Disable broken KEYBD trap for multibyte characters

In UTF-8 locales, ksh breaks when a KEYBD trap is active, even a
dummy no-op one like 'trap : KEYBD'. Entering multi-byte characters
fails (the input is interrupted and a new prompt is displayed) and
pasting content with multi-byte characters produces corrupted
results.

The cause is that the KEYBD trap code is not multibyte-ready.
Unfortunately nobody yet understands the edit.c code well enough
to implement a proper fix. Pending that, this commit implements
a workaround that at least avoids breaking the shell.

src/cmd/ksh93/edit/edit.c: ed_getchar():
- When a multi-byte locale is active, do not trigger the the KEYBD
  trap except for ASCII characters (1-127).

Resolves: #307

NEWS

@@ -3,6 +3,12 @@ For full details, see the git log at: https://github.com/ksh93/ksh
 
 Any uppercase BUG_* names are modernish shell bug IDs.
 
+2022-02-12:
+
+- In multibyte locales such as UTF-8, shell input is no longer corrupted when
+  a KEYBD trap is active. However, the KEYBD trap is not yet multibyte ready
+  and is now only triggered for ASCII characters (1-127) in a multibyte locale.
+
 2022-02-11:
 
 - On the interactive shell, tab/esc completion is no longer disabled as a side

src/cmd/ksh93/edit/edit.c

@@ -1122,7 +1122,10 @@ int ed_getchar(register Edit_t *ep,int mode)
 				killpg(getpgrp(),SIGINT);
 				siglongjmp(ep->e_env, UINTR);
 			}
-			if(mode<=0 && sh.st.trap[SH_KEYTRAP])
+			if(mode<=0 && sh.st.trap[SH_KEYTRAP]
+			/* workaround for <https://github.com/ksh93/ksh/issues/307>:
+			 * do not trigger KEYBD for non-ASCII in multibyte locale */
+			&& (CC_NATIVE!=CC_ASCII || !mbwide() || c > -128))
 			{
 				ep->e_keytrap = 1;
 				n=1;

src/cmd/ksh93/include/version.h

@@ -21,7 +21,7 @@
 
 #define SH_RELEASE_FORK	"93u+m"		/* only change if you develop a new ksh93 fork */
 #define SH_RELEASE_SVER	"1.1.0-alpha"	/* semantic version number: https://semver.org */
-#define SH_RELEASE_DATE	"2022-02-11"	/* must be in this format for $((.sh.version)) */
+#define SH_RELEASE_DATE	"2022-02-12"	/* must be in this format for $((.sh.version)) */
 #define SH_RELEASE_CPYR	"(c) 2020-2022 Contributors to ksh " SH_RELEASE_FORK
 
 /* Scripts sometimes field-split ${.sh.version}, so don't change amount of whitespace. */

src/cmd/ksh93/sh.1

@@ -9062,6 +9062,10 @@ Thus, a trap on
 .B CHLD
 won't be executed until the foreground job terminates.
 .PP
+In locales that use a multibyte character set such as UTF-8, the
+.B KEYBD
+trap is only triggered for ASCII characters (1-127).
+.PP
 It is a good idea to leave a space after the comma operator in
 arithmetic expressions to prevent the comma from being interpreted
 as the decimal point character in certain locales.