From: Tom de Vries <tdevries@suse.de>
To: gdb-patches@sourceware.org
Subject: [PATCH 1/2] [gdb/exp] Fix UB in scalar_binop
Date: Tue, 17 May 2022 17:40:47 +0200 [thread overview]
Message-ID: <20220517154048.13213-1-tdevries@suse.de> (raw)
When building gdb with -fsanitize=undefined, I run into:
...
$ gdb -q -batch -ex "p -(-0x7fffffffffffffff - 1)"
src/gdb/valarith.c:1385:10: runtime error: signed integer overflow: \
0 - -9223372036854775808 cannot be represented in type 'long int'
$1 = -9223372036854775808
...
Fix this by performing the substraction in scalar_binop using unsigned types.
Tested on x86_64-linux.
---
gdb/testsuite/gdb.base/arithmet.exp | 2 ++
gdb/valarith.c | 5 ++++-
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/gdb/testsuite/gdb.base/arithmet.exp b/gdb/testsuite/gdb.base/arithmet.exp
index b6009a36235..4905c2e2706 100644
--- a/gdb/testsuite/gdb.base/arithmet.exp
+++ b/gdb/testsuite/gdb.base/arithmet.exp
@@ -98,3 +98,5 @@ gdb_test "print x-(y+w)" "3"
gdb_test "print x/(y*w)" "0"
gdb_test "print x-(y/w)" "9"
gdb_test "print (x+y)*w" "42"
+
+gdb_test "p /x -(-0x7fffffffffffffff - 1)" " = 0x8000000000000000"
diff --git a/gdb/valarith.c b/gdb/valarith.c
index 6210267826e..526cc02599e 100644
--- a/gdb/valarith.c
+++ b/gdb/valarith.c
@@ -1382,7 +1382,10 @@ scalar_binop (struct value *arg1, struct value *arg2, enum exp_opcode op)
break;
case BINOP_SUB:
- v = v1 - v2;
+ /* Avoid runtime error: signed integer overflow: \
+ 0 - -9223372036854775808 cannot be represented in type
+ 'long int'. */
+ v = (ULONGEST)v1 - (ULONGEST)v2;
break;
case BINOP_MUL:
base-commit: a1f2ddd38378c8db63e75daa28b7e304c2fd774f
--
2.35.3
next reply other threads:[~2022-05-17 15:40 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-17 15:40 Tom de Vries [this message]
2022-05-17 15:40 ` [PATCH 2/2] [gdbsupport] Fix UB in print-utils.cc:int_string Tom de Vries
2022-05-23 13:06 ` [committed][PATCH " Tom de Vries
2022-05-23 13:04 ` [committed][PATCH 1/2] [gdb/exp] Fix UB in scalar_binop Tom de Vries
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