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[gdb/exp] Fix UB in scalar_binop

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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.
This commit is contained in:
Tom de Vries
2022-05-23 14:50:02 +02:00
parent 05527d8ca1
commit 5a3cf18c2e
2 changed files with 6 additions and 1 deletions
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2
gdb/testsuite/gdb.base/arithmet.exp
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@ -98,3 +98,5 @@ gdb_test "print x-(y+w)" "3"
gdb_test "print x/(y*w)" "0" gdb_test "print x/(y*w)" "0"
gdb_test "print x-(y/w)" "9" gdb_test "print x-(y/w)" "9"
gdb_test "print (x+y)*w" "42" gdb_test "print (x+y)*w" "42"
gdb_test "p /x -(-0x7fffffffffffffff - 1)" " = 0x8000000000000000"

5
gdb/valarith.c
View File

@ -1382,7 +1382,10 @@ scalar_binop (struct value *arg1, struct value *arg2, enum exp_opcode op)
break; break;
case BINOP_SUB: 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; break;
case BINOP_MUL: case BINOP_MUL: