pacman/util: flush terminal input before reading response

Addresses FS#20538

Conflicts:

	src/pacman/util.c

Signed-off-by: Dave Reisner <d@falconindy.com>
Signed-off-by: Dan McGee <dan@archlinux.org>
(cherry picked from commit 9477abc3591905a20acbfe7b8ce7832617d72701)

2 files changed, 24 insertions, 2 deletions

diff --git a/configure.ac b/configure.ac
index c672c66c..f6d5a2c3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -171,7 +171,8 @@ AM_CONDITIONAL([HAVE_LIBFETCH], [test "x$ac_cv_lib_fetch_fetchParseURL" = "xyes"
 # Checks for header files.
 AC_CHECK_HEADERS([fcntl.h glob.h libintl.h locale.h mntent.h string.h \
                   sys/ioctl.h sys/mount.h sys/param.h sys/statvfs.h \
-                  sys/time.h sys/types.h sys/ucred.h syslog.h wchar.h])
+                  sys/time.h sys/types.h sys/ucred.h syslog.h termios.h \
+                  wchar.h])
 
 # Checks for typedefs, structures, and compiler characteristics.
 AC_C_INLINE
@@ -190,7 +191,7 @@ AC_FUNC_GETMNTENT
 AC_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK
 AC_FUNC_MKTIME
 AC_CHECK_FUNCS([geteuid getmntinfo realpath regcomp strcasecmp \
-                strndup strrchr strsep swprintf \
+                strndup strrchr strsep swprintf tcflush \
                 wcwidth uname])
 # For the diskspace code
 FS_STATS_TYPE
diff --git a/src/pacman/util.c b/src/pacman/util.c
index 53dbd637..0cb6a9f4 100644
--- a/src/pacman/util.c
+++ b/src/pacman/util.c
@@ -37,6 +37,9 @@
 #include <unistd.h>
 #include <limits.h>
 #include <wchar.h>
+#ifdef HAVE_TERMIOS_H
+#include <termios.h> /* tcflush */
+#endif
 
 #include <alpm.h>
 #include <alpm_list.h>
@@ -100,6 +103,18 @@ int needs_root(void)
 	}
 }
 
+/* discard unhandled input on the terminal's input buffer */
+static int flush_term_input(void) {
+#ifdef HAVE_TCFLUSH
+	if(isatty(fileno(stdin))) {
+		return(tcflush(fileno(stdin), TCIFLUSH));
+	}
+#endif
+
+	/* fail silently */
+	return 0;
+}
+
 /* gets the current screen column width */
 int getcols(int def)
 {
@@ -828,6 +843,8 @@ int multiselect_question(char *array, int count)
 			break;
 		}
 
+		flush_term_input();
+
 		if(fgets(response, response_len, stdin)) {
 			const size_t response_incr = 64;
 			/* handle buffer not being large enough to read full line case */
@@ -887,6 +904,8 @@ int select_question(int count)
 			break;
 		}
 
+		flush_term_input();
+
 		if(fgets(response, sizeof(response), stdin)) {
 			strtrim(response);
 			if(strlen(response) > 0) {
@@ -934,6 +953,8 @@ static int question(short preset, char *fmt, va_list args)
 	}
 
 	fflush(stream);
+	flush_term_input();
+
 	if(fgets(response, sizeof(response), stdin)) {
 		strtrim(response);
 		if(strlen(response) == 0) {