[src/trunk]: src/tests/usr.bin/xlint/lint1 tests/lint: analyze yesterday's bu...

[rillig <rillig%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/2da3150b8662
branches:  trunk
changeset: 984542:2da3150b8662
user:      rillig <rillig%NetBSD.org@localhost>
date:      Sun Jul 11 13:32:06 2021 +0000

description:
tests/lint: analyze yesterday's bug for parsing declarations

diffstat:

 tests/usr.bin/xlint/lint1/gcc_attribute_var.c   |  43 ++++++++++++++++++++++++-
 tests/usr.bin/xlint/lint1/gcc_attribute_var.exp |   4 +-
 2 files changed, 45 insertions(+), 2 deletions(-)

diffs (65 lines):

diff -r 00959f8ae2a8 -r 2da3150b8662 tests/usr.bin/xlint/lint1/gcc_attribute_var.c
--- a/tests/usr.bin/xlint/lint1/gcc_attribute_var.c     Sun Jul 11 13:00:52 2021 +0000
+++ b/tests/usr.bin/xlint/lint1/gcc_attribute_var.c     Sun Jul 11 13:32:06 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: gcc_attribute_var.c,v 1.1 2021/07/06 17:33:07 rillig Exp $     */
+/*     $NetBSD: gcc_attribute_var.c,v 1.2 2021/07/11 13:32:06 rillig Exp $     */
 # 3 "gcc_attribute_var.c"
 
 /*
@@ -23,6 +23,47 @@
     int after __attribute__((__deprecated__))
 );
 
+void println(void);
+
+/*
+ * Since cgram.y 1.294 from 2021-07-10, lint did not accept declarations that
+ * started with __attribute__, due to a newly and accidentally introduced
+ * shift/reduce conflict in the grammar.
+ *
+ * A GCC extension allows statement of the form __attribute__((fallthrough)),
+ * thus starting with __attribute__.  This is the 'shift' in the conflict.
+ * The 'reduce' in the conflict was begin_type.
+ *
+ * Before cgram 1.294, the gcc_attribute was placed outside the pair of
+ * begin_type/end_type, exactly to resolve this conflict.
+ *
+ * Conceptually, it made sense to put the __attribute__((unused)) between
+ * begin_type and end_type, to make it part of the declaration-specifiers.
+ * This change introduced the hidden conflict though.
+ *
+ * Interestingly, the number of shift/reduce conflicts did not change in
+ * cgram 1.294, the conflicts were just resolved differently than before.
+ *
+ * To prevent this from happening again, make sure that declarations as well
+ * as statements can start with gcc_attribute.
+ */
+void
+ambiguity_for_attribute(void)
+{
+       /*FIXME*//* expect+1: error: syntax error '_Bool' [249] */
+       __attribute__((unused)) _Bool var1;
+
+       switch (1) {
+       case 1:
+               println();
+               /*FIXME*//* expect+1: error: syntax error '_Bool' [249] */
+               __attribute__((unused)) _Bool var2;
+               __attribute__((fallthrough));
+               case 2:
+                       println();
+       }
+}
+
 /* just to trigger _some_ error, to keep the .exp file */
 /* expect+1: error: syntax error 'syntax_error' [249] */
 __attribute__((syntax_error));
diff -r 00959f8ae2a8 -r 2da3150b8662 tests/usr.bin/xlint/lint1/gcc_attribute_var.exp
--- a/tests/usr.bin/xlint/lint1/gcc_attribute_var.exp   Sun Jul 11 13:00:52 2021 +0000
+++ b/tests/usr.bin/xlint/lint1/gcc_attribute_var.exp   Sun Jul 11 13:32:06 2021 +0000
@@ -1,1 +1,3 @@
-gcc_attribute_var.c(28): error: syntax error 'syntax_error' [249]
+gcc_attribute_var.c(54): error: syntax error '_Bool' [249]
+gcc_attribute_var.c(60): error: syntax error '_Bool' [249]
+gcc_attribute_var.c(69): error: syntax error 'syntax_error' [249]