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From: Tom de Vries <vries@sourceware.org> To: gdb-cvs@sourceware.org Subject: [binutils-gdb] [gdb/exp] Fix UB in scalar_binop Date: Mon, 23 May 2022 12:50:12 +0000 (GMT) [thread overview] Message-ID: <20220523125012.B5CAF38F861C@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=5a3cf18c2ed9593f194ea22f50ea5651532f6cfc commit 5a3cf18c2ed9593f194ea22f50ea5651532f6cfc Author: Tom de Vries <tdevries@suse.de> Date: Mon May 23 14:50:02 2022 +0200 [gdb/exp] Fix UB in scalar_binop 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. Diff: --- 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:
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