Fix $LINENO corruption when autoloading functions

Autoloading a function caused the calling script's $LINENO to be
off by the number of lines in the function definition file. In
addition, while running autoloaded functions, errors/warnings were
reported with wrong line numbers.

src/cmd/ksh93/sh/path.c:
- Save $LINENO (shp->inlineno) before autoloading a function, reset
  it to 1 so that the correct line number offset is remembered for
  the function definition, and restore it after.

src/cmd/ksh93/tests/variables.sh:
- Add regression test for $LINENO, directly and in error messages,
  within and outside a non-autoloaded and an autoloaded function.

Fixes: https://github.com/ksh93/ksh/issues/116

NEWS

@@ -14,6 +14,10 @@ Any uppercase BUG_* names are modernish shell bug IDs.
   nonzero exit status. Similarly, if both the 'errexit' and 'pipefail' options
   are active, ksh now correctly exits if any pipeline element returns nonzero.
 
+- Autoloading a function no longer causes the calling script's $LINENO to be
+  off by the number of lines in the function definition file that was loaded.
+  This also corrects line numbers in warnings and error messages.
+
 2020-09-28:
 
 - While executing a ksh-style function, ksh 93u+ ignored all signals for which

src/cmd/ksh93/sh/path.c

@@ -582,7 +582,7 @@ static void funload(Shell_t *shp,int fno, const char *name)
 	char		*pname,*oldname=shp->st.filename, buff[IOBSIZE+1];
 	Namval_t	*np;
 	struct Ufunction *rp,*rpfirst;
-	int		 savestates = sh_getstate(), oldload=shp->funload;
+	int		savestates = sh_getstate(), oldload=shp->funload, savelineno = shp->inlineno;
 	pname = path_fullname(shp,stakptr(PATH_OFFSET));
 	if(shp->fpathdict && (rp = dtmatch(shp->fpathdict,(void*)pname)))
 	{
@@ -615,6 +615,7 @@ static void funload(Shell_t *shp,int fno, const char *name)
 	shp->readscript = (char*)name;
 	shp->st.filename = pname;
 	shp->funload = 1;
+	shp->inlineno = 1;
 	error_info.line = 0;
 	sh_eval(sfnew(NIL(Sfio_t*),buff,IOBSIZE,fno,SF_READ),SH_FUNEVAL);
 	sh_close(fno);
@@ -631,6 +632,7 @@ static void funload(Shell_t *shp,int fno, const char *name)
 		pname = 0;
 	free((void*)shp->st.filename);
 	shp->funload = oldload;
+	shp->inlineno = savelineno;
 	shp->st.filename = oldname;
 	sh_setstate(savestates);
 	if(pname)

src/cmd/ksh93/tests/variables.sh

@@ -1130,5 +1130,52 @@ case $'\n'$(env 'BASH_FUNC_a%%=() { echo test; }' "$SHELL" -c set) in
 	err_exit 'ksh imports environment variables with invalid names' ;;
 esac
 
+# ======
+# Autoloading a function caused $LINENO to be off by the # of lines in the function definition file.
+# https://github.com/ksh93/ksh/issues/116
+
+cd "$tmp" || exit 128
+
+cat >lineno_autoload <<'EOF'
+echo "begin: main script \$LINENO == $LINENO"
+function main_script_fn
+{
+	lineno_autoload_fn
+	(: ${bad\subst\in\main_script_fn\on\line\5})
+}
+main_script_fn
+(eval 'syntax error(')
+(: ${bad\subst\in\main\script\on\line\9})
+echo "end: main script \$LINENO == $LINENO"
+EOF
+
+cat >lineno_autoload_fn <<'EOF'
+function lineno_autoload_fn
+{
+	echo "Hi, I'm a function! On line 3, my \$LINENO is $LINENO"
+	(: ${bad\subst\in\function\on\line\4})
+	(eval 'syntax error(')
+	echo "Hi, I'm still a function! On line 6, my \$LINENO is $LINENO"
+}
+echo "In definition file, outside function: \$LINENO on line 8 is $LINENO"
+: ${bad\subst\in\def\file\on\line\9}
+EOF
+
+exp="begin: main script \$LINENO == 1
+In definition file, outside function: \$LINENO on line 8 is 8
+./lineno_autoload[7]: main_script_fn: line 9: \${bad\subst\in\def\file\on\line\9}: bad substitution
+Hi, I'm a function! On line 3, my \$LINENO is 3
+./lineno_autoload[7]: main_script_fn[4]: lineno_autoload_fn: line 4: \${bad\subst\in\function\on\line\4}: bad substitution
+./lineno_autoload[7]: main_script_fn[4]: lineno_autoload_fn[5]: eval: syntax error at line 1: \`(' unexpected
+Hi, I'm still a function! On line 6, my \$LINENO is 6
+./lineno_autoload[7]: main_script_fn: line 5: \${bad\subst\in\main_script_fn\on\line\5}: bad substitution
+./lineno_autoload[8]: eval: syntax error at line 1: \`(' unexpected
+./lineno_autoload: line 9: \${bad\subst\in\main\script\on\line\9}: bad substitution
+end: main script \$LINENO == 10"
+
+got=$(FPATH=$tmp "$SHELL" ./lineno_autoload 2>&1)
+[[ $got == "$exp" ]] || err_exit 'Regression in \$LINENO and/or error messages.' \
+	$'Diff follows:\n'"$(diff -u <(print -r -- "$exp") <(print -r -- "$got") | sed $'s/^/\t| /')"
+
 # ======
 exit $((Errors<125?Errors:125))