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Subject: Re: Failed assertion dialog box ATTN: Takashi Yano
Thread-Topic: Failed assertion dialog box ATTN: Takashi Yano
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Date: Thu, 19 Nov 2020 21:53:05 +0000
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From: =?utf-8?q?Andr=C3=A9_Bleau_via_Cygwin?= <cygwin@cygwin.com>
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De : Cygwin <cygwin-bounces@cygwin.com> de la part de Thomas Wolff <redacted>
Envoyé : 19 novembre 2020 13:30
À : cygwin@cygwin.com <cygwin@cygwin.com>
Objet : Re: Failed assertion dialog box ATTN: Takashi Yano 
 
---------------------------------------------------------------------------------------

Am 19.11.2020 um 15:21 schrieb André Bleau via Cygwin:
> ...
> Here's some more info:
>
> It seems the bug is related to pseudo-console support; that explains why it is Windows 10 specific.
>
> Experiment:
>
> CYGWIN=disable_pcon /usr/bin/mintty &
>
> In the newly created window:
>
> $ ./a.exe </dev/null >output.txt 2>&1
> Aborted (core dumped)
>
> No message box popup.
>
> $ cat output.txt
> assertion "false" failed: file "assert.cpp", line 3, function: int main()
>
> In the original mintty window, with empty CYGWIN env variable:
>
> $ ./a.exe </dev/null >output.txt 2>&1
> Aborted (core dumped)
>
> A message box pops
>
> AND:
>
> $ cat output.txt
>
>   output.txt  is empty
>
> So, 2 problems here.
>
> In a CMD Window:
>
> set path=%PATH%D:\Cygwin\bin;
> a.exe <NUL: >outcmd.txt 2>&1
>        1 [main] a 759 cygwin_exception::open_stackdumpfile: Dumping stack trace to a.exe.stackdump
>
> type outcmd.txt
> assertion "false" failed: file "assert.cpp", line 3, function: int main()
>        1 [main] a 759 cygwin_exception::open_stackdumpfile: Dumping stack trace to a.exe.stackdump
>
> The bug could be in cygwin or in mintty. Maybe this is something that Thomas Wolff (mintty author) or Takashi Yano  (pseudo-console support expert) would want to look at.
> ---------------------------------------------------------------------------------------
>
> OK, I opened an issue for mintty and it was quickly closed with that quote:
>
> "Quick generic answer: if it's caused by ConPTY support, it's not related to mintty; also mintty never shows any popups.
> Funny thing, though, but really: assert isn't handled by the terminal."
>
> So the issue can only be with pseudo-console support in cygwin.
It does not seem to happen in xterm which is weird.
It does however also happen in rxvt-unicode, xfce4-terminal, and vte.
The message text of the popup can be easily found in cygwin code.
Thomas
---------------------------------------------------------------------------------------

One more data point:

The following program:

$ cat stderr.c
#include <stdio.h>
int main() {
  fprintf(stdout, "To stdout\n");
  fprintf(stderr, "To stderr\n");
  return 0;
}

$ gcc stderr.c
$ ./a.exe </dev/null >output.txt 2>&1

Behaves normally, with either empty CYGWIN env variable or with 
$ CYGWIN=disable_pcon /usr/bin/mintty &

So the problem is narrowly confined to how Cygwin handles assert when pseudo-console is used and stdin, stdout, and stderr are redirected. Not in all cases where pseudo-console is used and stdin, stdout, and stderr are redirected. 

- André Bleau
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