From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Fri, 18 Apr 2025 13:03:56 +0000 (-0300)
Subject: stdio: Fix UB on snprintf
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5197a3a2f7118266b139653a45bd1e9900529091;p=thirdparty%2Fglibc.git

stdio: Fix UB on snprintf

The elf/tst-dl-printf-static test when built with ubsan triggers:

UBSAN: Undefined behaviour in vfprintf-process-arg.c:58:36 negation of 9223372036854775808 cannot be represented in type 'long int'
---

diff --git a/stdio-common/vfprintf-process-arg.c b/stdio-common/vfprintf-process-arg.c
index 90b5e61ceb..a41feb2c47 100644
--- a/stdio-common/vfprintf-process-arg.c
+++ b/stdio-common/vfprintf-process-arg.c
@@ -55,7 +55,8 @@ LABEL (form_integer):
         signed_number = (short int) process_arg_unsigned_int ();
 
       is_negative = signed_number < 0;
-      number.word = is_negative ? (- signed_number) : signed_number;
+      number.word = is_negative ? (- (unsigned long) signed_number)
+				: signed_number;
 
       goto LABEL (number);
     }