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This is breaking change #45630. The Dart VM has until now restored the terminal settings upon exit to their initial values for stdin, stdout, and stderr. This change removes that automatic behavior in favor of having the program do the restoration. Previously the intention was that dart programs can enable/disable echoing and line buffering and not worry about restoring the original settings. However, the VM doing so unconditionally leads to undesirable behavior e.g. when the program does not care about terminal settings and is sharing a process group with a program that does care. E.g. if dart's output is piped into less(1), then there is a race condition where dart might see the raw terminal settings set by less(1), and if the dart VM exits after less(1) has exited, then it will restore the raw terminal settings, leaving the user with a seemingly defective shell with echo disabled. This race condition can be reproduced using: cat > yes.dart << EOF main() { for (int i = 0; i < 1000000; i++) { print("yes"); } } EOF stty; (sleep 1 && dart yes.dart) | less; stty; stty sane The user will end up with a shell with echo behavior disabled. The stty command shows the current terminal settings, where the difference can be seen, and 'stty sane' fixes the settings before returning to the shell prompt. The 'stty sane' call can be omitted to see the defective shell prompt. This change removes the terminal restoring behavior (added in Dart 2.0.0) and instead asks applications to do the restoration themselves. The new design matches how programs in other programming languages implement interactive input that changes terminal settings. Furthermore the `echoMode` setting now only controls the `echo` local mode and no longer sets the `echonl` local mode on POSIX systems (which controls whether newline are echoed even if the regular echo mode is disabled). The `echonl` local mode is usually turned off in common shell environments. Programs that wish to control the `echonl` local mode can use the new `echoNewlineMode` setting. This change is required to prevent the reoccurence of #30318 when programs manually restore `echoMode`. Windows has further considerations: It also saves the console code pages and restore them if they were not UTF-8. This behavior is retained as it is useful and needed for Dart's output to function properly. ANSI output sequences are also turned on via ENABLE_VIRTUAL_TERMINAL_PROCESSING, which is slightly changed in this change to only rsetore that setting if it wasn't already on for consistency. Closes https://github.com/dart-lang/sdk/issues/36453 Closes https://github.com/dart-lang/sdk/issues/45630 TEST=Reproduced with less as above Change-Id: I2991f9c7f47b97fe475c1ad6edeb769024f8d0db Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/190484 Reviewed-by: Lasse Nielsen <lrn@google.com> Commit-Queue: Alexander Aprelev <aam@google.com> Reviewed-by: Jonas Termansen <sortie@google.com> Reviewed-by: Alexander Aprelev <aam@google.com>
75 lines
1.5 KiB
C++
75 lines
1.5 KiB
C++
// Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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#include "platform/globals.h"
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#if defined(DART_HOST_OS_FUCHSIA)
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#include "bin/stdio.h"
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#include <errno.h>
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#include "platform/signal_blocker.h"
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namespace dart {
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namespace bin {
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bool Stdin::ReadByte(intptr_t fd, int* byte) {
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unsigned char b;
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ssize_t s = TEMP_FAILURE_RETRY(read(fd, &b, 1));
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if (s < 0) {
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return false;
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}
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*byte = (s == 0) ? -1 : b;
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return true;
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}
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bool Stdin::GetEchoMode(intptr_t fd, bool* enabled) {
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errno = ENOSYS;
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return false;
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}
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bool Stdin::SetEchoMode(intptr_t fd, bool enabled) {
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errno = ENOSYS;
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return false;
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}
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bool Stdin::GetEchoNewlineMode(intptr_t fd, bool* enabled) {
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errno = ENOSYS;
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return false;
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}
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bool Stdin::SetEchoNewlineMode(intptr_t fd, bool enabled) {
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errno = ENOSYS;
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return false;
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}
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bool Stdin::GetLineMode(intptr_t fd, bool* enabled) {
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errno = ENOSYS;
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return false;
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}
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bool Stdin::SetLineMode(intptr_t fd, bool enabled) {
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errno = ENOSYS;
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return false;
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}
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bool Stdin::AnsiSupported(intptr_t fd, bool* supported) {
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*supported = false;
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return true;
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}
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bool Stdout::GetTerminalSize(intptr_t fd, int size[2]) {
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errno = ENOSYS;
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return false;
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}
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bool Stdout::AnsiSupported(intptr_t fd, bool* supported) {
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*supported = false;
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return true;
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}
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} // namespace bin
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} // namespace dart
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#endif // defined(DART_HOST_OS_FUCHSIA)
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