, Mounir Idrassi <[e-mail]> wrote:
> Hi all,
> I recently encountered a problem under MS Windows where a GUI
> application that runs correctly with ruby.exe refused to start with
> rubuw.exe (1.8.5 version). After some digging I found that the problem
> came from the function io_write in io.c : rb_sys_fail was called after
> receiving -1 from io_fwrite. Actually, the ruby interpreter wanted to
> print some warning to "rb_stderr" and because its a GUI application
> with no console attached to it the C runtime returned -1. If I use
> ruby.exe instead, the warnings are printed correctly.
> To correct this behavior, it's sufficient to test if we have a console
> attached to the current process and in case no one is found, we don't
> call rb_sys_fail if the target stream is either rb_stderr ou
> rb_stdout.
> I made the following modifications to implement this :
>
>     - Add a function named "ProcessHasConsole" in case we are
> compiling for MS Windows that returns TRUE if a console is attached to
> the current process and FALSE otherwise. You can find its body at the
> end of this email.
>
>     - In "io_write" body, replace the statement "if (n == -1)
> rb_sys_fail(fptr->path);" with the following :
>                if (n == -1)
>                {
>                   #ifdef _WIN32
>                   if( (io != rb_stderr && io != rb_stdout) ||
> ProcessHasConsole())
>                   #endif
>                   rb_sys_fail(fptr->path);
>                }
>
> I hope this can help Windows users of ruby that were affected by the
> same problem as me.
> Is there any specific protocol for submitting patches?
>
> Cheers,
>
> Mounir IDRASSI
> IDRIX
> web: http://www.idrix.fr
>
> PS: body of the function  "ProcessHasConsole" :
>
> #ifdef _WIN32
> static BOOL ProcessHasConsole()
> {
>        TCHAR szTitle[128];
>        if(GetConsoleTitle(szTitle,128) || GetLastError() == ERROR_SUCCESS)
>                 return TRUE;
>        else
>                 return FALSE;
> }
> #endif
>
>