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From: Tom de Vries <>
Subject: [binutils-gdb] [gdbsupport] Fix UB in
Date: Mon, 23 May 2022 12:50:17 +0000 (GMT)	[thread overview]
Message-ID: <> (raw);h=735dfe028c93f20026339f3eeeadacac82fe7963

commit 735dfe028c93f20026339f3eeeadacac82fe7963
Author: Tom de Vries <>
Date:   Mon May 23 14:50:02 2022 +0200

    [gdbsupport] Fix UB in
    When building gdb with -fsanitize=undefined, I run into:
    (gdb) PASS: gdb.ada/access_to_packed_array.exp: set logging enabled on
    maint print symbols^M error: negation of -9223372036854775808 cannot \
      be represented in type 'long int'; cast to an unsigned type to negate this \
      value to itself
    (gdb) FAIL: gdb.ada/access_to_packed_array.exp: maint print symbols
    By running in a debug session, we find that this happens during printing of:
       typedef system.storage_elements.storage_offset: \
         range -9223372036854775808 .. 9223372036854775807;
    Possibly, an ada test-case could be created that exercises this in isolation.
    The problem is here in int_string, where we negate a val with type LONGEST:
             return decimal2str ("-", -val, width);
    Fix this by, as recommend, using "-(ULONGEST)val" instead.
    Tested on x86_64-linux.

 gdbsupport/ | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/gdbsupport/ b/gdbsupport/
index 73ff1afda30..7bbb6deea74 100644
--- a/gdbsupport/
+++ b/gdbsupport/
@@ -278,7 +278,11 @@ int_string (LONGEST val, int radix, int is_signed, int width,
     case 10:
 	if (is_signed && val < 0)
-	  return decimal2str ("-", -val, width);
+	  /* Cast to unsigned before negating, to prevent runtime error:
+	     negation of -9223372036854775808 cannot be represented in type
+	     'long int'; cast to an unsigned type to negate this value to
+	     itself.  */
+	  return decimal2str ("-", -(ULONGEST)val, width);
 	  return decimal2str ("", val, width);

                 reply	other threads:[~2022-05-23 12:50 UTC|newest]

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