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Java: Improve NullGuards.clearlyNotNullExpr()
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+148
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5 files changed

+148
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‎java/ql/src/semmle/code/java/dataflow/NullGuards.qll

Lines changed: 25 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -44,21 +44,32 @@ Expr clearlyNotNullExpr(Expr reason) {
4444
or
4545
result instanceof ArrayCreationExpr and reason = result
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or
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result instanceof FunctionalExpr and reason = result
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or
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result instanceof TypeLiteral and reason = result
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or
4951
result instanceof ThisAccess and reason = result
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or
5153
result instanceof StringLiteral and reason = result
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or
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// Add and AssignAdd performing String concatenation never have null result
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result instanceof AddExpr and result.getType() instanceof TypeString and reason = result
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or
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result instanceof AssignAddExpr and result.getType() instanceof TypeString and reason = result
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or
5560
exists(Field f |
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result = f.getAnAccess() and
57-
(f.hasName("TRUE") or f.hasName("FALSE")) and
62+
f.hasName(["TRUE", "FALSE"]) and
5863
f.getDeclaringType().hasQualifiedName("java.lang", "Boolean") and
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reason = result
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)
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or
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result.getType() instanceof PrimitiveType and not result instanceof TypeAccess and reason = result
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or
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// Ignore RValue because that is covered by SsaVariable check below and correctly
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// reports the assigned value as 'reason'
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result instanceof CompileTimeConstantExpr and not result instanceof RValue and reason = result
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or
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result.(CastExpr).getExpr() = clearlyNotNullExpr(reason)
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or
6475
result.(AssignExpr).getSource() = clearlyNotNullExpr(reason)
@@ -70,6 +81,12 @@ Expr clearlyNotNullExpr(Expr reason) {
7081
(reason = r1 or reason = r2)
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)
7283
or
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exists(SwitchExpr s |
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s = result and
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s.getAResult() = clearlyNotNullExpr(reason) and
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forall(Expr resultExpr | resultExpr = s.getAResult() | resultExpr = clearlyNotNullExpr())
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)
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or
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exists(SsaVariable v, boolean branch, RValue rval, Guard guard |
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guard = directNullGuard(v, branch, false) and
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guard.controls(rval.getBasicBlock(), branch) and
@@ -104,10 +121,13 @@ predicate clearlyNotNull(SsaVariable v, Expr reason) {
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clearlyNotNull(captured, reason)
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)
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or
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exists(Field f |
108-
v.getSourceVariable().getVariable() = f and
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f.isFinal() and
110-
f.getInitializer() = clearlyNotNullExpr(reason)
124+
exists(Variable var |
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v.getSourceVariable().getVariable() = var and
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var.isFinal() and
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var.getAnAssignedValue() = clearlyNotNullExpr(reason) and
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forall(Expr assignedValue | assignedValue = var.getAnAssignedValue() |
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assignedValue = clearlyNotNullExpr()
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)
111131
)
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}
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‎java/ql/test/library-tests/null-guards/ClearlyNotNullExpr.expected

Lines changed: 25 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,25 @@
1+
| Test.java:12:13:12:24 | new Object(...) | Test.java:12:13:12:24 | new Object(...) |
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| Test.java:13:21:13:21 | 0 | Test.java:13:21:13:21 | 0 |
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| Test.java:14:13:14:16 | this | Test.java:14:13:14:16 | this |
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| Test.java:15:13:15:14 | "" | Test.java:15:13:15:14 | "" |
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| Test.java:17:13:17:24 | Boolean.TRUE | Test.java:17:13:17:24 | Boolean.TRUE |
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| Test.java:18:13:18:25 | Boolean.FALSE | Test.java:18:13:18:25 | Boolean.FALSE |
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| Test.java:20:13:20:13 | 1 | Test.java:20:13:20:13 | 1 |
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| Test.java:21:13:21:21 | Float.NaN | Test.java:21:13:21:21 | Float.NaN |
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| Test.java:22:13:22:20 | constant | Test.java:3:29:3:30 | "" |
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| Test.java:23:13:23:23 | (...)... | Test.java:23:22:23:23 | "" |
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| Test.java:24:13:24:21 | ...=... | Test.java:24:20:24:21 | "" |
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| Test.java:26:13:26:54 | ...?...:... | Test.java:26:38:26:39 | "" |
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| Test.java:26:13:26:54 | ...?...:... | Test.java:26:43:26:54 | new Object(...) |
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| Test.java:27:13:27:21 | switch (...) | Test.java:3:29:3:30 | "" |
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| Test.java:27:13:27:21 | switch (...) | Test.java:28:27:28:28 | "" |
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| Test.java:34:13:34:25 | ...::... | Test.java:34:13:34:25 | ...::... |
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| Test.java:35:13:35:27 | ...->... | Test.java:35:13:35:27 | ...->... |
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| Test.java:41:13:41:18 | ... + ... | Test.java:41:13:41:18 | ... + ... |
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| Test.java:42:13:42:20 | ... + ... | Test.java:42:13:42:20 | ... + ... |
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| Test.java:43:13:43:19 | ...+=... | Test.java:43:13:43:19 | ...+=... |
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| Test.java:44:13:44:32 | ... + ... | Test.java:44:13:44:32 | ... + ... |
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| Test.java:51:17:51:18 | n1 | Test.java:49:13:49:22 | ... != ... |
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| Test.java:59:13:59:14 | n2 | Test.java:57:14:57:15 | "" |
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| Test.java:70:13:70:14 | n3 | Test.java:65:18:65:19 | "" |
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| Test.java:70:13:70:14 | n3 | Test.java:67:18:67:18 | 1 |

‎java/ql/test/library-tests/null-guards/ClearlyNotNullExpr.ql

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,9 @@
1+
import java
2+
import semmle.code.java.dataflow.NullGuards
3+
4+
from Expr notNull, Expr reason
5+
where
6+
notNull = clearlyNotNullExpr(reason) and
7+
// Restrict to ArrayInit to make results easier to read
8+
notNull.getParent() instanceof ArrayInit
9+
select notNull, reason

‎java/ql/test/library-tests/null-guards/Test.java

Lines changed: 88 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,88 @@
1+
class NonNullTest {
2+
final String constantNull = null;
3+
final String constant = "";
4+
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Object getMaybeNull() {
6+
return null;
7+
}
8+
9+
void notNull() {
10+
Object temp;
11+
Object[] r = {
12+
new Object(),
13+
new int[0],
14+
this,
15+
"",
16+
17+
Boolean.TRUE,
18+
Boolean.FALSE,
19+
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1,
21+
Float.NaN,
22+
constant,
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(Object) "",
24+
temp = "",
25+
26+
getMaybeNull() == null ? "" : new Object(),
27+
switch(1) {
28+
case 1 -> "";
29+
default -> constant;
30+
}
31+
};
32+
33+
Runnable[] functional = {
34+
this::notNull,
35+
() -> notNull()
36+
};
37+
38+
String s = null;
39+
String s2 = null;
40+
r = new Object[] {
41+
s + s2,
42+
null + s,
43+
s += s2,
44+
(String) null + null
45+
};
46+
47+
Object n1 = getMaybeNull();
48+
// Guarded by null check
49+
if (n1 != null) {
50+
r = new Object[] {
51+
n1
52+
};
53+
}
54+
55+
Object n2 = getMaybeNull();
56+
// Assigned a non-null value
57+
n2 = "";
58+
r = new Object[] {
59+
n2
60+
};
61+
62+
// final variable for which all assigned values are non-null
63+
final Object n3;
64+
if (getMaybeNull() == null) {
65+
n3 = "";
66+
} else {
67+
n3 = 1;
68+
}
69+
r = new Object[] {
70+
n3
71+
};
72+
}
73+
74+
void maybeNull(boolean b, int i) {
75+
Object temp;
76+
Object[] r = {
77+
constantNull,
78+
(Object) null,
79+
temp = (String) null,
80+
b ? "" : null,
81+
switch(i) {
82+
case 1 -> "";
83+
default -> null;
84+
},
85+
null
86+
};
87+
}
88+
}

‎java/ql/test/library-tests/null-guards/options

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
1+
//semmle-extractor-options: --javac-args -source 15 -target 15

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