[PATCH v2 2/4] terminal: pop signal handler when terminal is restored
- From
- Phillip Wood via GitGitGadget <gitgitgadget@gmail.com>
- Date
- Feb 22, 2022, 18:53 UTC
- Message-ID
- <0020953f1cf901e66883853392915ba8ce07ca61.1645556015.git.gitgitgadget@gmail.com>
- In-Reply-To
- <pull.1146.v2.git.1645556015.gitgitgadget@gmail.com>
From: Phillip Wood <phillip.wood@dunelm.org.uk>
When disable_bits() changes the terminal attributes it uses sigchain_push_common() to restore the terminal if a signal is received before restore_term() is called. However there is no corresponding call to sigchain_pop_common() when the settings are restored so the signal handler is left on the sigchain stack. This leaves the stack unbalanced so code such as
sigchain_push_common(my_handler); ... read_key_without_echo(...); ... sigchain_pop_common();
pops the handler pushed by disable_bits() rather than the one it intended to. Additionally "git add -p" changes the terminal settings every time it reads a key press so the stack can grow significantly.
In order to fix this save_term() now sets up the signal handler so restore_term() can unconditionally call sigchain_pop_common(). There are no callers of save_term() outside of terminal.c as the only external caller was removed by e3f7e01b50 ("Revert "editor: save and reset terminal after calling EDITOR"", 2021-11-22). Any future callers of save_term() should benefit from having the signal handler set up for them.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk> --- compat/terminal.c | 17 +++++++++++++---- compat/terminal.h | 8 ++++++++ 2 files changed, 21 insertions(+), 4 deletions(-)
diff --git a/compat/terminal.c b/compat/terminal.c index fb8c70a6251..11288cfe5c9 100644 --- a/compat/terminal.c +++ b/compat/terminal.c @@ -11,7 +11,7 @@ static void restore_term_on_signal(int sig) { restore_term(); - sigchain_pop(sig); + /* restore_term calls sigchain_pop_common */ raise(sig); } @@ -31,14 +31,20 @@ void restore_term(void) tcsetattr(term_fd, TCSAFLUSH, &old_term); close(term_fd); term_fd = -1; + sigchain_pop_common(); } int save_term(int full_duplex) { if (term_fd < 0) term_fd = open("/dev/tty", O_RDWR); + if (term_fd < 0) + return -1; + if (tcgetattr(term_fd, &old_term) < 0) + return -1; + sigchain_push_common(restore_term_on_signal); - return (term_fd < 0) ? -1 : tcgetattr(term_fd, &old_term); + return 0; } static int disable_bits(tcflag_t bits) @@ -49,12 +55,12 @@ static int disable_bits(tcflag_t bits) goto error; t = old_term; - sigchain_push_common(restore_term_on_signal); t.c_lflag &= ~bits; if (!tcsetattr(term_fd, TCSAFLUSH, &t)) return 0; + sigchain_pop_common(); error: close(term_fd); term_fd = -1; @@ -100,6 +106,8 @@ void restore_term(void) return; } + sigchain_pop_common(); + if (hconin == INVALID_HANDLE_VALUE) return; @@ -134,6 +142,7 @@ int save_term(int full_duplex) GetConsoleMode(hconin, &cmode_in); use_stty = 0; + sigchain_push_common(restore_term_on_signal); return 0; error: CloseHandle(hconin); @@ -177,10 +186,10 @@ static int disable_bits(DWORD bits) if (save_term(0) < 0) return -1; - sigchain_push_common(restore_term_on_signal); if (!SetConsoleMode(hconin, cmode_in & ~bits)) { CloseHandle(hconin); hconin = INVALID_HANDLE_VALUE; + sigchain_pop_common(); return -1; } diff --git a/compat/terminal.h b/compat/terminal.h index e1770c575b2..0fb9fa147c4 100644 --- a/compat/terminal.h +++ b/compat/terminal.h @@ -1,7 +1,15 @@ #ifndef COMPAT_TERMINAL_H #define COMPAT_TERMINAL_H +/* + * Save the terminal attributes so they can be restored later by a + * call to restore_term(). Note that every successful call to + * save_term() must be matched by a call to restore_term() even if the + * attributes have not been changed. Returns 0 on success, -1 on + * failure. + */ int save_term(int full_duplex); +/* Restore the terminal attributes that were saved with save_term() */ void restore_term(void); char *git_terminal_prompt(const char *prompt, int echo);
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