-AT_CHECK([bison -o input.c input.y])
-AT_COMPILE([input])
-AT_PARSER_CHECK([./input], 1,
-[[sending: 'x' (value = 0, line 0)
-thing(0@0): 'x'(0@0)
-sending: 'x' (value = 1, line 10)
-thing(1@10): 'x'(1@10)
-sending: 'x' (value = 2, line 20)
-thing(2@20): 'x'(2@20)
-sending: 'x' (value = 3, line 30)
-30: parse error, unexpected 'x', expecting ';'
-Freeing nterm thing (2@20)
-Freeing nterm thing (1@10)
-Freeing nterm thing (0@0)
-Freeing token 'x' (3@30)
-sending: 'x' (value = 4, line 40)
-Freeing token 'x' (4@40)
-sending: 'x' (value = 5, line 50)
-Freeing token 'x' (5@50)
-sending: ';' (value = 6, line 60)
-line(-1@50): error(@50) ';'
-sending: 'x' (value = 7, line 70)
-thing(7@70): 'x'(7@70)
-sending: 'x' (value = 8, line 80)
-thing(8@80): 'x'(8@80)
-sending: ';' (value = 9, line 90)
-line(7@70): thing(7@70) thing(8@80) ';'
-sending: 'x' (value = 10, line 100)
-thing(10@100): 'x'(10@100)
-sending: ';' (value = 11, line 110)
-line(10@100): thing(10@100) ';'
-sending: 'y' (value = 12, line 120)
-120: parse error, unexpected $undefined, expecting $end or 'x'
-sending: EOF
-Freeing nterm line (10@100)
-Freeing nterm line (7@70)
-Freeing nterm line (-1@50)
+AT_LALR1_CC_IF(
+ [AT_CHECK([bison -o input.cc input.y])
+ AT_COMPILE_CXX([input])],
+ [AT_CHECK([bison -o input.c input.y])
+ AT_COMPILE([input])])
+
+
+# Check the location of "empty"
+# -----------------------------
+# I.e., epsilon-reductions, as in "(x)" which ends by reducing
+# an empty "line" nterm.
+# FIXME: This location is not satisfying. Depend on the lookahead?
+AT_PARSER_CHECK([./input '(x)'], 0,
+[[sending: '(' (0@0-9)
+sending: 'x' (1@10-19)
+thing (1@10-19): 'x' (1@10-19)
+sending: ')' (2@20-29)
+line (0@0-29): '(' (0@0-9) thing (1@10-19) ')' (2@20-29)
+sending: EOF (3@30-39)
+input (0@29-29): /* Nothing */
+input (2@0-29): line (0@0-29) input (0@29-29)
+Successful parse.
+]])
+
+
+# Check locations in error recovery
+# ---------------------------------
+# '(y)' is an error, but can be recovered from. But what's the location
+# of the error itself ('y'), and of the resulting reduction ('(error)').
+AT_PARSER_CHECK([./input '(y)'], 0,
+[[sending: '(' (0@0-9)
+sending: 'y' (1@10-19)
+10-19: syntax error, unexpected 'y', expecting 'x'
+Freeing token 'y' (1@10-19)
+sending: ')' (2@20-29)
+line (-1@0-29): '(' (0@0-9) error (@10-19) ')' (2@20-29)
+sending: EOF (3@30-39)
+input (0@29-29): /* Nothing */
+input (2@0-29): line (-1@0-29) input (0@29-29)
+Successful parse.
+]])
+
+
+# Syntax errors caught by the parser
+# ----------------------------------
+# Exercise the discarding of stack top and input until `error'
+# can be reduced.
+#
+# '(', 'x', 'x', 'x', 'x', 'x', ')',
+#
+# Load the stack and provoke an error that cannot be caught by the
+# grammar, to check that the stack is cleared. And make sure the
+# lookahead is freed.
+#
+# '(', 'x', ')',
+# '(', 'x', ')',
+# 'y'
+AT_PARSER_CHECK([./input '(xxxxx)(x)(x)y'], 1,
+[[sending: '(' (0@0-9)
+sending: 'x' (1@10-19)
+thing (1@10-19): 'x' (1@10-19)
+sending: 'x' (2@20-29)
+thing (2@20-29): 'x' (2@20-29)
+sending: 'x' (3@30-39)
+30-39: syntax error, unexpected 'x', expecting ')'
+Freeing nterm thing (2@20-29)
+Freeing nterm thing (1@10-19)
+Freeing token 'x' (3@30-39)
+sending: 'x' (4@40-49)
+Freeing token 'x' (4@40-49)
+sending: 'x' (5@50-59)
+Freeing token 'x' (5@50-59)
+sending: ')' (6@60-69)
+line (-1@0-69): '(' (0@0-9) error (@10-59) ')' (6@60-69)
+sending: '(' (7@70-79)
+sending: 'x' (8@80-89)
+thing (8@80-89): 'x' (8@80-89)
+sending: ')' (9@90-99)
+line (7@70-99): '(' (7@70-79) thing (8@80-89) ')' (9@90-99)
+sending: '(' (10@100-109)
+sending: 'x' (11@110-119)
+thing (11@110-119): 'x' (11@110-119)
+sending: ')' (12@120-129)
+line (10@100-129): '(' (10@100-109) thing (11@110-119) ')' (12@120-129)
+sending: 'y' (13@130-139)
+input (0@129-129): /* Nothing */
+input (2@100-129): line (10@100-129) input (0@129-129)
+input (2@70-129): line (7@70-99) input (2@100-129)
+input (2@0-129): line (-1@0-69) input (2@70-129)
+130-139: syntax error, unexpected 'y', expecting $end
+Freeing nterm input (2@0-129)
+Freeing token 'y' (13@130-139)