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Commit2ec477d

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Cope with Readline's failure to track SIGWINCH events outside of input.
It emerges that libreadline doesn't notice terminal window size changeevents unless they occur while collecting input. This is easy to stumbleover if you resize the window while using a pager to look at query output,but it can be demonstrated without any pager involvement. The symptom isthat queries exceeding one line are misdisplayed during subsequent inputcycles, because libreadline has the wrong idea of the screen dimensions.The safest, simplest way to fix this is to call rl_reset_screen_size()just before calling readline(). That causes an extra ioctl(TIOCGWINSZ)for every command; but since it only happens when reading from a tty, theperformance impact should be negligible. A more valid objection is thatthis still leaves a tiny window during entry to readline() wherein deliveryof SIGWINCH will be missed; but the practical consequences of that areprobably negligible. In any case, there doesn't seem to be any good way toavoid the race, since readline exposes no functions that seem safe to callfrom a generic signal handler --- rl_reset_screen_size() certainly isn't.It turns out that we also need an explicit rl_initialize() call, elserl_reset_screen_size() dumps core when called before the first readline()call.rl_reset_screen_size() is not present in old versions of libreadline,so we need a configure test for that. (rl_initialize() is present atleast back to readline 4.0, so we won't bother with a test for it.)We would need a configure test anyway since libedit's emulation oflibreadline doesn't currently include such a function. Fortunately,libedit seems not to have any corresponding bug.Merlin Moncure, adjusted a bit by me
1 parentb648b70 commit2ec477d

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4 files changed

+17
-2
lines changed

4 files changed

+17
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lines changed

‎configure

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -13232,7 +13232,7 @@ if test x"$pgac_cv_var_rl_completion_append_character" = x"yes"; then
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$as_echo"#define HAVE_RL_COMPLETION_APPEND_CHARACTER 1">>confdefs.h
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fi
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forac_funcin rl_completion_matches rl_filename_completion_function
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forac_funcin rl_completion_matches rl_filename_completion_function rl_reset_screen_size
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do:
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as_ac_var=`$as_echo"ac_cv_func_$ac_func"|$as_tr_sh`
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ac_fn_c_check_func"$LINENO""$ac_func""$as_ac_var"

‎configure.in

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1635,7 +1635,7 @@ LIBS="$LIBS_including_readline"
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if test "$with_readline" = yes; then
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PGAC_VAR_RL_COMPLETION_APPEND_CHARACTER
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AC_CHECK_FUNCS([rl_completion_matches rl_filename_completion_function])
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AC_CHECK_FUNCS([rl_completion_matches rl_filename_completion_function rl_reset_screen_size])
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AC_CHECK_FUNCS([append_history history_truncate_file])
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fi
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‎src/bin/psql/input.c

Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -65,6 +65,17 @@ gets_interactive(const char *prompt)
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{
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char*result;
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/*
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* Some versions of readline don't notice SIGWINCH signals that arrive
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* when not actively reading input. The simplest fix is to always
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* re-read the terminal size. This leaves a window for SIGWINCH to be
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* missed between here and where readline() enables libreadline's
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* signal handler, but that's probably short enough to be ignored.
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*/
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#ifdefHAVE_RL_RESET_SCREEN_SIZE
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rl_reset_screen_size();
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#endif
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/* Enable SIGINT to longjmp to sigint_interrupt_jmp */
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sigint_interrupt_enabled= true;
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@@ -330,6 +341,7 @@ initializeInput(int flags)
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charhome[MAXPGPATH];
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useReadline= true;
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rl_initialize();
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initialize_readline();
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useHistory= true;

‎src/include/pg_config.h.in

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -428,6 +428,9 @@
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/* Define to 1 if you have the `rl_filename_completion_function' function. */
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#undef HAVE_RL_FILENAME_COMPLETION_FUNCTION
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/* Define to 1 if you have the `rl_reset_screen_size' function. */
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#undef HAVE_RL_RESET_SCREEN_SIZE
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/* Define to 1 if you have the <security/pam_appl.h> header file. */
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#undef HAVE_SECURITY_PAM_APPL_H
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