1 /* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
4
5 #include "KungFuDeathGripChecker.h"
6 #include "CustomMatchers.h"
7
registerMatchers(MatchFinder * AstMatcher)8 void KungFuDeathGripChecker::registerMatchers(MatchFinder *AstMatcher) {
9 AstMatcher->addMatcher(varDecl(hasType(isRefPtr())).bind("decl"), this);
10 }
11
check(const MatchFinder::MatchResult & Result)12 void KungFuDeathGripChecker::check(const MatchFinder::MatchResult &Result) {
13 const char *Error = "Unused \"kungFuDeathGrip\" %0 objects constructed from "
14 "%1 are prohibited";
15 const char *Note = "Please switch all accesses to this %0 to go through "
16 "'%1', or explicitly pass '%1' to `mozilla::Unused`";
17
18 const VarDecl *D = Result.Nodes.getNodeAs<VarDecl>("decl");
19 if (D->isReferenced() || !D->hasLocalStorage() || !D->hasInit()) {
20 return;
21 }
22
23 // Not interested in parameters.
24 if (isa<ImplicitParamDecl>(D) || isa<ParmVarDecl>(D)) {
25 return;
26 }
27
28 const Expr *E = IgnoreTrivials(D->getInit());
29 const CXXConstructExpr *CE = dyn_cast<CXXConstructExpr>(E);
30 if (CE && CE->getNumArgs() == 0) {
31 // We don't report an error when we construct and don't use a nsCOMPtr /
32 // nsRefPtr with no arguments. We don't report it because the error is not
33 // related to the current check. In the future it may be reported through a
34 // more generic mechanism.
35 return;
36 }
37
38 // We don't want to look at the single argument conversion constructors
39 // which are inbetween the declaration and the actual object which we are
40 // assigning into the nsCOMPtr/RefPtr. To do this, we repeatedly
41 // IgnoreTrivials, then look at the expression. If it is one of these
42 // conversion constructors, we ignore it and continue to dig.
43 while ((CE = dyn_cast<CXXConstructExpr>(E)) && CE->getNumArgs() == 1) {
44 E = IgnoreTrivials(CE->getArg(0));
45 }
46
47 // We allow taking a kungFuDeathGrip of `this` because it cannot change
48 // beneath us, so calling directly through `this` is OK. This is the same
49 // for local variable declarations.
50 //
51 // We also don't complain about unused RefPtrs which are constructed from
52 // the return value of a new expression, as these are required in order to
53 // immediately destroy the value created (which was presumably created for
54 // its side effects), and are not used as a death grip.
55 if (isa<CXXThisExpr>(E) || isa<DeclRefExpr>(E) || isa<CXXNewExpr>(E)) {
56 return;
57 }
58
59 // These types are assigned into nsCOMPtr and RefPtr for their side effects,
60 // and not as a kungFuDeathGrip. We don't want to consider RefPtr and nsCOMPtr
61 // types which are initialized with these types as errors.
62 const TagDecl *TD = E->getType()->getAsTagDecl();
63 if (TD && TD->getIdentifier()) {
64 static const char *IgnoreTypes[] = {
65 "already_AddRefed",
66 "nsGetServiceByCID",
67 "nsGetServiceByCIDWithError",
68 "nsGetServiceByContractID",
69 "nsGetServiceByContractIDWithError",
70 "nsCreateInstanceByCID",
71 "nsCreateInstanceByContractID",
72 "nsCreateInstanceFromFactory",
73 };
74
75 for (uint32_t i = 0; i < sizeof(IgnoreTypes) / sizeof(IgnoreTypes[0]);
76 ++i) {
77 if (TD->getName() == IgnoreTypes[i]) {
78 return;
79 }
80 }
81 }
82
83 // Report the error
84 const char *ErrThing;
85 const char *NoteThing;
86 if (isa<MemberExpr>(E)) {
87 ErrThing = "members";
88 NoteThing = "member";
89 } else {
90 ErrThing = "temporary values";
91 NoteThing = "value";
92 }
93
94 // We cannot provide the note if we don't have an initializer
95 diag(D->getLocStart(), Error, DiagnosticIDs::Error)
96 << D->getType() << ErrThing;
97 diag(E->getLocStart(), Note, DiagnosticIDs::Note)
98 << NoteThing << getNameChecked(D);
99 }
100