@matheusbsbs / matheus-bagliano / commits / f7da756566

terminal: pop signal handler when terminal is restored

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> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Phillip Wood committed Feb 22, 2022 at 18:53 UTC f7da756566e8abf18abdf9e30a8ed6d2088770de

2 files changed +21 -4

compat/terminal.c

+13 -4

@@ -11,7 +11,7 @@

11 static void restore_term_on_signal(int sig)

12 {

13 restore_term();

14 - sigchain_pop(sig);

14 + /* restore_term calls sigchain_pop_common */

15 raise(sig);

16 }

@@ -31,14 +31,20 @@ void restore_term(void)

31 tcsetattr(term_fd, TCSAFLUSH, &old_term);

32 close(term_fd);

33 term_fd = -1;

34 + sigchain_pop_common();

35 }

37 int save_term(int full_duplex)

38 {

39 if (term_fd < 0)

40 term_fd = open("/dev/tty", O_RDWR);

41 + if (term_fd < 0)

42 + return -1;

43 + if (tcgetattr(term_fd, &old_term) < 0)

44 + return -1;

45 + sigchain_push_common(restore_term_on_signal);

41 - return (term_fd < 0) ? -1 : tcgetattr(term_fd, &old_term);

47 + return 0;

48 }

50 static int disable_bits(tcflag_t bits)

@@ -49,12 +55,12 @@ static int disable_bits(tcflag_t bits)

55 goto error;

57 t = old_term;

52 - sigchain_push_common(restore_term_on_signal);

59 t.c_lflag &= ~bits;

60 if (!tcsetattr(term_fd, TCSAFLUSH, &t))

61 return 0;

63 + sigchain_pop_common();

64 error:

65 close(term_fd);

66 term_fd = -1;

@@ -100,6 +106,8 @@ void restore_term(void)

106 return;

107 }

108

109 + sigchain_pop_common();

110 +

111 if (hconin == INVALID_HANDLE_VALUE)

112 return;

113

@@ -134,6 +142,7 @@ int save_term(int full_duplex)

142

143 GetConsoleMode(hconin, &cmode_in);

144 use_stty = 0;

145 + sigchain_push_common(restore_term_on_signal);

146 return 0;

147 error:

148 CloseHandle(hconin);

@@ -177,10 +186,10 @@ static int disable_bits(DWORD bits)

186 if (save_term(0) < 0)

187 return -1;

188

180 - sigchain_push_common(restore_term_on_signal);

189 if (!SetConsoleMode(hconin, cmode_in & ~bits)) {

190 CloseHandle(hconin);

191 hconin = INVALID_HANDLE_VALUE;

192 + sigchain_pop_common();

193 return -1;

194 }

195

compat/terminal.h

@@ -1,7 +1,15 @@

1 #ifndef COMPAT_TERMINAL_H

2 #define COMPAT_TERMINAL_H

4 +/*

5 + * Save the terminal attributes so they can be restored later by a

6 + * call to restore_term(). Note that every successful call to

7 + * save_term() must be matched by a call to restore_term() even if the

8 + * attributes have not been changed. Returns 0 on success, -1 on

9 + * failure.

10 + */

11 int save_term(int full_duplex);

12 +/* Restore the terminal attributes that were saved with save_term() */

13 void restore_term(void);

15 char *git_terminal_prompt(const char *prompt, int echo);