NetBSD Problem Report #58206

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Date: Sat, 27 Apr 2024 23:43:24 +0000 (UTC)
From: campbell+netbsd@mumble.net
Reply-To: campbell+netbsd@mumble.net
To: gnats-bugs@NetBSD.org
Subject: sync_with_stdio breaks reads from cin
X-Send-Pr-Version: www-1.0

>Number:         58206
>Category:       lib
>Synopsis:       sync_with_stdio breaks reads from cin
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    lib-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Apr 27 23:45:00 +0000 2024
>Last-Modified:  Sat May 04 11:10:02 +0000 2024
>Originator:     Taylor R Campbell
>Release:        current, 10, 9
>Organization:
The std::NetBSD++ Foundation
>Environment:
>Description:
In C++, std::ios::sync_with_stdio(false) has the side effect that reading from std::cin sets the eof|fail bits and does nothing to attempt a read from file descriptor 0.
>How-To-Repeat:
$ cat cin.cc
#include <iostream>

using std::cin;
using std::cout;

int
main(void)
{
	char buf[1024];

	std::ios::sync_with_stdio(false);
	cin.read(buf, sizeof buf);
	cout << "read " << cin.gcount() << " bytes, "
	     << "state " << cin.rdstate()
	     << " (eof|fail = " << (cin.eofbit|cin.failbit) << ")"
	     << std::endl;
	return 0;
}
$ make cin CXXFLAGS=-std=c++11
c++ -std=c++11   -o cin cin.cc 
$ echo foo | ./cin
read 0 bytes, state 6 (eof|fail = 6)

If I remove sync_with_stdio:

$ echo foo | ./cin
read 4 bytes, state 6 (eof|fail = 6)
>Fix:
Yes, please!

>Audit-Trail:
From: "Taylor R Campbell" <riastradh@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/58206 CVS commit: src
Date: Sun, 28 Apr 2024 01:21:27 +0000

 Module Name:	src
 Committed By:	riastradh
 Date:		Sun Apr 28 01:21:27 UTC 2024

 Modified Files:
 	src/distrib/sets/lists/debug: mi
 	src/distrib/sets/lists/tests: mi
 	src/etc/mtree: NetBSD.dist.tests
 Added Files:
 	src/tests/lib/libstdc++: Makefile h_cin_nosync.cc t_sync_with_stdio.sh

 Log Message:
 libstdc++: Add test for PR lib/58206, sync_with_stdio busted.


 To generate a diff of this commit:
 cvs rdiff -u -r1.432 -r1.433 src/distrib/sets/lists/debug/mi
 cvs rdiff -u -r1.1312 -r1.1313 src/distrib/sets/lists/tests/mi
 cvs rdiff -u -r1.203 -r1.204 src/etc/mtree/NetBSD.dist.tests
 cvs rdiff -u -r0 -r1.1 src/tests/lib/libstdc++/Makefile \
     src/tests/lib/libstdc++/h_cin_nosync.cc \
     src/tests/lib/libstdc++/t_sync_with_stdio.sh

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

From: Taylor R Campbell <riastradh@NetBSD.org>
To: gnats-bugs@NetBSD.org
Cc: 
Subject: Re: lib/58206: sync_with_stdio breaks reads from cin
Date: Mon, 29 Apr 2024 19:37:26 +0000

 Followup change to fix build with new test in case of pullups:

 https://mail-index.netbsd.org/source-changes/2024/04/28/msg151018.html

From: "Leonardo Taccari" <leot@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/58206 CVS commit: pkgsrc/security/git-crypt
Date: Sat, 4 May 2024 11:07:17 +0000

 Module Name:	pkgsrc
 Committed By:	leot
 Date:		Sat May  4 11:07:17 UTC 2024

 Modified Files:
 	pkgsrc/security/git-crypt: distinfo
 	pkgsrc/security/git-crypt/patches: patch-util.cpp

 Log Message:
 git-crypt: Reference PR lib/58206

 Seems exactly the same problem. Add a reference to it so once it is
 addressed we can wait a couple of years and G/C this patch too.


 To generate a diff of this commit:
 cvs rdiff -u -r1.1 -r1.2 pkgsrc/security/git-crypt/distinfo
 cvs rdiff -u -r1.1 -r1.2 pkgsrc/security/git-crypt/patches/patch-util.cpp

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

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