* [pushed] Another Rust operator precedence bug
@ 2022-12-12 13:41 Tom Tromey
0 siblings, 0 replies; only message in thread
From: Tom Tromey @ 2022-12-12 13:41 UTC (permalink / raw)
To: gdb-patches; +Cc: Tom Tromey
My earlier patch to fix PR rust/29859 introduced a new operator
precedence bug in the Rust parser. Assignment operators are
right-associative in Rust. And, while this doesn't often matter, as
Rust assignments always have the value (), still as a matter of
principle we should get this correct.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29859
---
gdb/rust-parse.c | 10 ++++++++--
gdb/testsuite/gdb.rust/simple.exp | 3 +++
2 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/gdb/rust-parse.c b/gdb/rust-parse.c
index 337927219d5..f28514ab2da 100644
--- a/gdb/rust-parse.c
+++ b/gdb/rust-parse.c
@@ -1344,6 +1344,8 @@ rust_parser::parse_binop (bool required)
OPERATION (ANDAND, 2, logical_and_operation) \
OPERATION (OROR, 1, logical_or_operation)
+#define ASSIGN_PREC 0
+
operation_up start = parse_atom (required);
if (start == nullptr)
{
@@ -1376,7 +1378,7 @@ rust_parser::parse_binop (bool required)
compound_assign_op = current_opcode;
/* FALLTHROUGH */
case '=':
- precedence = 0;
+ precedence = ASSIGN_PREC;
lex ();
break;
@@ -1398,7 +1400,11 @@ rust_parser::parse_binop (bool required)
break;
}
- while (precedence <= operator_stack.back ().precedence
+ /* Make sure that assignments are right-associative while other
+ operations are left-associative. */
+ while ((precedence == ASSIGN_PREC
+ ? precedence < operator_stack.back ().precedence
+ : precedence <= operator_stack.back ().precedence)
&& operator_stack.size () > 1)
{
rustop_item rhs = std::move (operator_stack.back ());
diff --git a/gdb/testsuite/gdb.rust/simple.exp b/gdb/testsuite/gdb.rust/simple.exp
index 3a010f30ea6..0fb06af9380 100644
--- a/gdb/testsuite/gdb.rust/simple.exp
+++ b/gdb/testsuite/gdb.rust/simple.exp
@@ -416,3 +416,6 @@ if {[lindex $v 0] >= 8} {
# The new parser introduced an operator precedence bug.
gdb_test "print 5 * 7 / 5" " = 7"
gdb_test "print 4 - 3 - 1" " = 0"
+
+# Another operator precedence bug.
+gdb_test "print \$one = \$two = 75" " = \\\(\\\)"
--
2.38.1
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